Question

Virulence of a disease is indicated by

• A. . Proportional mortality rate
• B. . Morbidity rate
• C. . Case fatality ratio
• D. . Specific morality rate

Hint:

Remember:
- Morbidity: Sickness/disease occurrence.
- Mortality: Death occurrence.
- Virulence: Severity/deadliness (best measured by CFR - what proportion of sick people die).
- Incidence: New cases.
- Prevalence: Existing cases.

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The question asks for the epidemiological measure that best indicates the virulence of a disease. Virulence refers to the severity of a disease or its ability to cause severe disease or death.

Step 3: Detailed Explanation:
* Case Fatality Ratio (CFR): CFR is the proportion of individuals diagnosed with a disease who die from that disease, within a specified period. It is calculated as:
\[ \text{CFR} = \frac{\text{Number of deaths from a specific disease}}{\text{Number of confirmed cases of that disease}} \times 100 \]
A high CFR indicates that the disease is very severe and likely to cause death among those infected, thus directly reflecting its virulence.
* Proportional mortality rate: This is the proportion of all deaths that are due to a specific disease or cause. It tells about the relative importance of a cause of death but not necessarily its severity among those infected.
* Morbidity rate: This refers to the rate of disease in a population (e.g., incidence or prevalence). It indicates how often a disease occurs or exists but not its severity or deadliness.
* Specific mortality rate: This is a mortality rate calculated for a specific subgroup (e.g., age-specific mortality rate) or for a specific disease. While it indicates deaths, CFR is more directly a measure of severity among cases.
Therefore, the case fatality ratio is the best indicator of a disease's virulence.

Step 4: Final Answer:
Virulence of a disease is indicated by Case fatality ratio.

Answer 2

Virulence describes how severe or deadly a disease is for the people who actually catch it, so the right measure has to compare deaths specifically against the number of people who got the disease, not the whole population.

1. Proportional mortality rate: This compares deaths from one disease to all deaths from every cause, which tells us how big a killer a disease is compared to others, but not how deadly it is among people who actually catch it.
2. Morbidity rate: This measures how often a disease occurs in a population, showing how widespread it is, not how severe or deadly it is once someone is infected.
3. Case fatality ratio: This is calculated as deaths from a disease divided by the number of confirmed cases of that disease. Because it directly compares deaths to the people who were actually sick, it captures exactly how severe or deadly the disease is for those affected, which is what virulence means.
4. Specific morality rate: This measures deaths from a cause within a defined subgroup of the whole population, such as an age group, rather than comparing deaths only among the people who caught the disease.

Since only the case fatality ratio measures deaths against the number of people who actually got the disease, it is the measure that reflects virulence.

Therefore, the correct answer is Case fatality ratio.