Measles epidemic can be anticipated when propoion of susceptible children in a community reaches –
**Core Concept**
In epidemiology, the proportion of susceptible individuals in a population that can lead to an outbreak or epidemic is a critical concept. The herd immunity threshold is a key concept here, which determines the proportion of individuals that need to be immune to prevent the spread of a disease.
**Why the Correct Answer is Right**
The correct answer is related to the concept of herd immunity threshold, which is typically around 93-95% for measles. When the proportion of susceptible children in a community reaches this threshold, an outbreak or epidemic can be anticipated. This is because a small number of susceptible individuals can become infected and spread the disease to others, leading to a rapid increase in cases. The measles virus has a basic reproduction number (R0) of around 12-18, which means that a single infected individual can infect up to 12-18 others in a fully susceptible population.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is likely incorrect because the herd immunity threshold for measles is generally higher than 50%. While 50% susceptibility may lead to some cases, it is unlikely to result in an epidemic.
* **Option B:** This option is likely incorrect because the herd immunity threshold for measles is generally lower than 90%. While 90% susceptibility may lead to some cases, it is unlikely to result in an epidemic.
* **Option C:** This option is likely incorrect because the herd immunity threshold for measles is generally higher than 95%. While 95% susceptibility may lead to some cases, it is unlikely to result in an epidemic.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that the herd immunity threshold is not a fixed value and can vary depending on the disease, population, and other factors. Additionally, achieving herd immunity requires a high level of vaccination coverage, which is often challenging in areas with limited access to healthcare.
**Correct Answer: C. 95%**