PopART is a community randomized trial that is investigating whether a community-wide combination HIV prevention package including annual home-based HIV testing, active referral and the offer of immediate ART for those testing HIV-positive, along with the promotion of proven HIV prevention methods (such as voluntary medical male circumcision, prevention of mother to child transmission and condom use), will help to prevent transmission and substantially reduce new HIV infections. The study is being conducted in 21 communities in Zambia and South Africa (randomized into 3 arms, each with 7 communities) with a total population of approximately 1.2 million individuals.

HIV Prevention Trials Network (HPTN) 071 (PopART) will investigate the impact on HIV incidence of universal voluntary HIV counseling and testing (with referral to care) provided to a community through a house-to-house campaign, in combination with early ART for individuals who are HIV-positive, and other proven preventive interventions. The design of HPTN 071 (PopART) will allow the study team to distinguish between the impact of universal testing with referral for HIV care in accordance with national guidelines, and the impact of universal testing with referral for early ART initiation for those with HIV infection. In addition, HPTN 071 (PopART) will determine if a program of universal voluntary testing, including early ART initiation, is feasible and acceptable when delivered on a large scale to entire communities. Evaluating the effectiveness of universal voluntary HIV counseling and testing with the offer of early ART is a key global health priority.

Inclusion Criteria:

1. Population Cohort

   1. 18 - 44 years of age
   2. Able and willing to provide informed consent
   3. Residing within catchment area of a designated local health unit and intending to remain so for the next three years
   4. Residing in a randomly selected household

2. Case-Control Study 1 Inclusion Criteria:

   1. At least 18 years of age
   2. Able and willing to provide informed consent
   3. Resident in the cluster during the first round of testing
   4. Visited by a CHiP team and offered testing during the first round of home-based testing

3. Case-Control Study 2 Inclusion Criteria:

   1. At least 18 years of age
   2. Able and willing to provide informed consent
   3. Resident in the cluster during the first round of testing
   4. Tested HIV-infected in CHiP home-based testing, or HIV-infected and disclosed that they were previously diagnosed as HIV-infected to CHiP team

4. Case-Control Study 3 Inclusion Criteria:

   1. At least 18 years of age
   2. Able and willing to provide informed consent
   3. Resident in the cluster during the second round of testing
   4. Visited by a CHiP team and offered testing during the second round of home-based testing

Exclusion Criteria:

1. Population Cohort Exclusion Criteria:

   1. Current or planned enrollment in another HIV treatment, prevention, or Pre-Exposure Prophylaxis (PrEP) study
   2. Current, planned or prior enrollment in an HIV vaccine study
   3. Anything that, in the opinion of the investigator, would preclude informed consent, make study participation unsafe, complicate interpretation of study outcome data, or otherwise interfere with achieving the study objectives.

2. Case-Control Study 1 Exclusion Criteria:

   1. Individuals belonging to the Population Cohort or other case-control studies
   2. Individuals known to be HIV-infected after testing elsewhere.

3. Case-Control Study 2 Exclusion Criteria:

   1. Individuals enrolled in the Population Cohort or other case-control studies
   2. HIV-infected individuals already on ART before study commences

4. Case-Control Study 3 Exclusion Criteria:

   1. Known HIV infected from CHiP data.
   2. Individuals belonging to the Population Cohort or other case-control studies