In 2014, a study investigated the frequency of HIV in a remote New Zealand community a total of 132 people participated in the study. A serological tests to diagnose cases of early HIV were conducted for each participant during 2014. Two cases were identified. The researchers followed those at risk for another year, and during this time frame another person was diagnosed.
(a) What was the prevalence of HIV in 2014?
(b) What was the prevalence of HIV among study participants at the end of 2015 Assume no loss to follow-up.
(c) What was
the cumulative incidence
of HIV over the study period?
(d) It appeared that not all the people at risk were followed for the entire year (2015). In fact only 65 people were followed for 12 months, 5 participants were followed for 10 months, 22 were followed for 7 months, 8 were followed for 6 months, 15 for 4 months and another 15 for 2 months. Calculate
the person-time of observation
(e) What was the
incident rate
of HIV during 2015.
(f) Assuming HIV has no cure (which is not correct if detected early!) and the incidence rate of HIV in the community remained constant what should happen to the prevalence of HIV in this cohort over time?