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 1: To determine how many people had HIV in January 2012, we can use the formula:

Number of people with HIV = HIV prevalence rate x Total population

Substituting the given values, we get:

Number of people with HIV = 2.2% x 20,000 Number of people with HIV = 0.022 x 20,000 Number of people with HIV = 440

Therefore, there were 440 people with HIV in January 2012.

Part 2: To calculate the incidence rate assuming no HIV-related deaths over the 12-month period, we can use the formula:

Incidence rate = Number of new cases of HIV / Population at risk x Time period

Since the population stayed constant at 20,000 and there were no HIV-related deaths reported, the population at risk remains the same for the entire 12-month period. Substituting the given values, we get:

Incidence rate = 50 / 20,000 x 12 months Incidence rate = 50 / 240,000 Incidence rate = 0.0002083

Therefore, the incidence rate of HIV in Community X over the 12-month period was 0.0002083 or 0.02083% per year.