Estimates of the Size of Key Populations at Risk for HIV Infection: Men Who Have Sex with Men, Female Sex Workers & Injecting Drug Users in Nairobi, Kenya

Objectives

Size estimates of populations at higher risk for HIV infection are needed to help policy makers understand the scope of the epidemic and allocate appropriate resources. Population size estimates of men who have sex with men (MSM), female sex workers (FSW) and intravenous drug users (IDU) are few or non-existent in Nairobi, Kenya.

Methods

We integrated three population size estimation methods into a behavioural surveillance survey among MSM, FSW and IDU in Nairobi during 2010–2011. These methods included the multiplier method, ‘Wisdom of the Crowds’ and an approach that drew on published literature. The median of the three estimates was hypothesised to be the most plausible size estimate with the other results forming the upper and lower plausible bounds. Data were shared with community representatives and stakeholders to finalise ‘best’ point estimates and plausible bounds based on the data collected in Nairobi, a priori expectations from the global literature and stakeholder input.

Results

We estimate there are approximately 11 042 MSM with a plausible range of 10 000–22 222, 29 494 FSW with a plausible range of 10 000–54 467 FSW and approximately 6107 IDU and plausibly 5031–10 937 IDU living in Nairobi.

Conclusions

We employed multiple methods and used a wide range of data sources to estimate the size of three hidden populations in Nairobi, Kenya. These estimates may be useful to advocate for and to plan, implement and evaluate HIV prevention and care programmes for MSM, FSW and IDU. Surveillance activities should consider integrating population size estimation in their protocols.

Population size estimates of MSM, FSW and IDU using literature and demographic data, Nairobi, November 2010

Population	Denominator	N (a)	Source of denominator	Estimate of prevalence in population* (b), %	Source of prevalence estimate	Estimate a* b
MSM	Men 18+	1 133 998	2009 Nairobi Census	1.2	Caceres et al (2008)	13608
FSW	Women 18+	1 053 368	2009 Nairobi Census	2.8	Vandepitte et al (2006)	29494
IDU	Adults 18+	2 187 366	2009 Nairobi Census	0.3	Aceijas et al (2006)	6562

*Of adult men for MSM, of adult women for FSW and of all adults for IDU.

FSW, female sex workers; IDU, intravenous drug users; MSM, men who have sex with men.

Below:  Population size estimates of high-risk populations, Nairobi, Kenya for 2010/11. (A) MSM population size estimates, median and plausibility bounds, Nairobi, 2010. (B) FSW population size estimates, median and plausibility bounds, Nairobi, 2010. (C) IDU population size estimates, median and plausibility bounds, Nairobi, 2011. Access the article online to view this figure in colour.

Full article at:   http://goo.gl/Vk0vt1

By:  Jerry Okal,1 Scott Geibel,1 Nicolas Muraguri,2 Helgar Musyoki,2 Waimar Tun,3 Dita Broz,4 David Kuria,5 Andrea Kim,6Tom Oluoch,6 and H Fisher Raymond7

¹Population Council, Nairobi, Kenya

²National AIDS and STD Control Programme, Nairobi, Kenya

³Population Council, Washington, DC, USA

⁴Division of Global HIV/AIDS, Centers for Disease Control and Prevention, Atlanta, Georgia, USA

⁵Gay and Lesbian Coalition of Kenya, Nairobi, Kenya

⁶Division of Global HIV/AIDS, Centers for Disease Control and Prevention, Nairobi, Kenya

⁷San Francisco Department of Public Health, HIV AIDS Statistics and Epidemiology, San Francisco, California, USA

Correspondence to: H Fisher Raymond, San Francisco Department of Public Health, HIV AIDS Statistics and Epidemiology, San Francisco, CA 94102, USA;

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