Introduction The categorization of female commercial sex work according socio-anthropologic criteria constitutes a pre-requisite to assess differential risks of HIV exposure.

Methods A cross-sectional questionnaire survey was conducted to describe the spectrum of commercial sex work in Bangui, the capital city of the Central African Republic, among 345 sexually active women having more than 2 sexual partners other than their regular partner during the last 3 months and reporting to have received money or “gifts” in return of their sexual relationships.

Results HIV infection in study female sex worker (FSW) population was strongly associated with anal sex practice with last clients (OR, 4.3), irregular condom use in last 3 months (OR, 24.9), and alcohol consumption before sex (adjusted OR, 2.8). Networks of commercial sex work comprised six different FSW categories, including two groups of “official” professional FSW primarily classified according to their site of work [i) “kata“ (18.6%) representing women working in poor neighbourhoods of Bangui; ii) “pupulenge” (13.9%) working in hotels and night clubs to seek White men] and four groups of “clandestine” nonprofessional FSW classified according to their reported main activity [i) “market and street vendors” (20.8%); ii) “schoolgirls or students“ (19.1%) involved in occasional transactional sex (during holydays); iii) “housewives or unemployed women” (15.7%); “civil servants” (11.9%) working as soldiers or in public sector]. HIV varied according to FSW categories. HIV prevalence was 6-fold higher among “kata” than “pupulenge” (39.1% versus 6.3%). “Students”, “civil servants” and “housewives” were the less HIV-infected (6.1%, 9.8%, 13.0%, respectively), whereas “sellers” constituted the category of highest HIV prevalence (31.9%).

Conclusion Our observations highlight the high level of vulnerability of both poor professional “kata” and nonprofessional “street vendors” FSW categories which should be particularly taken in account when designing prevention programs for STIs/HIV control purposes.