Application of the capture-recapture method for estimating number of mobile male sex workers in a port city of Bangladesh.

Male sex workers (MSWs) and sex trades are not new in Bangladesh. Current HIV interventions for MSWs need to be expanded in the major cities, but the number of MSWs needs to be scientifically estimated. Although two-sample capture-recapture surveys are suitable for closed populations, this method was here applied to indirectly estimate the number of mobile MSWs in a conservative social setting, a port city of Bangladesh. Use of the method resulted in an estimation of 248 MSWs (95% confidence interval, 246-250) who picked up clients only at open and known contact venues. This estimate does not, however, reflect the total number as MSWs who worked in unknown hidden venues and could not be reached. Experience suggests that the two-sample capture-recapture method is a simple technique for reliably estimating an unrecognized population. The limitation of this method can be minimized by shortening the time gap between surveys, creating an enabling environment to encounter harassment of MSWs, and offering safety to peer-staff.