Question
A study published in 1990 (Amer. J. Pub. Health 80:pp209-10) investigated the occurrence of HIV infection among prisoners in Nevada. Of 1105 prison inmates who were tested for HIV upon admission to the prison system, 36 were found to be infected. All uninfected prisoners were followed for a total of 1207 person-years and retested for HIV upon release from prison. Two of the uninfected inmates demonstrated evidence of new HIV infection. Assuming that the 2 prisoners were infected during their time in prison:
a. Based on the above information, calculate the incidence rate of HIV infection among prisoners in the Nevada prisons.
b. Express the incidence rate calculated in part a in terms of cases per 1000 person-years.
c. Why can’t you obtain an estimate of risk based on the information provided?
d. Why would estimating risk likely be inappropriate for these data?
e. Calculate the prevalence of HIV infection among incoming prisoners in the Nevada prison under study.
Source:
