How many people had HIV in January 2012? Present or describe the formula you used to arrive at your answer.

The formula for prevalence rate is as follows:

Prevalence rate = (Number of cases of a disease in a population ÷ Total population in that area) × 1000

Therefore, we would need to obtain the number of cases of HIV in the population and the total population in the area in question to calculate the prevalence rate and the number of people who had HIV in January 2012.