Scenario In Community X (population 20,000), an epidemiologist conducted a prevalence survey in January of 2012 and reported an HIV prevalence of 2.2%. Over the next 12 months, the department of health reported an additional 50 new HIV cases between February 2012 and January 2013. The total population stayed constant at 20,000. Part 1 How many people had HIV in January 2012? Present or describe the formula you used to arrive at your answer. Calculate the incidence rate assuming no HIV-related deaths over the 12-month period. Present or describe the formula you used to arrive at your answer. Be sure to clearly indicate the numerator and denominator used in your calculation and include an appropriate label for the rate.

Part I: We can use this formula to determine the number of people who had HIV January 2012.

HIV prevalence rate is x the number of HIV-positive people

By substituting the values given, you get:

HIV infected people = 2,2% x 20,000 HIV-infected people = 0,022 x 120,000 HIV-infected people = 440

In January 2012, there were 440 HIV-positive people.

Part 2: The formula below can be used to determine the incidence rate for HIV-related deaths within the 12-month period.

Incidence Rate = New HIV cases / Population at Risk x Time Period

The population was stable at 20,000, and no HIV-related deaths were reported. This means that the risk population for HIV remains constant over the 12-month period. If we substitute the values above, then:

The incidence rate is 50/20,000×12 months. Incidence rates = 50/240,000. Incidence rates = 0.0002083

So, HIV prevalence in Community X during the 12-month period was 0.0002083, which is 0.02083%/year.