Virus Quiz : Test your knowledge

1. Which of the following best describes a “viral genome segment”? (as in segmented viruses)

1. A portion of host DNA accidentally packaged into the virion.
2. A separate nucleic acid molecule that encodes part of the viral genetic information.
3. A protein fragment cleaved from the viral capsid.
4. A piece of RNA that cannot be replicated.

2. With reference to “herd immunity threshold” (HIT) for a viral disease, which of the following is correct?

1. HIT increases as the basic reproduction number (R₀) increases.
2. HIT is independent of the efficacy of the vaccine used.
3. HIT is always 50% of the population irrespective of the virus.
4. HIT is lower for viruses with higher R₀.

3. Which of the following statements about “oncoviruses” is/are correct?

1. They are viruses associated with the development of cancers in humans or animals.
2. All oncoviruses are retroviruses.
3. Some oncoviruses can be prevented by vaccination, thereby reducing cancer risk.

Select the correct answer using the code below:

1. 1 only
2. 1 and 2 only
3. 1 and 3 only
4. 1, 2 and 3

4. In many viral infections, “antigenic stability” is advantageous for vaccine design because:

1. It means the virus cannot infect more than one species.
2. It ensures that viral antigens do not change rapidly, so vaccines remain effective for longer periods.
3. It guarantees that the virus is non-pathogenic.
4. It implies that the virus cannot replicate in humans.

5. Which of the following is the most appropriate explanation for “super-spreader events” in viral epidemics?

1. Events where viruses replicate only inside laboratory cultures.
2. Situations in which a small number of infected individuals infect a disproportionately large number of secondary cases.
3. Events that only involve vector-borne transmission.
4. Incidents where the virus is transmitted solely by contaminated food.

6. With reference to “R_e” (effective reproduction number), which of the following statements is/are correct?

1. R_e takes into account the proportion of the population that is immune.
2. R_e may change over time as interventions are introduced.
3. If R_e is maintained below 1 for a sufficient period, the outbreak tends to decline.

Select the correct answer using the code below:

1. 1 and 2 only
2. 2 and 3 only
3. 1 and 3 only
4. 1, 2 and 3

7. In the context of virus–host interaction, “species barrier” refers to:

1. The physical barrier of skin that always prevents viral entry.
2. Genetic and biological differences that limit a virus’s ability to infect different species.
3. The legal restriction on movement of animals between countries.
4. The effect of antiviral drugs on viral replication.

8. In a vaccine trial against a viral disease, “vaccine efficacy” of 80% most appropriately means:

1. 80% of vaccinated individuals will never be infected in their lifetime.
2. There is an 80% reduction in disease among vaccinated people compared with unvaccinated people under trial conditions.
3. 80% of the virus is killed in laboratory culture by the vaccine.
4. 20% of vaccinated people will definitely get severe disease.

9. With reference to “mucosal immunity” in viral infections, which of the following is/are correct?

1. Secretory IgA plays a key role in protection at mucosal surfaces.
2. Mucosal immunity is especially important for viruses entering via respiratory or gastrointestinal tracts.
3. Systemic IgG antibodies are the only important component of mucosal defence.

Select the correct answer using the code below:

1. 1 only
2. 1 and 2 only
3. 2 and 3 only
4. 1, 2 and 3

10. For a virus predominantly spread by contaminated water, the most direct long-term public health intervention to interrupt transmission is:

1. Mass distribution of insecticide-treated nets.
2. Improvement of water supply, sanitation, and safe sewage disposal.
3. Exclusive focus on antiviral drug prophylaxis.
4. Restriction of all international air travel.