Human Health and Diseases - Question Paper

Unit 3: Biology and Human Welfare - Chapter 1

Section A: Multiple Choice Questions (MCQs) - 100 Questions

Instructions: Choose the correct answer from the given options.

According to WHO, health is defined as: a) Absence of disease b) Physical well-being only c) Complete physical, mental, and social well-being d) Mental stability
Which of the following is NOT a pathogen? a) Bacteria b) Viruses c) Antibodies d) Fungi
Rhinovirus causes: a) Pneumonia b) Common cold c) Typhoid d) Malaria
Dengue fever is transmitted by: a) Anopheles mosquito b) Culex mosquito c) Aedes aegypti mosquito d) Housefly
The Widal test is used to diagnose: a) Malaria b) Typhoid c) Dengue d) AIDS
Streptococcus pneumoniae causes: a) Typhoid b) Pneumonia c) Plague d) Cholera
Yersinia pestis is the causative agent of: a) Typhoid b) Pneumonia c) Plague d) Tuberculosis
Entamoeba histolytica causes: a) Malaria b) Amoebiasis c) Filariasis d) Ascariasis
The most severe form of malaria is caused by: a) Plasmodium vivax b) Plasmodium malariae c) Plasmodium ovale d) Plasmodium falciparum
Sporozoites are the infective stage of: a) Entamoeba b) Plasmodium c) Ascaris d) Wuchereria
Ascaris lumbricoides is a: a) Protozoan b) Bacterium c) Roundworm d) Flatworm
Elephantiasis is caused by: a) Ascaris lumbricoides b) Wuchereria bancrofti c) Entamoeba histolytica d) Plasmodium vivax
Ringworm is caused by: a) Virus b) Bacteria c) Fungi d) Protozoa
Innate immunity is: a) Acquired after birth b) Pathogen-specific c) Present from birth d) Slow but long-lasting
Which cells are involved in phagocytosis? a) B-cells b) T-cells c) Neutrophils and macrophages d) Plasma cells
Interferons are produced by: a) Bacteria b) Virus-infected cells c) Fungi d) Protozoa
Active immunity is: a) Fast but short-lived b) Slow but long-lasting c) Only natural d) Only artificial
Passive immunity is provided by: a) Vaccination b) Infection c) Ready-made antibodies d) Memory cells
Humoral immunity is mediated by: a) T-cells b) B-cells c) Macrophages d) NK cells
Cell-mediated immunity is responsible for: a) Antibody production b) Graft rejection c) Allergic reactions d) Phagocytosis
Antibodies are produced by: a) T-cells b) B-cells c) Macrophages d) NK cells
The most abundant antibody in serum is: a) IgG b) IgA c) IgM d) IgE
Which antibody is found in colostrum? a) IgG b) IgA c) IgM d) IgE
The largest antibody is: a) IgG b) IgA c) IgM d) IgE
IgE is involved in: a) Primary immune response b) Passive immunity c) Allergic reactions d) Graft rejection
Vaccines contain: a) Antibodies b) Antigens c) Complement proteins d) Interferons
HIV is a: a) DNA virus b) RNA virus (retrovirus) c) Bacterium d) Protozoan
HIV primarily attacks: a) B-cells b) Helper T-cells c) Macrophages d) NK cells
The enzyme used by HIV for reverse transcription is: a) DNA polymerase b) RNA polymerase c) Reverse transcriptase d) Ligase
ELISA test is used to diagnose: a) Cancer b) AIDS c) Diabetes d) Tuberculosis
HIV can be transmitted through: a) Mosquito bite b) Sharing food c) Sexual contact d) Coughing
Malignant tumors are characterized by: a) Slow growth b) Confined to original location c) Metastasis d) Harmless nature
Benign tumors: a) Spread to other parts b) Are cancerous c) Show metastasis d) Remain confined to original location
X-rays and gamma rays are examples of: a) Chemical carcinogens b) Physical carcinogens c) Biological carcinogens d) Oncogenes
Which virus is associated with cancer? a) HIV b) HPV c) Rhinovirus d) Dengue virus
Biopsy is used for: a) Cancer diagnosis b) AIDS diagnosis c) Malaria diagnosis d) Typhoid diagnosis
Chemotherapy causes: a) Hair growth b) Hair loss c) Weight gain d) Increased appetite
Immunotherapy uses: a) Antibiotics b) Biological response modifiers c) Surgery d) Radiation
Allergy is caused by: a) Lack of antibodies b) Exaggerated immune response c) Bacterial infection d) Viral infection
IgE antibodies are involved in: a) Bacterial infections b) Viral infections c) Allergic reactions d) Fungal infections
Histamine is released by: a) B-cells b) T-cells c) Mast cells d) Plasma cells
Antihistamines are used to treat: a) Bacterial infections b) Viral infections c) Allergic reactions d) Fungal infections
Morphine is derived from: a) Cannabis plant b) Coca plant c) Opium poppy d) Tobacco plant
Heroin is also known as: a) Coke b) Crack c) Smack d) Ganja
Marijuana is obtained from: a) Papaver somniferum b) Cannabis sativa c) Erythroxylum coca d) Nicotiana tabacum
Cocaine is obtained from: a) Opium poppy b) Cannabis plant c) Coca plant d) Tobacco plant
Opioids bind to: a) Dopamine receptors b) Opioid receptors c) Cannabinoid receptors d) Serotonin receptors
Cocaine interferes with: a) Dopamine transport b) Serotonin transport c) GABA transport d) Acetylcholine transport
Long-term alcohol abuse causes: a) Lung cancer b) Liver cirrhosis c) Kidney stones d) Bone fractures
Withdrawal symptoms occur due to: a) Overdose b) Drug dependence c) Allergic reaction d) Infection
Chikungunya is transmitted by: a) Anopheles mosquito b) Culex mosquito c) Aedes mosquito d) Sandfly
Hemozoin is a toxin released during: a) Typhoid b) Malaria c) Dengue d) Chikungunya
Natural killer cells are part of: a) Adaptive immunity b) Innate immunity c) Humoral immunity d) Cell-mediated immunity
Memory cells are formed during: a) Primary immune response b) Innate immunity c) Allergic reactions d) Autoimmune diseases
Vaccination provides: a) Passive immunity b) Active immunity c) Innate immunity d) Natural immunity
Colostrum provides: a) Active immunity b) Passive immunity c) Innate immunity d) Cell-mediated immunity
Antivenom is an example of: a) Active immunity b) Passive immunity c) Innate immunity d) Cell-mediated immunity
Western blot is used as: a) Primary test for AIDS b) Confirmatory test for AIDS c) Treatment for AIDS d) Prevention of AIDS
Oncogenes are: a) Tumor suppressor genes b) Genes that cause cancer c) Normal genes d) Viral genes only
Metastasis refers to: a) Tumor growth b) Tumor spread c) Tumor shrinkage d) Tumor death
Radiotherapy is used for: a) Diagnosis of cancer b) Treatment of cancer c) Prevention of cancer d) Screening for cancer
Alpha-interferon is used in: a) Chemotherapy b) Radiotherapy c) Immunotherapy d) Surgery
Asthma is caused by: a) Bacterial infection b) Viral infection c) Allergic reaction d) Fungal infection
Adrenaline is used to treat: a) Bacterial infections b) Viral infections c) Severe allergic reactions d) Fungal infections
LSD is a: a) Stimulant b) Depressant c) Hallucinogen d) Analgesic
Barbiturates are: a) Stimulants b) Sedatives c) Hallucinogens d) Analgesics
The infective stage of Ascaris is: a) Egg b) Larva c) Adult worm d) Cyst
Culex mosquito transmits: a) Malaria b) Dengue c) Filariasis d) Chikungunya
Droplet infection is seen in: a) Malaria b) Filariasis c) Pneumonia d) Amoebiasis
Flea bite transmits: a) Malaria b) Dengue c) Plague d) Typhoid
Microsporum causes: a) Athlete's foot b) Ringworm c) Pneumonia d) Typhoid
Intense itching is a symptom of: a) Typhoid b) Malaria c) Ringworm d) Pneumonia
Lymphatic vessels are affected in: a) Ascariasis b) Filariasis c) Amoebiasis d) Malaria
Genital organs may be affected in: a) Malaria b) Typhoid c) Filariasis d) Pneumonia
Intestinal perforation can occur in: a) Malaria b) Typhoid c) Dengue d) Pneumonia
Greyish-blue color of lips indicates: a) Anemia b) Lack of oxygen c) Fever d) Infection
Buboes are swollen: a) Liver b) Spleen c) Lymph nodes d) Kidneys
Pneumonic plague affects: a) Skin b) Lymph nodes c) Lungs d) Intestines
Constipation is a symptom of: a) Malaria b) Typhoid c) Dengue d) Pneumonia
Blood clots in stool indicate: a) Malaria b) Typhoid c) Amoebiasis d) Pneumonia
Enlarged spleen is seen in: a) Typhoid b) Malaria c) Dengue d) All of the above
Recurring fever is characteristic of: a) Typhoid b) Malaria c) Dengue d) Pneumonia
Severe joint pain is seen in: a) Malaria b) Dengue c) Chikungunya d) Typhoid
Pain behind eyes is seen in: a) Malaria b) Dengue c) Typhoid d) Pneumonia
Muscular pain is a symptom of: a) Typhoid b) Ascariasis c) Pneumonia d) Ringworm
Anemia can be caused by: a) Malaria b) Ascariasis c) Hookworm infection d) All of the above
Blockage of intestinal passage occurs in: a) Malaria b) Ascariasis c) Filariasis d) Amoebiasis
Gross deformities of limbs occur in: a) Malaria b) Ascariasis c) Filariasis d) Amoebiasis
Dry scaly lesions are seen in: a) Malaria b) Ringworm c) Typhoid d) Pneumonia
Nails and scalp are affected in: a) Malaria b) Ringworm c) Typhoid d) Pneumonia
Contaminated food and water transmit: a) Malaria b) Typhoid c) Dengue d) Filariasis
Mosquito control prevents: a) Typhoid b) Malaria c) Pneumonia d) Ringworm
Personal hygiene prevents: a) Malaria b) Dengue c) Ringworm d) Pneumonia
Vaccination prevents: a) Typhoid b) Pneumonia c) Plague d) All of the above
Rodent control prevents: a) Malaria b) Dengue c) Plague d) Typhoid
Mosquito nets prevent: a) Typhoid b) Malaria c) Pneumonia d) Ringworm
Avoid sharing personal items to prevent: a) Malaria b) Ringworm c) Typhoid d) Pneumonia
Proper sanitation prevents: a) Malaria b) Typhoid c) Dengue d) Pneumonia
Antimalarial drugs are used for: a) Treatment of malaria b) Prevention of malaria c) Both a and b d) None of the above
Safe drinking water prevents: a) Malaria b) Typhoid c) Dengue d) Pneumonia

Section B: Short Answer Questions (1 Mark Each) - 100 Questions

Instructions: Answer in one word or one sentence.

