Short Answer Questions (50)

1. 1. What is a disease? Give a brief definition.
   A disease is any condition that impairs normal structure or function of the body, producing specific signs and symptoms. It reduces the ability of the organism to perform normal activities.
2. 2. Differentiate between infectious and non-infectious diseases.
   Infectious diseases are caused by pathogens and can spread between individuals (e.g., influenza), while non-infectious diseases are not contagious and include genetic, nutritional or lifestyle disorders (e.g., diabetes).
3. 3. List the major types of disease-causing agents (pathogens).
   Pathogens include bacteria, viruses, fungi, protozoa and helminths (parasitic worms). Each has distinct structures and modes of causing disease.
4. 4. What are bacteria? Mention one structural feature.
   Bacteria are single-celled prokaryotes lacking membrane-bound nucleus. They often have a cell wall and reproduce by binary fission.
5. 5. Name two bacterial diseases and their causative organisms.
   Examples: Tuberculosis caused by Mycobacterium tuberculosis; cholera caused by Vibrio cholerae.
6. 6. What is a virus? How does it differ from a bacterium?
   Viruses are acellular particles composed of nucleic acid and protein coat and require host cells to reproduce. Unlike bacteria, they have no cellular structure and cannot be cultured on ordinary media.
7. 7. Give two examples of viral diseases.
   Common examples: Influenza (flu) and polio. Other viral diseases include common cold, dengue and measles.
8. 8. What are fungi? Give one example of a fungal infection.
   Fungi are eukaryotic organisms that can be unicellular or multicellular. Fungal infections include ringworm and athlete's foot caused by dermatophytes.
9. 9. Explain protozoa with one disease example.
   Protozoa are single-celled eukaryotes; some are parasitic. Malaria is caused by protozoa of the genus Plasmodium, transmitted by mosquitoes.
10. 10. What are helminths? Provide one example.
    Helminths are parasitic worms, often intestinal, such as roundworms and tapeworms. Example: Ascaris lumbricoides (roundworm) causes intestinal infection.
11. 11. How can infectious diseases spread through contaminated water and food?
    Pathogens in contaminated water or food are ingested and infect the gastrointestinal tract, causing diseases like cholera, typhoid and food poisoning.
12. 12. What is airborne transmission? Give an example.
    Airborne transmission occurs when pathogens travel in droplets expelled by coughing or sneezing; inhalation by others leads to infection — e.g., influenza and tuberculosis.
13. 13. Define vector and give an example of a vector-borne disease.
    A vector is a living carrier (often insect) that transmits pathogens between hosts. Example: Anopheles mosquitoes transmit malaria.
14. 14. What is direct contact transmission?
    Direct contact transmission involves physical contact with an infected person or their body fluids, spreading diseases like scabies or some respiratory infections.
15. 15. Explain the terms 'symptom' and 'sign' with examples.
    A symptom is subjective (felt by patient) like pain; a sign is objective and observable, like fever or rash measured by others.
16. 16. What is a carrier in epidemiology?
    A carrier harbours a pathogen without showing symptoms and can transmit it to others; carriers play roles in disease spread (e.g., Typhoid Mary historical example).
17. 17. How is diagnosis of infectious diseases generally made?
    Diagnosis combines patient history, clinical signs and symptoms with laboratory tests such as blood tests, cultures, microscopy, or molecular tests like PCR.
18. 18. What is the role of laboratory culture in diagnosing bacterial infections?
    Culturing allows growth of bacteria on selective media for identification and antibiotic sensitivity testing, guiding targeted treatment.
19. 19. Describe one mechanical barrier of the body that prevents infection.
    The skin acts as a barrier preventing entry of pathogens; mucous membranes trap microbes, and cilia in the respiratory tract help remove them.
20. 20. What are phagocytes and their function?
    Phagocytes (e.g., macrophages, neutrophils) are immune cells that engulf and digest invading microbes as part of innate immunity.
21. 21. Differentiate innate and adaptive immunity briefly.
    Innate immunity is immediate and non-specific (barriers, phagocytes), while adaptive immunity is specific, slower to develop but has memory via B and T lymphocytes.
22. 22. What is an antibody?
    An antibody is a protein produced by B-cells that recognises a specific antigen and helps neutralise or mark pathogens for destruction.
23. 23. Explain vaccination in simple terms.
    Vaccination introduces a safe form of a pathogen or its components to stimulate the immune system to develop memory cells without causing disease, providing future protection.
24. 24. What is herd immunity and why is it important?
    Herd immunity occurs when a high proportion of a population is immune (via vaccination or past infection), reducing overall disease spread and protecting vulnerable individuals.
25. 25. Why are antibiotics ineffective against viruses?
    Antibiotics target bacterial structures/processes (e.g., cell walls) that viruses lack; viruses replicate inside host cells using host machinery.
