Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2020 Sep 1;85(1):30-38.
doi: 10.1097/QAI.0000000000002393.

Estimating the Population Size of Female Sex Workers in Zimbabwe: Comparison of Estimates Obtained Using Different Methods in Twenty Sites and Development of a National-Level Estimate

Elizabeth Fearon  1 , Sungai T Chabata  2 , Sitholubuhle Magutshwa  2 , Tendayi Ndori-Mharadze  2 , Sithembile Musemburi  2 , Henry Chidawanyika  3 , Absolom Masendeke  3 , Sue Napierala  4 , Elizabeth Gonese  5 , Amy Herman Roloff  5 , Beth A Tippett Barr  5 , Peter H Kilmarx  5 , Ramona Wong-Gruenwald  6 , Samson Chidiya  7 , Mutsa Mhangara  7 , Dagmar Hanisch  8 , Jessie K Edwards  9 , Brian Rice  10 , Isaac Taramusi  11 , Tendai Mbengeranwa  11 , Portia Manangazira  12 , Owen Mugurungi  12 , James R Hargreaves  10 , Frances M Cowan  2   13
Affiliations

Estimating the Population Size of Female Sex Workers in Zimbabwe: Comparison of Estimates Obtained Using Different Methods in Twenty Sites and Development of a National-Level Estimate

Elizabeth Fearon et al. J Acquir Immune Defic Syndr. .

Abstract

Background: National-level population size estimates (PSEs) for hidden populations are required for HIV programming and modelling. Various estimation methods are available at the site-level, but it remains unclear which are optimal and how best to obtain national-level estimates.

Setting: Zimbabwe.

Methods: Using 2015-2017 data from respondent-driven sampling (RDS) surveys among female sex workers (FSW) aged 18+ years, mappings, and program records, we calculated PSEs for each of the 20 sites across Zimbabwe, using up to 3 methods per site (service and unique object multipliers, census, and capture-recapture). We compared estimates from different methods, and calculated site medians. We estimated prevalence of sex work at each site using census data available on the number of 15-49-year-old women, generated a list of all "hotspot" sites for sex work nationally, and matched sites into strata in which the prevalence of sex work from sites with PSEs was applied to those without. Directly and indirectly estimated PSEs for all hotspot sites were summed to provide a national-level PSE, incorporating an adjustment accounting for sex work outside hotspots.

Results: Median site PSEs ranged from 12,863 in Harare to 247 in a rural growth-point. Multiplier methods produced the highest PSEs. We identified 55 hotspots estimated to include 95% of all FSW. FSW nationally were estimated to number 40,491, 1.23% of women aged 15-49 years, (plausibility bounds 28,177-58,797, 0.86-1.79%, those under 18 considered sexually exploited minors).

Conclusion: There are large numbers of FSW estimated in Zimbabwe. Uncertainty in population size estimation should be reflected in policy-making.

PubMed Disclaimer

Conflict of interest statement

The authors have no conflicts of interest to disclose.

Figures

FIGURE 1.
FIGURE 1.
Log population size estimates and 95% confidence intervals for each of the 20 sites by method.
FIGURE 2.
FIGURE 2.
Distribution of the estimated (directly estimated and extrapolated) size of the female sex worker population at 55 hotspot sites.
See this image and copyright information in PMC

References

    1. Baral S, Beyrer C, Muessig K, et al. Burden of HIV among female sex workers in low-income and middle-income countries: a systematic review and meta-analysis. Lancet Infect Dis. 2012;12:538–549. - PubMed
    1. Pruss-Ustun A, Wolf J, Driscoll T, et al. HIV due to female sex work: regional and global estimates. PLoS One. 2013;8:e63476. - PMC - PubMed
    1. Prudden HJ, Watts CH, Vickerman P, et al. Can the UNAIDS modes of transmission model be improved? A comparison of the original and revised model projections using data from a setting in west Africa. AIDS. 2013;27:2623–2635. - PMC - PubMed
    1. Guidelines on Estimating the Size of Populations Most at Risk to HIV. Geneva, Switzerland: World Health Organisation and UNAIDS; 2010.
    1. Wesson P, Reingold A, McFarland W. Theoretical and empirical comparisons of methods to estimate the size of hard-to-reach populations: a systematic review. AIDS Behav. 2017;21:2188–2206. - PubMed

Publication types