JMIR Publications

ABSTRACT

Background:

Limited data exist describing the sex worker population size in South Sudan

Objective:

A population size estimation exercise among female sex workers (FSW) in South Sudan was undertaken in Juba, the capital, and Nimule, on the South Sudan-Uganda boarder during the Eagle Survey to inform resource allocation and service provision for FSW.

Methods:

The Eagle Survey utilized the service and unique object multipliers and three-source capture-recapture methods to estimate the size of FSW population in Juba and Nimule in conjunction with a respondent-driven sampling (RDS) survey. For the service multiplier, the number of FSW testing for HIV in 2015 (for Juba) and 2016 (for Nimule) were obtained from the LINKAGES program targeting FSW. RDS survey participants were asked in a face-to-face interview whether they had been tested for HIV by LINKAGES during the relevant period. Two separate unique object distributions were conducted in Juba and Nimule. In Nimule these were combined to become a three-source capture-recapture. The exercise involved distribution of keychains and bangles as unique objects to FSW, record of number who received unique objects and questions during RDS eligibility screening to assess whether FSW received unique objects.

Results:

In Juba, the service multiplier method yielded an estimate of 5,800 (95% CI: 4,927-6,673) FSW. The unique object estimate (of keychain and RDS participation) yielded a similar result of 5,306 (95% CI: 4,673-5,939). Another estimate using RDS participation and receipt of a bangle yielded a much lower estimate of 1,863 (95% CI: 1,776-1,951) as did a two-source estimate of keychain and bangle 2,120, (95% CI: 2,028-2,211). A three-source capture-recapture estimate could not be produced because aggregate rather than individual level data were collected during the third capture. The multiplier estimate, the keychain and RDS participation estimates were taken as final estimates for Juba. In Nimule, the service multiplier method yielded an estimate of 9,384 (95% CI: 8,511-10,257). The two-source estimates for keychain and RDS yielded 6,973 (95% CI: 4,759-9,186); bangles and RDS yielded 13,104 (95% CI: 7,101-19,106) which were much higher estimates and keychains and bangles yielded lower estimates of 1,322 (95% CI: 1,223-1,420). The 3-source capture-recapture method using the Bayesian nonparametric latent-class model-based estimate yielded a population of 2,694 (95% CI: 1,689-6,945) and this was selected as final estimate for Nimule.

Conclusions:

The service and unique object multipliers and three-source capture-recapture method were successfully used to estimate the number of FSW in Nimule, while the service and unique object multiplier methods were successfully used in Juba. These methods yielded higher than previously estimated FSW population sizes. These estimates will help inform resource allocation and advocacy efforts to support services for FSW.