What does WHO stand for?
Define pathogen.
Name the causative agent of common cold.
Which mosquito transmits dengue fever?
Name the diagnostic test for typhoid.
What causes pneumonia?
Name the causative agent of plague.
What is the causative agent of amoebiasis?
Which is the most severe form of malaria?
What is the infective stage of Plasmodium?
Name the roundworm that causes ascariasis.
What causes elephantiasis?
Name three fungi that cause ringworm.
What is innate immunity?
Name two phagocytic cells.
What are interferons?
Define active immunity.
What is passive immunity?
Which cells mediate humoral immunity?
What is cell-mediated immunity responsible for?
What are antibodies also called?
Which is the most abundant antibody in serum?
Where is IgA found?
Which is the largest antibody?
What is IgE involved in?
What do vaccines contain?
What type of virus is HIV?
Which cells does HIV primarily attack?
Name the enzyme used by HIV for reverse transcription.
What test is used to diagnose AIDS?
Name one mode of HIV transmission.
What characterizes malignant tumors?
What are benign tumors?
Give an example of physical carcinogen.
Name a virus associated with cancer.
What is biopsy used for?
What is a side effect of chemotherapy?
What does immunotherapy use?
What causes allergy?
Which antibody is involved in allergic reactions?
Which cells release histamine?
What are antihistamines used for?
Which plant gives morphine?
What is heroin also called?
Which plant gives marijuana?
From which plant is cocaine obtained?
Where do opioids bind?
What does cocaine interfere with?
What does long-term alcohol abuse cause?
When do withdrawal symptoms occur?
Which mosquito transmits chikungunya?
What is hemozoin?
What are natural killer cells part of?
When are memory cells formed?
What type of immunity does vaccination provide?
What type of immunity does colostrum provide?
What is an example of passive immunity?
What is Western blot used for?
What are oncogenes?
What does metastasis refer to?
What is radiotherapy used for?
What is alpha-interferon used in?
What causes asthma?
What is adrenaline used for?
What type of drug is LSD?
What are barbiturates?
What is the infective stage of Ascaris?
Which mosquito transmits filariasis?
What is droplet infection?
What transmits plague?
What does Microsporum cause?
What is a symptom of ringworm?
What is affected in filariasis?
What organs may be affected in filariasis?
What complication can occur in typhoid?
What does greyish-blue color of lips indicate?
What are buboes?
What does pneumonic plague affect?
What is a symptom of typhoid?
What indicates amoebiasis?
What is seen in malaria?
What is characteristic of malaria?
What is seen in chikungunya?
What is seen in dengue?
What is a symptom of ascariasis?
What can cause anemia?
What occurs in severe ascariasis?
What occurs in filariasis?
What are seen in ringworm?
What is affected in ringworm?
How is typhoid transmitted?
What prevents malaria?
What prevents ringworm?
What prevents typhoid?
What prevents plague?
What prevents malaria at night?
How to prevent ringworm?
What prevents waterborne diseases?
What are antimalarial drugs used for?
What prevents typhoid and amoebiasis?

Section C: Short Answer Questions (2 Marks Each) - 100 Questions

Instructions: Answer in 2-3 sentences.

Define health according to WHO.
List any four types of pathogens with examples.
Describe the transmission and symptoms of common cold.
Explain the cause and transmission of dengue fever.
What is the Widal test and what does it diagnose?
Describe the cause and symptoms of pneumonia.
Explain the transmission and symptoms of plague.
Describe the cause and symptoms of amoebiasis.
List the four species of Plasmodium and identify the most severe one.
What are sporozoites and where are they found?
Describe the cause and symptoms of ascariasis.
Explain the cause and symptoms of filariasis.
List three fungi that cause ringworm and describe its symptoms.
Differentiate between innate and acquired immunity.
Describe the physical barriers of innate immunity.
What are interferons and what is their function?
Differentiate between active and passive immunity.
Explain natural and artificial active immunity with examples.
Describe humoral immunity and the cells involved.
What is cell-mediated immunity and what is it responsible for?
Describe the structure of antibodies.
List the five types of antibodies and their functions.
Where is IgA found and what is its function?
Which antibody is involved in allergic reactions and why?
Explain the principle of immunization.
What are vaccines and how do they work?
Describe HIV and its type.
Which cells does HIV attack and why?
Explain the role of reverse transcriptase in HIV replication.
Describe the ELISA test and its use.
List three modes of HIV transmission.
Differentiate between benign and malignant tumors.
What is metastasis and which tumors show it?
List three types of carcinogens with examples.
Name two viruses associated with cancer.
Describe biopsy and its importance in cancer diagnosis.
What is chemotherapy and what are its side effects?
Explain immunotherapy and give an example.
What is allergy and what causes it?
Describe the mechanism of allergic reactions.
Which cells release histamine and when?
How are allergic reactions treated?
Describe morphine and its source.
What is heroin and what are its effects?
Describe marijuana and its source.
What is cocaine and what are its effects?
Explain the mechanism of action of opioids.
How does cocaine affect the nervous system?
What are the long-term effects of alcohol abuse?
What are withdrawal symptoms and when do they occur?
Compare the transmission of chikungunya and dengue.
What is hemozoin and what does it cause?
Describe natural killer cells and their function.
What are memory cells and when are they formed?
How does vaccination provide immunity?
How does colostrum provide immunity to infants?
Give two examples of passive immunity.
What is Western blot and when is it used?
What are oncogenes and how do they cause cancer?
Describe the process of metastasis.
How does radiotherapy work in cancer treatment?
What is alpha-interferon and how is it used?
Describe the mechanism of asthma.
When is adrenaline used in treating allergies?
What is LSD and what are its effects?
What are barbiturates and their effects?
Describe the life cycle of Ascaris briefly.
Compare the mosquito vectors of malaria and filariasis.
What is droplet infection and which diseases spread this way?
How is plague transmitted and what are its symptoms?
What fungi cause ringworm and how does it spread?
Describe the symptoms of ringworm infection.
What part of the body is affected in filariasis?
Which organs can be affected in chronic filariasis?
What serious complication can occur in typhoid?
What does cyanosis indicate in pneumonia patients?
What are buboes and in which disease are they seen?
Compare bubonic and pneumonic plague.
List four symptoms of typhoid fever.
How is amoebiasis diagnosed from stool examination?
What changes occur in the spleen during malaria?
Why does fever recur in malaria?
What are the characteristic symptoms of chikungunya?
Describe the eye symptoms in dengue fever.
How does ascariasis cause anemia?
What are the complications of heavy ascariasis?
Why does intestinal blockage occur in ascariasis?
Describe the deformities seen in chronic filariasis.
What type of lesions are seen in ringworm?
Which parts of the body are commonly affected by ringworm?
How can typhoid be prevented?
List four methods of malaria prevention.
How can ringworm be prevented?
What vaccines are available for bacterial diseases?
How can plague be prevented?
Why are mosquito nets effective against malaria?
What personal hygiene measures prevent ringworm?
How does proper sanitation prevent diseases?
What is the role of antimalarial drugs in prevention?
Why is safe drinking water important for health?

Section D: Long Answer Questions (3 Marks Each) - 100 Questions

Instructions: Answer in 4-6 sentences with proper explanations.

Define health according to WHO and explain why it's not just the absence of disease.
Classify pathogens into five categories with two examples each and their characteristics.
Describe the common cold in detail including cause, transmission, symptoms, and prevention.
Explain dengue fever comprehensively covering causative agent, vector, symptoms, and prevention methods.
Discuss the Widal test including its principle, procedure, and significance in typhoid diagnosis.
Describe pneumonia in detail including causative agents, transmission, symptoms, and prevention.
Explain plague comprehensively including causative agent, transmission modes, symptoms, and prevention.
Discuss amoebiasis in detail covering causative agent, transmission, symptoms, and prevention measures.
Describe the four species of Plasmodium, their distribution, and explain why P. falciparum is most dangerous.
Explain the concept of sporozoites, their formation, and their role in malaria transmission.
Describe ascariasis comprehensively including causative agent, transmission, symptoms, and prevention.
Explain filariasis in detail covering causative agents, vector, symptoms, and prevention methods.
Discuss ringworm including causative fungi, transmission, symptoms, and prevention measures.
Compare and contrast innate and acquired immunity with examples and characteristics.
Describe the four types of barriers in innate immunity with examples of each.
Explain interferons including their production, mechanism of action, and significance.
Differentiate between active and passive immunity with examples and explain their characteristics.
Describe the four types of acquired immunity with examples and their mechanisms.
Explain humoral immunity including the cells involved, mechanism, and significance.
Describe cell-mediated immunity including the cells involved and its functions.
Explain the structure of antibodies in detail including heavy and light chains.
Describe the five types of immunoglobulins with their locations and functions.
Explain the role of IgA in mucosal immunity and its importance.
Describe the role of IgE in allergic reactions and parasitic infections.
Explain the principle of immunization and how vaccines provide long-term protection.
Describe vaccines including their types, mechanism of action, and importance in disease prevention.
Explain HIV as a retrovirus including its structure and genetic material.
Describe why HIV specifically targets helper T-cells and the consequences.
Explain the role of reverse transcriptase in HIV replication and its significance.
Describe the ELISA test including its principle, procedure, and limitations.
Explain the various modes of HIV transmission and prevention methods.
Compare benign and malignant tumors in terms of growth, spread, and prognosis.
Explain metastasis including the process and factors that promote it.
Describe the three types of carcinogens with examples and their mechanisms.
Explain the role of oncogenic viruses in cancer development with examples.
Describe the various diagnostic methods for cancer including their advantages.
Explain chemotherapy including its mechanism, drugs used, and side effects.
Describe immunotherapy in cancer treatment including biological response modifiers.
Explain allergy as an immune disorder including causes and types.
Describe the mechanism of allergic reactions including cells and mediators involved.
Explain the role of mast cells and basophils in allergic reactions.
Describe the treatment of allergic reactions including emergency management.
Explain opioids including their source, mechanism of action, and effects.
Describe heroin including its preparation, effects, and dangers.
Explain cannabinoids including their source, mechanism of action, and effects.
Describe cocaine including its source, mechanism of action, and effects.
Explain how opioids bind to receptors and their physiological effects.
Describe how cocaine affects dopamine transport and its consequences.
Explain the long-term effects of alcohol abuse on various body systems.
Describe withdrawal symptoms including their causes and management.
Compare chikungunya and dengue in terms of vectors, symptoms, and prevention.
Explain hemozoin including its formation, effects, and role in malaria symptoms.
Describe natural killer cells including their origin, function, and importance.
Explain memory cells including their formation, types, and role in immunity.
Describe how vaccination leads to immunological memory and protection.
Explain how colostrum provides passive immunity to newborns.
Compare natural and artificial passive immunity with examples.
Describe Western blot including its principle and use in AIDS diagnosis.
Explain oncogenes including their types and role in cancer development.
Describe the process of metastasis and factors that influence it.
Explain radiotherapy including its mechanism and precautions needed.
Describe alpha-interferon including its source and use in cancer treatment.
Explain asthma as an allergic condition including triggers and symptoms.
Describe the use of adrenaline in treating severe allergic reactions.
Explain LSD including its effects and dangers.
Describe barbiturates including their medical uses and abuse potential.
Explain the complete life cycle of Ascaris including infective stage.
Compare the mosquito vectors of malaria, dengue, and filariasis.
Explain droplet infection including diseases spread and prevention.
Describe plague including its types, transmission, and historical significance.
Explain ringworm including causative fungi, affected areas, and transmission.
Describe the clinical features of ringworm infection.
Explain the pathophysiology of filariasis including lymphatic involvement.
Describe chronic filariasis including complications and deformities.
Explain the complications of typhoid including intestinal perforation.
Describe cyanosis in pneumonia including its cause and significance.
Explain buboes including their formation, location, and significance in plague diagnosis.
Compare bubonic and pneumonic plague in terms of symptoms and transmission.
Describe the pathophysiology of typhoid fever including systemic effects.
Explain how amoebiasis is diagnosed through stool examination and other tests.
Describe splenomegaly in malaria including its causes and significance.
Explain the cyclical nature of fever in malaria including its timing.
Describe the joint involvement in chikungunya and its long-term effects.
Explain retro-orbital pain in dengue fever and its mechanism.
Describe how ascariasis leads to anemia and nutritional deficiency.
Explain the complications of heavy ascariasis including intestinal obstruction.
Describe the mechanism of intestinal blockage in ascariasis.
Explain elephantiasis including its pathophysiology and clinical features.
Describe the morphology of ringworm lesions and their progression.
Explain the predilection sites for ringworm infection and reasons.
Describe comprehensive typhoid prevention including vaccination and sanitation.
Explain integrated malaria prevention including vector control and personal protection.
Describe ringworm prevention including personal hygiene and environmental measures.
Explain bacterial disease prevention through vaccination programs.
Describe plague prevention including vector control and surveillance.
Explain the effectiveness of mosquito nets in malaria prevention.
Describe personal hygiene measures for preventing fungal infections.
Explain the role of sanitation in preventing waterborne diseases.
Describe the dual role of antimalarial drugs in treatment and prevention.
Explain the importance of safe drinking water in disease prevention with examples.