26. 26. Define antibiotic resistance and one way it develops.
    Antibiotic resistance is when bacteria evolve to survive antibiotic exposure, often due to misuse like incomplete courses or over-prescription, allowing resistant strains to persist.
27. 27. Give two measures to prevent foodborne diseases.
    Cook food thoroughly, store it at safe temperatures, maintain kitchen hygiene and use clean water to avoid contamination.
28. 28. How does handwashing reduce disease transmission?
    Handwashing with soap removes pathogens from hands, preventing transfer to food, eyes, mouth or other people and lowering infection risk.
29. 29. What is the significance of sanitation in public health?
    Sanitation (safe waste disposal and clean water) prevents waterborne diseases, improves community health and reduces outbreaks of infections like cholera.
30. 30. Describe the basic life cycle step for malaria parasite relevant to prevention.
    Malaria parasites alternate between human hosts and mosquito vectors; preventing mosquito bites (nets, repellents) interrupts transmission and reduces cases.
31. 31. What is an epidemic? How does it differ from a pandemic?
    An epidemic is a sudden rise in disease cases in a community; a pandemic is an epidemic that spreads across countries/continents affecting a large population.
32. 32. Name one zoonotic disease and its animal reservoir.
    Rabies is zoonotic; reservoirs include dogs and other mammals that can transmit the virus to humans via bites.
33. 33. Explain the role of vaccination programmes in disease control.
    Vaccination programmes immunise large populations, reduce disease incidence, prevent outbreaks and in some cases lead to eradication (e.g., smallpox).
34. 34. What does DOTS stand for and which disease is it associated with?
    DOTS: Directly Observed Treatment, Short-course — a supervised multi-drug treatment strategy used for tuberculosis control.
35. 35. How are viral infections managed clinically if antibiotics are ineffective?
    Viral infections are managed with supportive care (rest, fluids, symptom relief), antivirals where available, and prevention via vaccination and hygiene.
36. 36. Give two examples of personal hygiene practices that lower infection risk.
    Regular handwashing, bathing, safe food handling, and covering mouth when coughing reduce the spread of pathogens.
37. 37. What is a disinfectant? Give one example.
    A disinfectant is a chemical used to kill or inactivate pathogens on surfaces; example: sodium hypochlorite (bleach) solution.
38. 38. Describe briefly how respiratory infections can be reduced in schools.
    Promote cough etiquette, ensure hand hygiene, keep classrooms ventilated, and encourage sick students to stay home to limit transmission.
39. 39. What is passive immunity? Provide an example.
    Passive immunity is temporary protection from preformed antibodies; example: maternal antibodies transferred to the fetus through placenta or via breast milk.
40. 40. How does the body create memory against a pathogen?
    During adaptive immune response, B and T cells form memory cells after initial exposure, enabling faster and stronger responses upon re-exposure.
41. 41. Why is completing an antibiotic course important?
    Completing the prescribed course ensures elimination of susceptible bacteria and reduces the chance of resistant strains surviving and proliferating.
42. 42. What role do public awareness campaigns play in disease prevention?
    They educate communities about hygiene, vaccination, vector control and early treatment-seeking, which improves prevention and response to outbreaks.
43. 43. Give one reason why accurate diagnosis is crucial before prescribing antibiotics.
    Accurate diagnosis distinguishes bacterial from viral infections, preventing unnecessary antibiotic use and reducing resistance development.
44. 44. What is the importance of safe drinking water in disease control?
    Safe drinking water prevents waterborne diseases like cholera and diarrhoea, thereby reducing morbidity and mortality in communities.
45. 45. How can vector breeding sites be controlled in communities?
    Remove stagnant water, clean containers, use larvicides where necessary and promote community clean-up to reduce mosquito breeding.
46. 46. Mention one global success achieved through vaccination.
    Smallpox eradication worldwide through coordinated vaccination campaigns is a major public health success.
47. 47. What is the role of nutrition in disease resistance?
    Good nutrition supports immune function; deficiencies (e.g., vitamin A, protein) weaken immunity and increase susceptibility to infections.
48. 48. Why is isolation used in infection control?
    Isolation separates infected individuals to prevent transmission to healthy people, reducing spread during outbreaks.
49. 49. How are emerging infectious diseases monitored?
    Through surveillance systems, reporting networks, laboratory confirmation and epidemiological investigations to detect and respond early to outbreaks.
50. 50. Suggest a concise exam-ready answer for 'How can disease spread be prevented?'
    Prevention includes hygiene (handwashing), safe water and food, sanitation, vaccination, vector control, prudent antibiotic use and public health education to reduce transmission.

This set of 50 Short Answer Questions is aligned with NCERT Class 9 — Chapter 14: Why Do We Fall Ill? Use these for revision, classroom practice, and CBSE exam preparation.