Introduction: Acute HIV infection (AHI) is the brief period between viral acquisition and the appearance of HIV antibodies and cannot be detected by routinely used HIV rapid diagnostic tests (RDTs). Its role is likely to become increasingly important in the rapidly changing context of HIV testing in high-burden countries. We describe the characteristics of individuals attending HIV testing services (HTS) in rural Eswatini and the prevalence of newly diagnosed HIV, including AHI.

Methods: Adults aged ≥18 years were enrolled at six routine HTS between June 2022 and April 2023. Participants completed detailed questionnaires. Routine HIV testing was conducted using the national serial RDT algorithm (Determine and Uni-Gold). HIV viral load (VL) analysis was performed on the Xpert platform (Xpert HIV-1 Viral Load, Cepheid) in the central laboratory. Newly diagnosed HIV was defined as a positive HIV RDT algorithm with detectable VL (established HIV), or negative or discordant HIV RDT together with VL ≥10 000 copies/mL (AHI).

Results: Of 1095 participants with a median age of 27 years (IQR 22-33), 684 (61.5%) were women. Risk factors for HIV acquisition were common: >1 sexual partner (332, 30.3%), condomless sex (452, 44.5%), not knowing main partner's HIV status (437, 42.8%). Symptoms consistent with AHI (713, 65.1%) and genito-urinary (660, 60.3%) infections were common. Overall, 41 participants (3.7%, 95% CI 2.7% to 5.0%) were diagnosed with HIV; 31 (2.8%, 95% CI 1.9% to 3.9%) with established HIV and 10 (0.9%, 95% CI 0.04% to 1.7%) with AHI, representing 24.4% (95% CI 12.4% to 40.3%) of new diagnoses. All participants diagnosed with AHI reported symptoms consistent with AHI.

Conclusions: Our study among a general adult population attending HTS revealed a high overall HIV prevalence with a substantial proportion of AHI, highlighting the decreasing sensitivity of routine HTS to detect all HIV infections. To address AHI, accurate and accessible diagnostic tools and AHI testing guidance are needed.