Answer Key

Section A: Multiple Choice Questions

c) Complete physical, mental, and social well-being
c) Antibodies
b) Common cold
c) Aedes aegypti mosquito
b) Typhoid
b) Pneumonia
c) Plague
b) Amoebiasis
d) Plasmodium falciparum
b) Plasmodium
c) Roundworm
b) Wuchereria bancrofti
c) Fungi
c) Present from birth
c) Neutrophils and macrophages
b) Virus-infected cells
b) Slow but long-lasting
c) Ready-made antibodies
b) B-cells
b) Graft rejection
b) B-cells
a) IgG
b) IgA
c) IgM
c) Allergic reactions
b) Antigens
b) RNA virus (retrovirus)
b) Helper T-cells
c) Reverse transcriptase
b) AIDS
c) Sexual contact
c) Metastasis
d) Remain confined to original location
b) Physical carcinogens
b) HPV
a) Cancer diagnosis
b) Hair loss
b) Biological response modifiers
b) Exaggerated immune response
c) Allergic reactions
c) Mast cells
c) Allergic reactions
c) Opium poppy
c) Smack
b) Cannabis sativa
c) Coca plant
b) Opioid receptors
a) Dopamine transport
b) Liver cirrhosis
b) Drug dependence
c) Aedes mosquito
b) Malaria
b) Innate immunity
a) Primary immune response
b) Active immunity
b) Passive immunity
b) Passive immunity
b) Confirmatory test for AIDS
b) Genes that cause cancer
b) Tumor spread
b) Treatment of cancer
c) Immunotherapy
c) Allergic reaction
c) Severe allergic reactions
c) Hallucinogen
b) Sedatives
a) Egg
c) Filariasis
c) Pneumonia
c) Flea bite
b) Ringworm
c) Ringworm
b) Filariasis
c) Filariasis
b) Typhoid
b) Lack of oxygen
c) Lymph nodes
c) Lungs
b) Typhoid
c) Amoebiasis
d) All of the above
b) Malaria
c) Chikungunya
b) Dengue
b) Ascariasis
d) All of the above
b) Ascariasis
c) Filariasis
b) Ringworm
b) Ringworm
b) Typhoid
b) Malaria
c) Ringworm
d) All of the above
c) Plague
b) Malaria
b) Ringworm
b) Typhoid
c) Both a and b
b) Typhoid

Section B: Short Answer Questions (1 Mark Each)

World Health Organization.
A pathogen is a disease-causing organism.
Rhinovirus.
Aedes aegypti mosquito.
Widal test.
Streptococcus pneumoniae or Haemophilus influenzae.
Yersinia pestis.
Entamoeba histolytica.
Malaria caused by Plasmodium falciparum.
Sporozoite.
Ascaris lumbricoides.
Wuchereria bancrofti or Wuchereria malayi.
Microsporum, Epidermophyton, Trichophyton.
Innate immunity is the non-specific defense present from birth.
Neutrophils and macrophages.
Interferons are cytokine barriers that protect non-infected cells from viruses.
Active immunity is developed when the body produces its own antibodies after exposure to an antigen.
Passive immunity is when ready-made antibodies are transferred to an individual.
B-lymphocytes (B-cells).
Cell-mediated immunity is responsible for graft rejection.
Immunoglobulins (Ig).
IgG.
IgA is found in secretions like colostrum, tears, and saliva.
IgM.
IgE is involved in allergic reactions.
Vaccines contain weakened or inactivated pathogens or their antigens.
HIV is a retrovirus (RNA virus).
HIV primarily attacks helper T-lymphocytes.
Reverse transcriptase.
ELISA (Enzyme-Linked Immunosorbent Assay).
Sexual contact with an infected person.
Malignant tumors are characterized by metastasis (spreading to other parts of the body).
Benign tumors remain confined to their original location.
X-rays or UV rays.
Human Papillomavirus (HPV).
Biopsy is used for the diagnosis of cancer by examining a piece of tissue.
Hair loss or anemia.
Immunotherapy uses biological response modifiers like alpha-interferon.
Allergy is caused by an exaggerated immune response to allergens.
IgE antibody.
Mast cells and basophils.
Antihistamines are used to treat allergic reactions.
Opium poppy (Papaver somniferum).
Smack.
Cannabis sativa.
Coca plant (Erythroxylum coca).
Opioids bind to opioid receptors in the central nervous system.
Cocaine interferes with the transport of the neurotransmitter dopamine.
Long-term alcohol abuse causes liver cirrhosis.
Withdrawal symptoms occur when a person dependent on drugs or alcohol stops taking them.
Aedes mosquito.
Hemozoin is a toxic substance released when RBCs rupture in malaria, causing chills and fever.
Natural killer cells are part of innate immunity.
Memory cells are formed during the primary immune response.
Vaccination provides active acquired immunity.
Colostrum provides natural passive immunity.
Antivenom injection.
Western blot is used as a confirmatory test for AIDS.
Oncogenes are cancer-causing genes.
Metastasis refers to the spread of cancer cells from a primary tumor to other parts of the body.
Radiotherapy is used for the treatment of cancer.
Alpha-interferon is used in immunotherapy for cancer treatment.
Asthma is caused by an allergic reaction.
Adrenaline is used to treat severe allergic reactions (anaphylaxis).
LSD is a hallucinogen.
Barbiturates are sedatives or depressants.
The infective stage of Ascaris is the embryonated egg.
Culex mosquito.
Droplet infection is the transmission of pathogens through respiratory droplets from coughing or sneezing.
Plague is transmitted by flea bites from infected rodents.
Microsporum causes ringworm.
Intense itching is a primary symptom of ringworm.
The lymphatic system is affected in filariasis.
Genital organs and lower limbs may be affected in filariasis.
Intestinal perforation can occur in severe cases of typhoid.
It indicates a lack of oxygen (cyanosis).
Buboes are painfully swollen lymph nodes, characteristic of bubonic plague.
Pneumonic plague affects the lungs.
Sustained high fever, weakness, and stomach pain are symptoms of typhoid.
Stools with excess mucus and blood clots indicate amoebiasis.
An enlarged spleen (splenomegaly) is seen in malaria.
Recurring fever at regular intervals is characteristic of malaria.
Severe, often debilitating, joint pain is seen in chikungunya.
Pain behind the eyes is a characteristic symptom of dengue fever.
Muscular pain and internal bleeding are symptoms of ascariasis.
Malaria and ascariasis can cause anemia.
Blockage of the intestinal passage occurs in severe ascariasis.
Gross deformities of the lower limbs (elephantiasis) occur in filariasis.
Dry, scaly lesions are seen in ringworm.
Skin, nails, and scalp are affected in ringworm.
Typhoid is transmitted through contaminated food and water.
Mosquito control prevents malaria.
Maintaining personal hygiene prevents ringworm.
Vaccination prevents typhoid.
Rodent and flea control prevents plague.
Using mosquito nets prevents malaria at night.
Avoid sharing personal items like towels and clothes to prevent ringworm.
Proper sanitation prevents waterborne diseases like typhoid and amoebiasis.
Antimalarial drugs are used for both the treatment and prevention of malaria.
Safe drinking water prevents diseases like typhoid and amoebiasis.

