The study will be a multi-site prospective observational cohort of males and females who are vulnerable to HIV and other STIs. Step 1 of the study is the evaluation of participants without HIV with quarterly follow up visits up to 72 weeks. At each follow up visit, we will administer behavioral questionnaires, HIV testing, STI testing, and other laboratory testing per the schedule of evaluations. Participants will also perform home-based HIV testing between study visits per the schedule of evaluations. Step 2 is the incident HIV acquisition evaluation. Follow-up visits will be conducted every four weeks up to 12 weeks after initial HIV diagnosis and then quarterly up to 48 weeks. Individuals will be monitored for HIV disease outcomes, STIs, and surveys, and other lab collections will be administered per the schedule of evaluations. Participants who are virally-suppressed at the completion of Step 2 will transition to Step 3 for long-term follow-up semi-annually out to week 192. Evaluation will primarily be HIV monitoring, surveys for consideration of trial participation, and specimen storage per the schedule of evaluations.
Multinational Observational Cohort of HIV and other Infections (MOCHI). This observational study is to gain information regarding the number of new HIV infections among people who engage in behaviors that make them vulnerable to acquiring HIV across multiple international sites.