If twelve new cases of a disease were reported during January and 4000 people were at risk, what is the incidence rate?

To determine the incidence rate, you need to calculate the number of new cases of the disease relative to the population at risk during a specific time period, which in this case is January. The formula commonly used to calculate the incidence rate is:

Incidence Rate = (Number of New Cases / Population at Risk) x 1000

In this scenario, there were 12 new cases reported, and 4,000 individuals were at risk. Plugging in these values:

Incidence Rate = (12 / 4000) x 1000

= 0.003 x 1000

= 3 per 1000

This result indicates that the incidence rate of the disease is 3 new cases per 1,000 people at risk during that month. This measurement is critical in public health as it helps gauge the frequency of new cases in relation to the population size, allowing for better understanding and resource allocation in disease prevention and control.

The other options relate to either prevalence, which measures existing cases rather than new cases, or provide incorrect incidence calculations. Thus, the calculation establishing an incidence rate of 3 per 1000 accurately reflects the local increase in disease cases within the defined population at risk.