Population HIV Viremia and Epidemic Transition: Findings From Sequential Surveys in 6 Sub-Saharan African Countries.

Background: Testing and treatment targets may not fully capture the progress of the epidemic. Whether cascade gains translate into short-term reductions in new infections, as reflected by the incidence-to-prevalence ratio (IPR), remains uncertain. Methods: We analyzed 2 rounds of Population-based HIV Impact Assessment surveys in Eswatini, Lesotho, Malawi, Tanzania, Uganda, and Zimbabwe (Round 1, 2015-2017; Round 2, 2019-2023) among adults aged 15-59 years. We estimated human immunodeficiency virus (HIV) prevalence, the 95-95-95 cascade, population viral load suppression (PVLS), population viremia (PV), HIV incidence, and IPR using survey-weighted methods. Population viremia was categorized as undiagnosed and viremic, diagnosed but not on antiretroviral therapy (ART), or on ART but not suppressed. Results: The sample included 113 970 Round 1 and 112 445 Round 2 participants. Across countries, PVLS ranged from 52.0% to 72.4% in Round 1 and from 74.5% to 88.0% in Round 2; PV ranged from 2.4% to 8.3% in Round 1 and from 1.0% to 4.7% in Round 2. In Round 2, undiagnosed infection accounted for most PV in 4 countries (53.1%-71.4%). Incidence estimates were lower in Round 2 in 5 countries, but CIs were wide and overlapping. The incidence-to-prevalence ratio ranged from 3.0% to 6.7% in Round 1 and from 2.1% to 5.1% in Round 2; estimates were <3% in Eswatini, Lesotho, and Malawi, but CIs included 3%. Conclusions: Population viral load suppression increased, and PV declined in all countries, but precision for short-term IPR change was limited. Residual viremia was concentrated among undiagnosed adults, supporting targeted testing, rapid linkage, and treatment continuity.