Section C: Short Answer Questions (2 Marks Each)

According to WHO, health is a state of complete physical, mental, and social well-being, and not merely the absence of disease or infirmity. It emphasizes a holistic view of well-being beyond just physical fitness.
Four types of pathogens are:
- Bacteria: Salmonella typhi (causes typhoid)
- Viruses: Rhinovirus (causes common cold)
- Protozoa: Plasmodium vivax (causes malaria)
- Fungi: Microsporum (causes ringworm)
The common cold is caused by Rhinoviruses and transmitted through respiratory droplets or contaminated objects. Symptoms include nasal congestion, sore throat, cough, and fatigue.
Dengue fever is caused by the dengue virus (DENV) and is transmitted by the bite of an infected Aedes aegypti mosquito. It requires a mosquito vector to spread from person to person.
The Widal test is a serological test used to diagnose typhoid fever. It detects the presence of antibodies against the Salmonella typhi bacterium in the patient's serum.
Pneumonia is caused by bacteria like Streptococcus pneumoniae or Haemophilus influenzae. It leads to infection in the alveoli of the lungs, causing fever, chills, cough, and difficulty breathing.
Plague is caused by the bacterium Yersinia pestis. It is transmitted by flea bites from infected rodents or through respiratory droplets in its pneumonic form, causing fever, chills, and swollen lymph nodes (buboes).
Amoebiasis is caused by the protozoan Entamoeba histolytica. Symptoms include constipation, abdominal pain, and stools with excess mucus and blood clots.
The four species are P. vivax, P. malariae, P. ovale, and P. falciparum. Plasmodium falciparum causes the most severe form of malaria, known as malignant malaria.
Sporozoites are the infectious stage of the Plasmodium parasite. They are found in the salivary glands of infected female Anopheles mosquitoes and are injected into the human bloodstream during a mosquito bite.
Ascariasis is caused by the roundworm Ascaris lumbricoides. Symptoms include internal bleeding, muscular pain, fever, anemia, and potential blockage of the intestinal passage.
Filariasis (Elephantiasis) is caused by filarial worms like Wuchereria bancrofti. It results in chronic inflammation of the lymphatic vessels, especially of the lower limbs, leading to gross deformities.
Ringworm is caused by fungi like Microsporum, Epidermophyton, and Trichophyton. Its symptoms include the appearance of dry, scaly lesions on the skin, nails, and scalp, accompanied by intense itching.
Innate immunity is non-specific and present from birth, providing the first line of defense. Acquired immunity is pathogen-specific, develops after exposure to a pathogen, and is characterized by memory.
Physical barriers of innate immunity include the skin, which prevents the entry of microbes, and the mucus coating of respiratory and other tracts, which traps pathogens.
Interferons are proteins (a type of cytokine) secreted by virus-infected cells. Their function is to protect neighboring non-infected cells from further viral infection.
Active immunity is produced when the body makes its own antibodies after exposure to an antigen; it is slow but long-lasting. Passive immunity is when ready-made antibodies are given, providing fast but short-lived protection.
Natural Active Immunity: Develops after a natural infection (e.g., recovering from chickenpox). Artificial Active Immunity: Develops after vaccination (e.g., measles vaccine).
Humoral immunity is mediated by B-lymphocytes (B-cells). When activated, B-cells differentiate into plasma cells that produce antibodies to fight pathogens in body fluids (humors).
Cell-mediated immunity (CMI) is mediated by T-lymphocytes (T-cells). It is responsible for directly killing infected cells, activating other immune cells, and for graft rejection during organ transplants.
An antibody is a Y-shaped protein made of four polypeptide chains: two identical heavy (H) chains and two identical light (L) chains. The chains are linked by disulfide bonds, forming a variable region for antigen binding and a constant region.
The five types are:
- IgG: Most abundant, crosses the placenta.
- IgA: Found in secretions.
- IgM: First responder in primary infection.
- IgD: Activates B-cells.
- IgE: Involved in allergic reactions.
IgA is found in secretions like colostrum, saliva, tears, and mucus. Its function is to protect mucous membranes from pathogens.
IgE is involved in allergic reactions. It binds to mast cells and basophils, causing them to release histamine and other inflammatory chemicals upon encountering an allergen.
The principle of immunization is based on the immune system's 'memory'. A vaccine introduces antigens, stimulating a primary immune response and creating memory cells, which mount a rapid and strong secondary response upon actual infection.
Vaccines are preparations of weakened or killed pathogens, or their antigens. They stimulate the immune system to produce antibodies and memory cells without causing the disease, thus providing active immunity.
HIV (Human Immunodeficiency Virus) is a retrovirus. This means its genetic material is RNA, which it converts into DNA inside the host cell using an enzyme called reverse transcriptase.
HIV attacks helper T-cells because the virus's surface proteins can bind to the CD4 receptors present on these cells. This allows the virus to enter and replicate, eventually destroying the helper T-cells.
Reverse transcriptase is a viral enzyme that synthesizes DNA from an RNA template (reverse transcription). This allows the viral genetic information to be integrated into the host cell's DNA.
The ELISA (Enzyme-Linked Immunosorbent Assay) test is a widely used screening test to detect the presence of antibodies against HIV in a person's blood. A positive result is usually confirmed with a Western blot test.
Three modes of HIV transmission are:
- Unprotected sexual contact with an infected person.
- Sharing of infected needles among intravenous drug users.
- From an infected mother to her child through the placenta.
Benign tumors are non-cancerous, grow slowly, and remain localized. Malignant tumors are cancerous, grow rapidly, invade surrounding tissues, and can spread to other parts of the body (metastasis).
Metastasis is the property of malignant tumors where cancer cells break away from the primary tumor and travel through the blood or lymph to form new tumors in distant sites.
Three types of carcinogens are:
- Physical: Ionizing radiation like X-rays.
- Chemical: Tobacco smoke.
- Biological: Oncogenic viruses like HPV.
Human Papillomavirus (HPV) is associated with cervical cancer. Hepatitis B and C viruses are linked to liver cancer.
A biopsy is a medical procedure that involves taking a small sample of tissue for examination under a microscope. It is crucial for confirming a diagnosis of cancer and determining the type of cancer cells.
Chemotherapy is the use of cytotoxic drugs to kill rapidly dividing cancer cells. Common side effects include hair loss, anemia, and nausea because the drugs also affect normal rapidly dividing cells.
Immunotherapy is a cancer treatment that boosts the body's own immune system to fight cancer. It uses biological response modifiers like alpha-interferon to activate immune cells to recognize and destroy tumor cells.
An allergy is an exaggerated or hypersensitive response of the immune system to certain substances (allergens) present in the environment, such as pollen, dust, or certain foods.
In an allergic reaction, exposure to an allergen triggers the production of IgE antibodies. These antibodies attach to mast cells, which then release inflammatory chemicals like histamine, causing allergic symptoms.
Mast cells and basophils release histamine. They do so when an allergen binds to the IgE antibodies attached to their surface, a process called degranulation.
Allergic reactions are treated with drugs like antihistamines, which block the effect of histamine. In severe cases, steroids or adrenaline may be used to reduce inflammation and counter the reaction.
Morphine is a potent opioid analgesic derived from the latex of the opium poppy, Papaver somniferum. It is used medically for severe pain relief but is also a highly addictive drug of abuse.
Heroin, also known as smack, is a chemically modified form of morphine (diacetylmorphine). It is a powerful depressant that produces euphoria and is highly addictive.
Marijuana is a cannabinoid drug obtained from the inflorescences of the Cannabis sativa plant. It primarily affects the cardiovascular and central nervous systems.
Cocaine is a powerful stimulant obtained from the leaves of the coca plant, Erythroxylum coca. It produces a sense of euphoria and increased energy but is highly addictive and dangerous.
Opioids act by binding to specific opioid receptors located in the central nervous system and gastrointestinal tract. This binding action produces their analgesic (pain-killing) and euphoric effects.
Cocaine affects the nervous system by interfering with the reuptake of the neurotransmitter dopamine from the synaptic cleft. This leads to an accumulation of dopamine, causing overstimulation of the brain's pleasure and reward pathways.
Long-term alcohol abuse can lead to severe health problems, most notably liver cirrhosis (scarring of the liver). It can also cause damage to the nervous system, heart problems, and increases the risk of certain cancers.
Withdrawal symptoms are a set of physical and psychological effects that occur when a person who is physically dependent on a drug or alcohol suddenly stops or reduces their intake. They occur because the body has adapted to the presence of the substance.
Both chikungunya and dengue are transmitted by the bite of infected Aedes mosquitoes. While both cause fever and body aches, chikungunya is characterized by severe, often debilitating, joint pain.
Hemozoin is a toxic, insoluble pigment produced by the Plasmodium parasite as it digests hemoglobin in red blood cells. Its release into the bloodstream upon the rupture of RBCs is what triggers the characteristic cycles of fever and chills in malaria.
Natural killer (NK) cells are a type of cytotoxic lymphocyte and a major component of the innate immune system. They can recognize and kill tumor cells and virus-infected cells without prior sensitization.
Memory cells are long-lived B and T lymphocytes that are formed during the primary immune response to an antigen. They "remember" the antigen and allow for a much faster and stronger response upon subsequent exposure.
