This study aims to estimate the prevalence of HIV among each of the three key populations in Vietnam: people who inject drugs (PWID), female sex workers (FSW), and men who have sex with men (MSM) and quantify their shared risk factors for HIV infection through a systematic review and meta-analysis of recent literature (published in 2001–2017) in the relevant topics. A total of 17 studies consisting of 16,304 participants were selected in this review. The meta-analysis results revealed that the pooled prevalence estimates with 95% confidence intervals (CIs) among PWID, FSW, and MSM were: 0.293 (0.164, 0.421), 0.075 (0.060, 0.089), and 0.085 (0.044, 0.126), respectively. The findings also indicated that injecting drug use (OR: 9.88, 95%CI: 4.47–15.28), multiperson use of injecting equipment (OR: 2.91, 95%CI: 1.69, 4.17), and inconsistent condom use (OR: 2.11, 95%CI: 1.33, 2.90) were the shared risk factors for HIV infection among these population groups. The findings highlighted the importance of HIV prevention approaches to addressing the shared sexual and drug-related practices among the key populations in consideration of their overlapping social networks.

Establishing accurate population size estimates (PSE) is important for prioritising and planning provision of services. Multiple source capture−recapture sampling method increases PSE accuracy and reliability. In August 2018, the three-source capture−recapture (3S-CRC) method was employed with a stringent assumption of sample independence to estimate the number of female sex workers (FSW) in Rwanda. Using Rwanda 2017 FSW hotspots mapping data, street and venue-based FSW were sampled at the sector level of each province and tagged with two unique gifts. Each capture was completed within one week to minimise FSW migration between provinces and recall bias. The three captures had 1042, 1204 and 1488 FSW. There were 111 FSW recaptured between captures 1 and 2; 237 between captures 2 and 3; 203 between captures 1 and 3 and 46 captured in all three. The PSE for street and venue-based FSW in Rwanda lies within 95% credible set: 8328–22 806 with corresponding median of 13 716 FSW. The 3S-CRC technique was low-cost and relatively easy to use for PSE in hard-to-reach populations. This estimate provides the basis for determining the denominators to assess HIV programme performance towards FSW and epidemic control and warrants further PSE for home- and cyber-based FSW in Rwanda.

In 2009, we examined HIV and sexually transmitted infections (STIs) in 750 female sex workers (FSWs) in Shanghai using a cross-sectional survey. Participants (mean age 27 years) were interviewed and tested for HIV and selected STIs. Prevalence was: HIV 0·13%, chlamydia 14·7%, gonorrhoea 3·5% and syphilis 1·3%. In a demographic multivariate model, younger age, higher income and originating from provinces other than Zhejiang and Shanghai were independently associated with STI. In a social and sexual behavioural model, women working in small venues with fewer clients per week, use of drugs, and higher price charged per sex act indicated a greater risk for STI. Although HIV appears rare in Shanghai FSWs, chlamydial infection is common, especially in women aged <25 years (prevalence 19·6%). Since STI and HIV share similar risk factors, preventive intervention measures should be implemented immediately based on the venues and characteristics of FSWs to prevent future spread of HIV.