Measuring trends in HIV testing and new HIV infections among female sex workers in Zimbabwe

Female sex workers in sub-Saharan Africa are at increased risk of HIV acquisition and have a higher burden of HIV than women in the wider population. Despite this there remain gaps in our understanding of new HIV infections. Strengthening empirical data on key HIV indicators could improve the provision of targeted and equitable treatment and prevention services. The aim of my PhD is to understand trends in HIV testing and new infections among female sex workers in Zimbabwe and explore methods for the analysis of routinely collected clinic data to measure HIV indicators and inform programme delivery. I conducted a systematic review exploring knowledge of HIV status and provided major contributions to a second review on HIV incidence, both among female sex workers in sub-Saharan Africa. In published literature, knowledge of HIV status ranged from 4% to 95.2% between 2002 and 2020, with wide heterogeneity in estimates and gaps in data unable to support the analysis of trends over time. Higher estimates were reported in East and Southern Africa, with a median knowledge of HIV status of 58.1% (IQR 38.1-73.1) compared to 41.0% (IQR 22.7-59.3) in West and Central Africa. Thirty two studies reported empirical estimates of HIV incidence between 1985 to 2020. Median incidence was 4.3 new HIV infections per 100py (IQR 2.8-7.0). Incidence among women who engage in sex work was nearly eight times higher than matched total population women (IRR 7·8, 95% CI 5.1-11.8). Both reviews demonstrated the wide variation in the definitions used for recruitment of female sex workers to studies, national gaps in data and the lack of longitudinal data or repeat measures in the same populations. The main focus of my PhD is Zimbabwe. I analysed routinely collected programme data and recent HIV infection testing results from a nationally scaled programme for female sex workers (the KP Programme) run by the Centre for Sexual Health and HIV/AIDS Research. Among 86,197 FSW accessing programme services over 254,653 clinic visits between 2009 and 2019, 54,503 HIV tests were recorded for 39,462 women. HIV test-positivity declined from 47.9% to 9.6% (aOR 6.08 95% CI 5.52-6.70), partly explained by an increase from 18.2% to 56.7% of tests being among women testing within 6 months of a previous test. I calculated an overall seroconversion rate of 3.8 per 100py (95% CI 3.4-4.2) among 6665 women with >1 HIV test at a clinic during this period, which showed a steady decline over calendar time after accounting for an increase in younger women accessing services and HIV testing frequency. I estimated a higher seroconversion rate of 5.6 per 100py (95% CI 4.8-6.5) among younger women, and higher rates for women within the first year of service access at 5.8 per 100py (95% CI 5.0-6.7). The implementation of a recent HIV infection testing algorithm in the KP Programme between 2021 and 2023 classified 11.7% (95%CI 10.0-13.5) of HIV-positive tests as newly acquired infections, and estimated an HIV incidence rate of 3.4 new HIV infections per 100py (95% CI 2.7-1.0). HIV test-positivity and seroconversion rates show encouraging declines over time among female sex workers attending a targeted programme in Zimbabwe. Despite these declines, rates of new HIV infections remain high, particularly among younger women and those recently accessing services, demonstrating the need for intensifying and better targeting of prevention programming. Routinely collected and individually linked HIV testing data from programmes targeting female sex workers can provide valuable insights into epidemic indicators to inform programming strategies and enhance existing approaches to HIV surveillance among female sex workers in sub-Saharan Africa.