Vaccination introduces a safe form of an antigen into the body. This stimulates a primary immune response, leading to the formation of antibodies and long-lasting memory cells, which provide active, acquired immunity against future infections.
Colostrum, the first milk produced by a mother, is rich in antibodies, particularly IgA. When an infant drinks colostrum, these antibodies provide immediate, natural passive immunity, protecting the newborn from infections.
Two examples of passive immunity are:
- Natural: An infant receiving antibodies from its mother through the placenta or breast milk.
- Artificial: An injection of antivenom to a person bitten by a venomous snake.
The Western blot is a highly specific confirmatory test used to detect antibodies against HIV. It is typically performed after a positive screening result from an ELISA test to confirm the diagnosis of HIV infection.
Oncogenes are genes that have the potential to cause cancer. They are often mutated or overexpressed versions of normal genes called proto-oncogenes, which are involved in regulating cell growth and division.
Metastasis is the process by which cancer cells from a malignant tumor spread from the primary site to other parts of the body. The cells travel through the bloodstream or lymphatic system to establish secondary tumors.
Radiotherapy uses high-energy radiation, such as X-rays or gamma rays, to damage the DNA of cancer cells, leading to their death. The radiation is carefully targeted at the tumor to minimize damage to surrounding healthy tissue.
Alpha-interferon is a type of biological response modifier used in immunotherapy. It helps activate the immune system to fight cancer by enhancing the ability of immune cells like NK cells to recognize and attack tumor cells.
Asthma is a chronic inflammatory disease of the airways, often triggered by an allergic reaction to allergens like pollen or dust. This reaction causes the airways to swell, narrow, and produce excess mucus, leading to difficulty breathing, coughing, and wheezing.
Adrenaline (epinephrine) is used as an emergency treatment for severe allergic reactions (anaphylaxis). It works rapidly to constrict blood vessels, relax airway muscles to improve breathing, and reduce swelling.
LSD (Lysergic acid diethylamide) is a powerful synthetic hallucinogen. It drastically alters a person's perception, thoughts, and feelings, often causing vivid hallucinations and a distorted sense of time and reality.
Barbiturates are a class of drugs that act as central nervous system depressants, producing effects ranging from mild sedation to anesthesia. They are used medically as sedatives and anesthetics but have a high potential for abuse and addiction.
The Ascaris life cycle begins when a human ingests embryonated eggs from contaminated soil or food. The larvae hatch in the intestine, penetrate the intestinal wall, travel to the lungs via the bloodstream, and are then coughed up and swallowed to mature into adult worms in the small intestine.
Malaria is transmitted by the female Anopheles mosquito. Filariasis is transmitted by the female Culex mosquito. Dengue and chikungunya are transmitted by the Aedes mosquito.
Droplet infection is a mode of transmission where pathogens are spread through tiny droplets of mucus expelled from the mouth or nose of an infected person during coughing, sneezing, or talking. Diseases like the common cold and pneumonia spread this way.
Plague is primarily transmitted by the bite of fleas that have fed on infected rodents like rats. It causes high fever, chills, and in the bubonic form, painful swollen lymph nodes called buboes.
Fungi from the genera Microsporum, Epidermophyton, and Trichophyton cause ringworm. It spreads through direct contact with an infected person's skin or with contaminated objects like towels, combs, or clothes.
The symptoms of ringworm infection include the appearance of dry, scaly, ring-shaped lesions on the skin, nails, or scalp. These lesions are typically red and are accompanied by intense itching.
Filariasis primarily affects the lymphatic system. The filarial worms live in the lymphatic vessels, causing chronic inflammation and obstruction of lymph flow.
In chronic filariasis, the lymphatic vessels of the lower limbs are most commonly affected, leading to elephantiasis. The genital organs can also be affected, causing significant swelling and deformity.
A serious complication of severe typhoid fever is intestinal perforation. The infection can cause ulcers in the small intestine, which can rupture, leading to a life-threatening condition called peritonitis.
Cyanosis, a bluish or grayish discoloration of the skin, lips, and fingernails, indicates severe hypoxia (lack of oxygen) in the blood. In pneumonia patients, it is a sign that the lungs are failing to adequately oxygenate the blood.
Buboes are extremely painful, swollen lymph nodes, particularly in the groin, armpit, or neck. They are the hallmark sign of bubonic plague, caused by the accumulation of the Yersinia pestis bacteria in the lymph nodes.
Bubonic plague is transmitted by flea bites and affects the lymph nodes, causing buboes. Pneumonic plague is a more severe form that infects the lungs and can be spread from person to person through respiratory droplets.
Four key symptoms of typhoid fever are:
- Sustained high fever (39°C to 40°C)
- Weakness and fatigue
- Stomach pain and constipation
- Headache and loss of appetite
Amoebiasis can be diagnosed by a microscopic examination of a stool sample. The presence of Entamoeba histolytica trophozoites or cysts, along with excess mucus and blood clots in the stool, confirms the diagnosis.
During malaria, the spleen often becomes enlarged (splenomegaly) because it is working to remove the large number of infected and destroyed red blood cells from circulation. It can also become a site where parasites accumulate.
The recurring fever in malaria corresponds to the life cycle of the Plasmodium parasite. The fever spikes occur when a large number of infected red blood cells rupture simultaneously, releasing parasites and toxins (like hemozoin) into the bloodstream.
The characteristic symptoms of chikungunya are the abrupt onset of high fever and severe, often debilitating, pain in multiple joints. This joint pain can persist for weeks, months, or even years after the initial infection.
A characteristic symptom of dengue fever is severe pain behind the eyes, known as retro-orbital pain. This pain is often described as a deep, intense ache that worsens with eye movement.
Ascaris worms in the intestine compete with the host for nutrients, leading to malnutrition and anemia, especially in children with heavy infections. The worms can also cause minor internal bleeding from the intestinal wall.
Heavy Ascaris infections can lead to serious complications. A large mass of worms can physically block the intestinal passage, requiring surgical intervention. The worms can also migrate to and block the bile or pancreatic ducts.
In cases of heavy infection, a large number of adult Ascaris worms can form a tangled mass within the small intestine. This bolus of worms can physically obstruct the gut, causing severe abdominal pain, vomiting, and constipation.
Chronic filariasis leads to a condition called elephantiasis. Due to the blockage of lymphatic vessels, lymph fluid accumulates in the tissues, causing massive swelling and thickening of the skin and underlying tissues, most commonly in the legs and genitals.
The lesions seen in ringworm are typically circular or ring-shaped with a raised, scaly border and a clearer central area. These lesions can be dry or moist and are intensely itchy.
Ringworm commonly affects areas of the body that are warm and moist, such as the skin (especially in skin folds), scalp, groin (jock itch), and feet (athlete's foot). It can also infect the nails.
Typhoid can be prevented by ensuring access to safe drinking water, proper sanitation and sewage disposal, and maintaining good personal hygiene, especially handwashing. Vaccination is also available and recommended in high-risk areas.
Four methods of malaria prevention are:
- Using insecticide-treated mosquito nets (ITNs).
- Applying insect repellent to exposed skin.
- Eliminating mosquito breeding sites (stagnant water).
- Taking prophylactic antimalarial drugs when traveling to endemic areas.
Ringworm can be prevented by practicing good personal hygiene, such as keeping the skin clean and dry. It is also important to avoid sharing personal items like towels, clothing, combs, and sports equipment.
Vaccines are available for several bacterial diseases, including pneumonia (Streptococcus pneumoniae vaccine), typhoid (typhoid vaccine), and plague (plague vaccine for high-risk individuals). These vaccines help the body build active immunity.
Plague can be prevented by controlling rodent populations (e.g., rats) and their fleas in and around homes and workplaces. In areas where plague is present, it is important to avoid contact with sick or dead animals.
Mosquito nets, especially those treated with insecticide (ITNs), are highly effective because they create a physical barrier against mosquitoes during the night. This is when the Anopheles mosquitoes that transmit malaria are most active and likely to bite.
Personal hygiene measures to prevent ringworm include regular showering, keeping the skin clean and dry (especially in folds), wearing clean clothes, and not sharing personal items like towels or razors.
Proper sanitation, including the safe disposal of human waste, is crucial for preventing diseases that spread through the fecal-oral route. It prevents the contamination of food and water sources with pathogens like Salmonella typhi (typhoid) and Entamoeba histolytica (amoebiasis).
Antimalarial drugs have a dual role. They are used to treat active malaria infections by killing the parasites in the body. They are also used for prophylaxis (prevention) by travelers to endemic areas to prevent the infection from establishing itself if they are bitten by an infected mosquito.
Safe drinking water is vital for health as it prevents the transmission of numerous waterborne diseases. Pathogens like Salmonella typhi (typhoid), Vibrio cholerae (cholera), and Entamoeba histolytica (amoebiasis) are spread through water contaminated with feces.

