Undetectable HIV-1 viral load among virally suppressed people living with HIV: implications for Undetectable equals Untransmittable (U=U) in resource-limited settings using dried spot testing.

The Undetectable=Untransmittable (U=U) campaign, grounded in strong scientific evidence, affirms that people living with HIV (PLHIV) with an undetectable viral load (VL), defined as ≤50 copies per milliliter (c/mL) or <200 c/mL of HIV RNA, do not transmit HIV to sexual partners. In resource-limited settings, VL is commonly measured using dried blood spot (DBS) testing, which has a higher limit of detection (550-1000 c/mL). We report the proportion of PLHIV with VL <1000 c/mL who also had VL <200 c/mL and ≤50 c/mL to inform interpretation of DBS VL results under U=U. We analyzed data from 13 cross-sectional nationally representative surveys (2015-2019), including PLHIV aged 15-59 years receiving antiretroviral therapy (ART) with valid plasma VL results. We estimated the proportion of participants with VL <200 c/mL and ≤50 c/mL among those with VL <1000 c/mL, overall and among those on ART ≥12 months using survey weights. Among 16,533 PLHIV across 13 countries, 87.3% had VL <1000 c/mL. For PLHIV with VL <1000 c/mL, 95.4% had VL <200 c/mL and 84.9% had VL ≤50 c/mL. Among those on ART ≥12 months, 96.6% had VL <200 c/mL, and 87.4% had VL ≤50 c/ml. Most PLHIV with VL <1000 c/mL had a VL <200 c/mL and ≤50 c/mL, indicating no risk of sexual HIV transmission. Our findings provide evidence that in settings relying on DBS VL testing, most PLHIV with VL <1000 c/mL likely fall below 200 c/mL or are undetectable based on the assay's lower limit of detection.