Population HIV Viremia and Epidemic Transition: Findings from Sequential Surveys in Six sub-Saharan African Countries

Abstract 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 two 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 HIV prevalence, the 95-95-95 cascade, population viral load suppression (PVLS), population viremia (PV), HIV incidence, and IPR using survey-weighted methods. PV 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 74.5% to 88.0% in Round 2; PV ranged from 2.4% to 8.3% and 1.0% to 4.7%, respectively. In Round 2, undiagnosed infection accounted for most PV in four countries (53.1%-71.4%). Incidence estimates were lower in Round 2 in five countries, but confidence intervals were wide and overlapping. IPR ranged from 3.0%-6.7% in Round 1 to 2.1%-5.1% in Round 2; estimates were <3% in Eswatini, Lesotho, and Malawi, but confidence intervals included 3%. Conclusions PVLS 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.