Section D: Long Answer Questions (3 Marks Each)

WHO defines health as "a state of complete physical, mental, and social well-being and not merely the absence of disease or infirmity." This definition is significant because it moves beyond a purely biomedical model. It highlights that true health is multidimensional, involving not just a physically functional body, but also a positive state of mind, emotional resilience, and the ability to form and maintain healthy social relationships. A person free from any diagnosable illness might still be considered unhealthy if they suffer from chronic stress, depression, or social isolation.
Pathogens are disease-causing organisms classified into five main categories:
- Bacteria: Unicellular prokaryotes. Examples: Salmonella typhi (causes typhoid), Streptococcus pneumoniae (causes pneumonia).
- Viruses: Non-cellular infectious agents that replicate inside host cells. Examples: Rhinovirus (causes common cold), Human Immunodeficiency Virus (HIV).
- Protozoa: Unicellular eukaryotes. Examples: Plasmodium (causes malaria), Entamoeba histolytica (causes amoebiasis).
- Helminths: Parasitic worms. Examples: Ascaris lumbricoides (roundworm), Wuchereria bancrofti (filarial worm).
- Fungi: Eukaryotic organisms. Examples: Microsporum, Trichophyton (cause ringworm).
The common cold is an infectious disease of the upper respiratory tract caused primarily by Rhinoviruses. It is transmitted through respiratory droplets released when an infected person coughs or sneezes, or by touching contaminated surfaces. Symptoms include nasal congestion and discharge, sore throat, cough, headache, and fatigue, typically lasting 3-7 days. Prevention involves frequent hand washing and avoiding close contact with infected individuals.
Dengue fever is a viral disease caused by the dengue virus (DENV), which is transmitted by the bite of an infected female Aedes aegypti mosquito. Symptoms include high fever, severe headache, pain behind the eyes, muscle and joint pains, and a characteristic skin rash. Prevention focuses on mosquito control, such as eliminating stagnant water where mosquitoes breed, using repellents, and wearing protective clothing.
The Widal test is a serological agglutination test used for the diagnosis of typhoid (enteric) fever. Its principle is that antibodies produced by a patient infected with Salmonella typhi will react and agglutinate (clump) with specific antigens from the bacterium in a lab setting. A rising titer of these antibodies in paired serum samples taken over time provides a strong indication of an active infection.
Pneumonia is an infection that inflames the air sacs (alveoli) in one or both lungs, which may fill with fluid. It is most commonly caused by bacteria like Streptococcus pneumoniae and Haemophilus influenzae. It is transmitted through inhaling respiratory droplets from an infected person. Symptoms include fever, chills, cough with phlegm, and difficulty breathing. In severe cases, lips and nails may turn bluish due to lack of oxygen. Prevention includes vaccination and maintaining good hygiene.
Plague is a serious infectious disease caused by the bacterium Yersinia pestis. It is primarily transmitted through the bite of fleas from infected rodents (bubonic plague) but can also spread through respiratory droplets from an infected person (pneumonic plague). Symptoms include fever, weakness, and painful, swollen lymph nodes called buboes. Prevention involves rodent control, flea control, and vaccination for high-risk individuals.
Amoebiasis, or amoebic dysentery, is an intestinal infection caused by the protozoan parasite Entamoeba histolytica. It is transmitted through the fecal-oral route, by ingesting food or water contaminated with the parasite's cysts. Symptoms include abdominal pain, cramps, constipation, and stools containing excess mucus and blood clots. Prevention relies on proper sanitation, safe drinking water, and good personal hygiene.
The four species of Plasmodium that cause human malaria are P. vivax, P. malariae, P. ovale, and P. falciparum. P. falciparum is the most dangerous because it causes malignant malaria. This form is associated with higher levels of parasitemia (more parasites in the blood), and it can lead to severe complications like cerebral malaria, severe anemia, and organ failure, resulting in a higher mortality rate than the other forms.
Sporozoites are the motile, infective stage of the Plasmodium parasite. They develop in the mosquito's gut after it ingests gametocytes from an infected human's blood. The sporozoites then migrate to the mosquito's salivary glands. When the infected mosquito bites another human, it injects these sporozoites into the bloodstream, initiating the malaria infection in the new host.
Ascariasis is an infection of the small intestine caused by the roundworm Ascaris lumbricoides. It is transmitted by ingesting embryonated eggs from soil, food, or water contaminated with human feces. Symptoms of heavy infection include abdominal pain, malnutrition, anemia, and sometimes a physical blockage of the intestinal passage by a mass of worms. Prevention is based on proper sanitation and hygiene.
Filariasis is a parasitic disease caused by thread-like filarial worms, primarily Wuchereria bancrofti and W. malayi. It is transmitted by the bite of infected mosquitoes (Culex). The worms live in the human lymphatic system, causing chronic inflammation and obstruction, which over many years can lead to the massive swelling and deformity known as elephantiasis, typically in the legs and genitals. Prevention focuses on mosquito control.
Ringworm is a common fungal infection of the skin, scalp, or nails, and is not caused by a worm. The causative fungi belong to the genera Microsporum, Epidermophyton, and Trichophyton. It is transmitted through direct contact with an infected person or contaminated objects. Symptoms include itchy, red, scaly, ring-shaped patches on the skin. Prevention involves good personal hygiene and avoiding the sharing of personal items.
Innate immunity is the body's inborn, non-specific defense system, acting as the first line of defense against all pathogens (e.g., skin, phagocytic cells). Acquired immunity, in contrast, is pathogen-specific and develops over a lifetime. It is characterized by immunological memory, where the immune system "remembers" a pathogen after an initial encounter, leading to a stronger response upon subsequent exposures (e.g., immunity from vaccination or prior infection).
The four types of barriers in innate immunity are:
- Physical Barriers: Skin and mucous membranes that physically block pathogens from entering the body.
- Physiological Barriers: Factors like stomach acid, saliva, and tears that create a chemical environment hostile to microbes.
- Cellular Barriers: Phagocytic cells like neutrophils and macrophages, and Natural Killer (NK) cells that engulf and destroy pathogens.
- Cytokine Barriers: Proteins like interferons secreted by virus-infected cells that signal other cells to resist viral infection.
Interferons are a group of signaling proteins (cytokines) made and released by host cells in response to the presence of viruses. When a cell is infected by a virus, it produces interferons, which then travel to neighboring, uninfected cells. These interferons induce a state of antiviral resistance in the neighboring cells, making it harder for the virus to replicate and spread.
Active immunity involves the body's own immune system producing antibodies and memory cells in response to an antigen (e.g., through infection or vaccination). It is slow to develop but provides long-lasting protection. Passive immunity is acquired by receiving pre-formed antibodies from another source (e.g., from mother to fetus or via an injection of antivenom). It provides immediate but temporary protection as the body does not produce its own memory cells.
The four types of acquired immunity are:
- Natural Active: Immunity developed after recovering from a natural infection (e.g., measles).
- Artificial Active: Immunity induced by a vaccine (e.g., polio vaccine).
- Natural Passive: Immunity transferred from mother to baby via the placenta (IgG) or colostrum (IgA).
- Artificial Passive: Immunity conferred by injecting ready-made antibodies (e.g., anti-tetanus serum).
Humoral immunity, also known as antibody-mediated immunity, is a component of the adaptive immune system. It is primarily mediated by B-lymphocytes (B-cells). Upon activation by an antigen, B-cells differentiate into plasma cells, which secrete large quantities of antibodies into the blood and lymph. These antibodies neutralize or eliminate extracellular pathogens and toxins.
Cell-mediated immunity (CMI) is an immune response that does not involve antibodies. It is primarily driven by T-lymphocytes (T-cells) and involves the activation of phagocytes, antigen-specific cytotoxic T-lymphocytes, and the release of various cytokines in response to an antigen. CMI is most effective in destroying virus-infected cells, intracellular bacteria, and is the primary cause of transplant rejection.
An antibody, or immunoglobulin (Ig), is a large, Y-shaped protein. It is composed of four polypeptide chains: two identical large heavy (H) chains and two identical smaller light (L) chains, linked by disulfide bonds. Each arm of the 'Y' contains a variable region that forms a specific antigen-binding site, and a constant region that determines the antibody's class and function.
The five types of immunoglobulins (antibodies) are:
- IgG: Most abundant in blood, crosses the placenta to protect the fetus.
- IgA: Found in secretions (saliva, tears, milk), protects mucosal surfaces.
- IgM: The first antibody produced during an initial infection, effective at activating complement.
- IgD: Found on the surface of B-cells, acts as an antigen receptor.
- IgE: Involved in allergic reactions and defense against parasitic worms.
IgA is the main antibody found in mucosal secretions, including mucus, tears, saliva, and colostrum (the first breast milk). Its primary role is to provide localized protection on mucosal surfaces, which are major entry points for pathogens. It does this by preventing microbes from adhering to and penetrating the epithelial lining of the respiratory, gastrointestinal, and urogenital tracts.
IgE is the antibody primarily responsible for mediating type I hypersensitivity reactions, commonly known as allergies. When a person is sensitized to an allergen, they produce IgE antibodies that bind to the surface of mast cells and basophils. Upon re-exposure, the allergen cross-links these IgE molecules, triggering the cells to release histamine and other inflammatory mediators, causing allergic symptoms. IgE also plays a role in defending against parasitic worm infections.
The principle of immunization, or vaccination, is based on the adaptive immune system's property of 'memory'. A vaccine introduces a harmless form of a pathogen's antigen into the body. This stimulates a primary immune response, leading to the production of antibodies and, crucially, long-lived memory B and T cells. If the body is later exposed to the actual pathogen, these memory cells mount a rapid and powerful secondary immune response, preventing the disease from developing.
Vaccines are biological preparations that provide active acquired immunity to a specific infectious disease. They typically contain an agent that resembles a disease-causing microorganism, often made from weakened or killed forms of the microbe, its toxins, or one of its surface proteins (antigens). By stimulating the body's immune system to recognize the agent as a threat and create a memory of it, vaccines enable a faster and more effective response to future infections.
HIV (Human Immunodeficiency Virus) is a retrovirus. Its structure consists of an envelope with glycoproteins, a capsid, and a core containing its genetic material. Unlike most organisms that have DNA, HIV's genetic material is RNA. It is called a retrovirus because it uses a special enzyme, reverse transcriptase, to perform "reverse transcription," converting its RNA genome into DNA, which is then integrated into the host cell's genome.
HIV specifically targets helper T-cells (also known as CD4+ T-cells) because the gp120 protein on the virus's surface has a high affinity for the CD4 receptor molecule on these cells. This binding allows the virus to enter and infect the helper T-cells. The consequence is a progressive destruction of these cells, which are crucial for coordinating the immune response, leading to severe immunodeficiency (AIDS).
Reverse transcriptase is a crucial enzyme for HIV replication. After HIV enters a host cell, this enzyme reads the viral RNA genome and synthesizes a complementary DNA (cDNA) strand. This process is the reverse of normal transcription (DNA to RNA). The resulting viral DNA can then be integrated into the host cell's own DNA, effectively hijacking the cell's machinery to produce new virus particles.
The ELISA (Enzyme-Linked Immunosorbent Assay) test is a common laboratory method used to detect the presence of antibodies or antigens in a sample. For HIV diagnosis, it is used as a screening test to detect antibodies produced by the body in response to HIV infection. The principle involves using antigens fixed to a surface to capture the specific antibodies, which are then detected by a secondary antibody linked to an enzyme that produces a measurable color change.
The three primary modes of HIV transmission are:
- Sexual Contact: Unprotected vaginal, anal, or oral sex with an infected person.
- Blood-borne: Sharing contaminated needles among intravenous drug users, or transfusion of contaminated blood or blood products.
- Perinatal (Mother to Child): An infected mother can transmit the virus to her baby during pregnancy, childbirth, or breastfeeding. Prevention involves safe sex practices, not sharing needles, and screening blood donations.
Benign and malignant tumors differ significantly. Benign tumors are non-cancerous; they grow slowly, are typically encapsulated, and do not invade surrounding tissues or spread to other parts of the body (metastasize). Malignant tumors are cancerous; they are characterized by rapid, uncontrolled growth, invasion of nearby tissues, and the ability to metastasize, forming secondary tumors in distant organs, which makes them life-threatening.
Metastasis is the defining characteristic of malignant cancer. It is the process by which cancer cells break away from the primary tumor and enter the bloodstream or lymphatic system. These circulating tumor cells can then travel to distant sites in the body, exit the vessels, and establish new secondary tumors. The ability to metastasize is what makes cancer so difficult to treat once it has spread.
Carcinogens are agents that can cause cancer. They are categorized as:
- Physical Carcinogens: These include ionizing radiation like X-rays and gamma rays, and non-ionizing radiation like UV rays from the sun, which can damage DNA.
- Chemical Carcinogens: These include substances like asbestos, components of tobacco smoke (e.g., benzopyrene), and certain industrial dyes that can cause mutations in DNA.
- Biological Carcinogens: These are infectious agents, primarily oncogenic viruses like Human Papillomavirus (HPV), which can interfere with normal cell cycle control.
Oncogenic viruses are viruses that can cause cancer. A prominent example is the Human Papillomavirus (HPV), which is the primary cause of cervical cancer and is linked to several other cancers. The virus integrates its DNA into the host cell's genome and produces proteins that disrupt tumor suppressor genes like p53 and Rb, leading to uncontrolled cell proliferation. Another example is the Hepatitis B virus, which is a major cause of liver cancer.
The main diagnostic methods for cancer include:
- Biopsy and Histopathology: The definitive diagnosis, where a tissue sample is removed and examined under a microscope to identify cancer cells.
- Imaging: Techniques like X-rays, CT scans, and MRI are used to visualize internal tumors and assess their size and location.
- Blood Tests: Used to detect tumor markers or abnormal blood cell counts (for leukemias). These methods help not only to diagnose cancer but also to determine its stage and plan the most effective treatment.
Chemotherapy is a cancer treatment that uses powerful cytotoxic drugs to kill fast-growing cells in the body. Since cancer cells divide much more rapidly than most normal cells, they are more susceptible to these drugs. However, chemotherapy also affects normal fast-growing cells, such as those in hair follicles, bone marrow, and the digestive tract, leading to common side effects like hair loss, anemia, fatigue, and nausea.
Immunotherapy is a type of cancer treatment that harnesses the power of the patient's own immune system to fight the disease. One approach uses biological response modifiers, such as alpha-interferon. These substances can enhance the immune response by activating immune cells like T-cells and NK cells, making them more effective at recognizing and destroying cancer cells.
An allergy is a hypersensitivity disorder of the immune system. It is an exaggerated response to substances, known as allergens, that are normally harmless to most people. Common allergens include pollen, dust mites, mold spores, pet dander, insect stings, and certain foods or medicines. The immune system mistakenly identifies these substances as threats and launches an inappropriate and excessive inflammatory response.
The mechanism of an allergic reaction begins with sensitization, where initial exposure to an allergen causes plasma cells to produce large amounts of IgE antibodies. These IgE molecules attach to the surface of mast cells. Upon subsequent exposure, the allergen binds to and cross-links the IgE on the mast cells, causing them to degranulate and release potent inflammatory chemicals like histamine, leading to allergy symptoms.
Mast cells and basophils are the primary cells involved in allergic reactions. Mast cells are found in connective tissues throughout the body, especially near blood vessels and in the skin and mucous membranes. When an allergen binds to IgE antibodies on their surface, they release granules packed with inflammatory mediators, most notably histamine, which causes vasodilation, increased vascular permeability, and smooth muscle contraction.
The treatment of allergic reactions aims to relieve symptoms and reduce inflammation. Mild allergies are commonly treated with antihistamines, which block the action of histamine. Decongestants and nasal corticosteroids are also used. For severe, life-threatening allergic reactions (anaphylaxis), an emergency injection of adrenaline (epinephrine) is required to rapidly reverse the effects on breathing and blood pressure.
Opioids are a class of drugs derived from, or chemically similar to, compounds found in the opium poppy (Papaver somniferum). They act by binding to opioid receptors in the brain, spinal cord, and other organs. This action blocks pain signals and produces feelings of pleasure and euphoria, making them effective painkillers (e.g., morphine) but also highly addictive.
Heroin, also known as smack or diacetylmorphine, is a semi-synthetic opioid made from morphine. It is a powerful central nervous system depressant that produces intense euphoria. It is typically injected, snorted, or smoked and is one of the most addictive and dangerous drugs of abuse due to its high potential for overdose and the severe withdrawal symptoms it causes.
Cannabinoids are a class of chemical compounds that act on cannabinoid receptors in the body. The most well-known source is the Cannabis sativa plant, from which products like marijuana, hashish, and charas are derived. These drugs affect the cardiovascular system and brain function, leading to altered perceptions, mood changes, and impaired memory and coordination.
Cocaine is a powerful and addictive stimulant drug obtained from the leaves of the coca plant (Erythroxylum coca). It acts by blocking the reuptake of the neurotransmitter dopamine in the brain, leading to a buildup of dopamine and intense feelings of energy, alertness, and euphoria. Excessive use can cause paranoia, hallucinations, and severe cardiovascular complications.
Opioids exert their effects by binding to specific protein targets called opioid receptors, which are found on nerve cells in the brain, spinal cord, and gastrointestinal tract. When an opioid binds to these receptors, it inhibits the transmission of pain signals, resulting in analgesia. It also activates the brain's reward system, leading to feelings of pleasure and euphoria, which drives their addictive potential.
Cocaine's primary mechanism of action is the blockade of the dopamine transporter protein in the brain. This transporter is responsible for removing dopamine from the synapse after it has been released. By blocking this reuptake process, cocaine causes dopamine levels to increase dramatically, leading to overstimulation of postsynaptic neurons and the intense euphoric and stimulant effects associated with the drug.
Long-term, chronic alcohol abuse has devastating effects on multiple body systems. It is a leading cause of liver disease, progressing from fatty liver to alcoholic hepatitis and finally to irreversible cirrhosis. It also leads to damage to the central and peripheral nervous systems, cardiovascular problems like hypertension and cardiomyopathy, pancreatitis, and an increased risk of various cancers.
Withdrawal symptoms are a group of physical and psychological symptoms that occur upon the abrupt discontinuation or decrease in intake of substances like alcohol or drugs, to which the body has become dependent. They arise because the body has adapted its neurochemistry to the constant presence of the drug and is thrown into a state of hyper-excitability when the substance is removed. Symptoms can range from anxiety and tremors to seizures and delirium tremens in severe alcohol withdrawal.
Both chikungunya and dengue are viral diseases transmitted by the same vector: the Aedes mosquito, particularly Aedes aegypti. While they share symptoms like high fever, headache, and rash, the defining feature of chikungunya is extremely severe and often debilitating joint pain (arthralgia). Dengue is more commonly associated with severe headache, retro-orbital pain, and a risk of developing hemorrhagic fever. Prevention for both relies on mosquito control.
Hemozoin is a toxic, crystalline substance produced by the Plasmodium parasite inside red blood cells. The parasite digests the host's hemoglobin for nutrients, and the heme portion, which is toxic to the parasite, is polymerized into insoluble hemozoin crystals. When the infected red blood cell ruptures, hemozoin is released into the bloodstream, where it is recognized by the immune system and triggers a massive inflammatory response, causing the characteristic fever and chills of malaria.
Natural killer (NK) cells are a type of cytotoxic lymphocyte critical to the innate immune system. They originate from the bone marrow and circulate in the blood. Their primary function is to provide rapid responses to virus-infected cells and to detect and control early signs of cancer. Unlike T-cells, NK cells can recognize and kill these target cells without prior sensitization or activation by antigens.
Memory cells are a subset of T and B lymphocytes that are formed following a primary immune response to a pathogen. These cells are long-lived and "remember" the specific antigen they encountered. If the same pathogen enters the body again, these memory cells facilitate a much faster, stronger, and more effective secondary immune response, often preventing the disease from developing at all.
Vaccination works by exploiting the immune system's ability to create immunological memory. A vaccine introduces a safe version of a pathogen's antigens, prompting the body to mount a primary immune response. This process generates not only antibodies but also a pool of long-lived memory B and T cells specific to that pathogen. These memory cells provide long-term protection by ensuring a swift and powerful response to any future encounter with the live pathogen.
Colostrum, the first milk produced by a mother after birth, is a vital source of passive immunity for a newborn. It is extremely rich in ready-made antibodies, particularly secretory IgA. When the infant consumes colostrum, these antibodies coat the mucosal surfaces of their immature gastrointestinal tract, providing immediate protection against ingested pathogens until the infant's own immune system matures.
Natural passive immunity occurs without medical intervention, as when a fetus receives IgG antibodies from its mother across the placenta, or an infant receives IgA antibodies through breast milk. Artificial passive immunity is acquired through a medical procedure, such as receiving an injection of antibodies (immunoglobulins) to provide immediate, short-term protection against a specific threat, like an injection of anti-tetanus serum after a deep wound.
The Western blot is a highly specific analytical technique used to detect specific proteins in a sample. In AIDS diagnosis, it is used as a confirmatory test following a positive ELISA screen. It works by separating HIV proteins by size via gel electrophoresis, transferring them to a membrane, and then probing the membrane with the patient's serum. If antibodies specific to several different HIV proteins are present, they will bind, creating a characteristic pattern of bands that confirms the infection.
Oncogenes are genes that have the potential to cause cancer. They arise from the mutation of normal genes called proto-oncogenes, which are responsible for regulating cell growth and division. When a proto-oncogene is mutated or expressed at high levels, it can become a "turned-on" oncogene, leading to uncontrolled cell proliferation and the transformation of a normal cell into a cancer cell.
Metastasis is the complex, multi-step process by which cancer spreads from its primary site of origin to distant parts of the body. It involves cancer cells detaching from the main tumor, invading local tissues and blood or lymph vessels (intravasation), surviving in circulation, exiting the vessels at a new location (extravasation), and then proliferating to form a secondary tumor. Factors influencing this include cell motility, adhesion molecules, and the microenvironment of the target organ.
Radiotherapy, or radiation therapy, is a cancer treatment that uses high doses of radiation to kill cancer cells and shrink tumors. The radiation works by damaging the DNA of the cancer cells. Because cancer cells are typically dividing rapidly and have impaired DNA repair mechanisms, they are more vulnerable to this damage than healthy cells. Precautions are taken to precisely target the tumor and shield surrounding normal tissues as much as possible.
Alpha-interferon is a type of cytokine, a protein naturally produced by the body's immune cells. In cancer treatment, it is used as a form of immunotherapy, often for cancers like melanoma, Kaposi's sarcoma, and some leukemias. It is thought to work by both slowing the growth of cancer cells directly and by activating other parts of the immune system, such as NK cells and T-cells, to better attack and destroy the tumor.
Asthma is a chronic inflammatory condition of the airways, often with an allergic basis. When an asthmatic person is exposed to a trigger (like pollen, dust, or cold air), their immune system overreacts. This leads to inflammation, swelling, and constriction (bronchospasm) of the airway muscles, along with increased mucus production. This narrowing of the airways makes it difficult to breathe, causing the characteristic symptoms of wheezing, coughing, chest tightness, and shortness of breath.
Adrenaline (epinephrine) is the first-line emergency treatment for anaphylaxis, a severe, life-threatening allergic reaction. It works rapidly and powerfully to counteract the most dangerous symptoms of anaphylaxis. It constricts blood vessels to increase blood pressure, relaxes the muscles in the airways to relieve wheezing and improve breathing, and reduces swelling and hives. It is typically administered via an auto-injector.
LSD (Lysergic acid diethylamide) is one of the most potent hallucinogenic drugs. It profoundly alters perception, mood, and thought processes. Its effects are unpredictable and can include visual and auditory hallucinations, a distorted sense of time and identity, and intense emotional swings. The dangers of LSD include the potential for terrifying "bad trips," flashbacks, and engaging in risky behavior due to impaired judgment.
Barbiturates are a class of central nervous system depressant drugs. Medically, they have been used as sedatives, hypnotics (for sleep), and anesthetics. However, they have a high potential for abuse and physical dependence. They produce effects similar to alcohol, ranging from mild relaxation to slurred speech, impaired coordination, and unconsciousness at high doses. Overdose is extremely dangerous, especially when mixed with alcohol, as it can lead to respiratory arrest and death.
The life cycle of Ascaris lumbricoides begins when a human ingests its embryonated eggs via contaminated food or water. In the small intestine, larvae hatch, penetrate the intestinal wall, and enter the bloodstream. They travel to the lungs, mature further, and then ascend the respiratory tract to the pharynx, where they are coughed up and swallowed. Back in the small intestine, they develop into adult worms, mate, and produce eggs that are passed in the feces.
The mosquito vectors for these three diseases are distinct:
- Malaria: Transmitted by the female Anopheles mosquito, which typically bites at night.
- Dengue: Transmitted by the Aedes mosquito (primarily A. aegypti), which is a day-biting mosquito that breeds in clean, stagnant water near human dwellings.
- Filariasis: Transmitted by the female Culex mosquito, which often breeds in polluted water and also bites at night.
Droplet infection is a major mode of transmission for respiratory diseases. It occurs when an infected person coughs, sneezes, or talks, expelling tiny droplets containing pathogens into the air. A nearby person can then become infected by inhaling these droplets. Diseases that commonly spread this way include the common cold, influenza, and pneumonia. Prevention includes covering coughs and sneezes, hand hygiene, and maintaining distance from infected individuals.
Plague is a bacterial disease caused by Yersinia pestis. Its most common form, bubonic plague, is transmitted to humans through the bite of fleas that have previously fed on infected rodents, such as rats. A more virulent form, pneumonic plague, can be transmitted directly from person to person through respiratory droplets. Historically, plague has caused devastating pandemics, such as the "Black Death" in the 14th century.
Ringworm (tinea) is a fungal infection caused by dermatophytes from genera like Trichophyton and Microsporum. It commonly affects the skin, scalp, groin, and feet. The infection is highly contagious and spreads through direct skin-to-skin contact with an infected person or animal, or indirectly by touching contaminated objects like towels, combs, or locker room floors.
The clinical features of ringworm are quite characteristic. The infection typically presents as one or more itchy, red, circular lesions. These lesions often have a raised, scaly border and a clearer, less inflamed area in the center, creating a "ring-like" appearance. The affected skin may be dry and flaky, and in some cases, small blisters or pustules may form.
The pathophysiology of filariasis centers on the damage and obstruction of the lymphatic system. Adult filarial worms (Wuchereria bancrofti) reside in the lymphatic vessels and lymph nodes. Their presence, along with the host's inflammatory response to them, causes damage to the vessel walls, leading to lymphatic dysfunction, obstruction of lymph flow, and fluid accumulation in the surrounding tissues (lymphedema).
Chronic filariasis can lead to severe and disfiguring complications. The most well-known is elephantiasis, characterized by massive swelling and thickening of the skin, typically in the legs and scrotum. The genital organs can also be severely affected, leading to hydrocele (fluid accumulation in the scrotum). These conditions cause significant disability, social stigma, and are prone to secondary bacterial infections.
The most serious complication of typhoid fever is intestinal perforation. The Salmonella typhi bacteria can cause deep ulcers to form in the lymphoid tissue (Peyer's patches) of the small intestine. In severe, untreated cases, one of these ulcers can erode completely through the intestinal wall, spilling the gut contents into the abdominal cavity. This leads to peritonitis, a life-threatening medical emergency.
Cyanosis in a pneumonia patient is a very serious sign. It is a bluish or purplish discoloration of the skin and mucous membranes caused by a high concentration of deoxygenated hemoglobin in the blood. In pneumonia, it indicates that the lungs are so compromised by infection and fluid that they are failing to transfer enough oxygen into the bloodstream, a condition known as severe respiratory distress or failure.
Buboes are the classic sign of bubonic plague. They are extremely painful, swollen, and tense lymph nodes that develop near the site of the flea bite. The Yersinia pestis bacteria travel from the bite to the nearest lymph node, where they multiply rapidly, causing inflammation, hemorrhage, and necrosis, resulting in the characteristic bubo. Common locations are the groin, armpits, and neck.
Bubonic and pneumonic plague are two forms of the same disease. Bubonic plague is the most common form, resulting from a flea bite and characterized by buboes; it is not directly transmissible from person to person. Pneumonic plague is a more severe form where the infection spreads to the lungs. It is highly virulent and can be transmitted directly between people through inhaling infectious respiratory droplets.
The pathophysiology of typhoid fever involves the ingestion of S. typhi, which then invades the intestinal lining and multiplies within macrophages. The bacteria spread systemically through the bloodstream to the liver, spleen, and bone marrow. The release of endotoxins from the bacteria is thought to cause the characteristic sustained high fever, headache, abdominal pain, and systemic symptoms. The involvement of intestinal lymphoid tissue (Peyer's patches) can lead to ulceration and constipation or diarrhea.
Amoebiasis is diagnosed definitively by identifying the Entamoeba histolytica parasite in a stool sample. Under a microscope, a technician looks for either the motile, feeding trophozoite stage (which may contain ingested red blood cells) or the dormant cyst stage. The presence of blood and mucus in the stool is also a strong indicator. Other tests, like antigen detection in stool or serology to detect antibodies in the blood, can also be used.
Splenomegaly, or an enlarged spleen, is a common clinical finding in malaria. The spleen's primary roles include filtering blood and mounting immune responses. During a malaria infection, the spleen works overtime to clear the vast number of infected and damaged red blood cells from circulation. This intense activity, along with the accumulation of parasites and immune cells, causes the spleen to become significantly enlarged and palpable.
The cyclical fever pattern in malaria is synchronized with the life cycle of the Plasmodium parasite in the bloodstream. The parasites invade and multiply asexually within red blood cells. After a certain period (e.g., 48 hours for P. vivax), all the infected cells rupture at roughly the same time, releasing a new generation of parasites and a flood of toxins like hemozoin. This massive release triggers a strong inflammatory response from the host, causing the characteristic spike in fever and chills.
The joint involvement in chikungunya is its most prominent and debilitating feature. The disease causes severe polyarthralgia (pain in multiple joints), often affecting the small joints of the hands, wrists, ankles, and feet symmetrically. The pain is often accompanied by swelling and stiffness. In a significant number of patients, this crippling joint pain can persist for months or even years, leading to chronic arthritis.
Retro-orbital pain, or pain located deep behind the eyes, is a hallmark symptom of dengue fever. The exact mechanism is not fully understood but is believed to be related to the inflammation of tissues and muscles surrounding the eye, including the extraocular muscles. The pain is typically a constant, dull ache that is often exacerbated by eye movements.
Ascariasis can lead to anemia and nutritional deficiency, particularly in children with heavy worm burdens. The adult worms reside in the small intestine and consume a portion of the host's ingested nutrients, contributing to malnutrition. They can also cause chronic, low-grade blood loss from the intestinal lining, which, over time, can lead to iron-deficiency anemia.
A heavy infection with Ascaris can lead to severe and life-threatening complications. The most common is intestinal obstruction, where a large bolus of tangled worms physically blocks the gut, requiring emergency surgery. The worms can also migrate from the intestine into other organs, causing blockage of the bile duct (leading to jaundice) or the pancreatic duct (leading to pancreatitis).
Intestinal blockage in ascariasis occurs when a very large number of adult worms accumulate in the small intestine. These worms, which can be up to 35 cm long, can become entangled and form a large, writhing mass. This bolus of worms can completely obstruct the lumen of the intestine, preventing the passage of food and fluids and creating a surgical emergency.
Elephantiasis is the late-stage clinical manifestation of chronic lymphatic filariasis. It is caused by the long-term obstruction of lymphatic vessels by filarial worms and the resulting chronic inflammation. This blockage prevents the proper drainage of lymph fluid, leading to lymphedema (fluid accumulation) and subsequent massive swelling, thickening, and hardening of the skin and subcutaneous tissues, most commonly affecting the legs and genitals.
The lesions of ringworm (tinea) are typically well-demarcated, circular or oval patches. The classic lesion has an active, advancing border that is raised, red, and scaly, sometimes with small pustules. The central area of the lesion tends to heal and become less inflamed, which creates the characteristic "ring" appearance. The lesions are almost always intensely itchy.
Ringworm infections have a predilection for warm, moist, keratinized tissues. Therefore, common sites include the skin folds of the groin (tinea cruris or "jock itch"), the spaces between the toes (tinea pedis or "athlete's foot"), the scalp (tinea capitis), and the nails (tinea unguium). The fungi thrive in these environments where moisture can accumulate.
A comprehensive approach to typhoid prevention includes several key strategies. The most important are ensuring access to safe, treated drinking water and maintaining proper sanitation systems to prevent fecal contamination of water and food. Promoting good personal hygiene, especially handwashing with soap, is critical. Additionally, safe and effective typhoid vaccines are available and recommended for people living in or traveling to endemic areas.
Integrated malaria prevention involves a multi-pronged attack on the parasite and its vector. Key strategies include:
- Vector Control: Using insecticide-treated mosquito nets (ITNs) and indoor residual spraying (IRS) to kill mosquitoes.
- Personal Protection: Using mosquito repellents and wearing protective clothing.
- Environmental Management: Eliminating stagnant water sources where mosquitoes breed.
- Chemoprophylaxis: Taking antimalarial drugs to prevent infection when traveling to high-risk zones.
Preventing ringworm relies heavily on personal and environmental hygiene. Personal measures include keeping the skin clean and dry, especially in skin folds, and avoiding sharing personal items like towels, combs, clothing, and razors. Environmental measures involve regularly cleaning and disinfecting communal areas like showers, locker rooms, and sports mats where the fungi can thrive.
Vaccination is a cornerstone of preventing many serious bacterial diseases. For example, the Hib and PCV vaccines protect against Haemophilus influenzae and Streptococcus pneumoniae, major causes of pneumonia and meningitis. The DTaP vaccine protects against diphtheria, tetanus, and pertussis. Typhoid vaccines protect against Salmonella typhi. These programs have dramatically reduced the incidence of these diseases worldwide.
Plague prevention focuses on breaking the transmission cycle between rodents, fleas, and humans. This involves effective rodent control (e.g., eliminating food sources and shelter for rats) and flea control in and around human settlements. In endemic areas, people should avoid handling sick or dead animals. A vaccine exists but is typically reserved for high-risk individuals like laboratory workers.
Mosquito nets, particularly those treated with a long-lasting insecticide (ITNs), are highly effective in malaria prevention because they target the biting behavior of the Anopheles mosquito. These mosquitoes are most active and bite between dusk and dawn. Sleeping under a net creates a physical barrier, and the insecticide kills or repels mosquitoes that come into contact with it, protecting the individual and reducing the local mosquito population.
Good personal hygiene is key to preventing fungal infections like ringworm. This includes daily washing with soap and water, followed by thoroughly drying the skin, especially between the toes and in skin folds. It is also important to wear clean, dry clothing, change socks and underwear daily, and avoid sharing personal items like towels, shoes, or sports gear that can harbor and transmit fungi.
Proper sanitation, which involves the safe containment, treatment, and disposal of human feces, is fundamental to public health. It prevents the contamination of drinking water sources, soil, and food with pathogens that are transmitted via the fecal-oral route. This directly prevents a wide range of waterborne diseases, including typhoid, cholera, amoebiasis, and various diarrheal illnesses.
Antimalarial drugs play a crucial dual role. For treatment, drugs like artemisinin-based combination therapies (ACTs) are used to kill the Plasmodium parasites in the blood of an infected person, curing the disease. For prevention (prophylaxis), individuals traveling to malaria-endemic regions can take these drugs to kill any parasites that may enter their bloodstream from a mosquito bite, thus preventing the infection from ever taking hold.
Access to safe drinking water is one of the most important pillars of public health because it prevents the transmission of a vast number of infectious diseases. Water contaminated with human or animal feces can carry pathogens like Salmonella typhi (typhoid), Vibrio cholerae (cholera), Entamoeba histolytica (amoebiasis), Giardia, and various viruses. Ensuring water is properly treated and protected from contamination breaks this major transmission route and saves millions of lives.

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