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Background Geographic location represents an ecological measure of HIV status and is a strong predictor of HIV prevalence. Given the complex nature of location effects, there is limited understanding of their impact on policies to reduce HIV prevalence. Methods Participants were 3,949 and 10,874 respondents from two consecutive Zambia Demographic and Health Surveys from 2001/7 (mean age for men and women: 30.3 and 27.7 years, HIV prevalence 14.3% in 2001/2002; 30.3 and 28.0 years, HIV prevalence of 14.7% in 2007). A Bayesian geo-additive mixed model based on Markov Chain Monte Carlo techniques was used to map the change in the spatial distribution of HIV/AIDS prevalence at the provincial level during the six-year period, accounting for important risk factors. Findings Overall HIV/AIDS prevalence changed little over the 6-year period, but the mapping of residual spatial effects at the provincial level suggested different regional patterns. A pronounced change in odds ratios in Lusaka and Copperbelt provinces in 2001/2 and in Lusaka and Central provinces in 2007 were observed following adjustment for spatial autocorrelation. Western province went from a lower prevalence area in 2001 (13.4%) to a higher prevalence area in 2007 (17.3%). Southern province went from the highest prevalence area in 2001 (17.3%) to a lower prevalence area in 2007 (15.9%). Interpretation Findings from two consecutive surveys corroborate the Zambian government’s effort to achieve MDG 6. The novel finding of increased prevalence in Western province warrants further investigation. Spatially-adjusted provincial-level HIV/AIDS prevalence maps are a useful tool for informing policies to achieve MDG 6 in Zambia.

Reaching populations at greatest risk for acquiring HIV is essential for efforts to combat the epidemic. This paper presents, the Priorities for Local AIDS Control Efforts (PLACE) method which focuses on understanding the venues where people are meeting new sexual partners and behaviors which put people at risk. A comparison of data from two PLACE studies in Zambia with a national household survey, the Zambia Sexual Behavior Survey (ZSBS) 2005, indicated that the PLACE population was at greater risk of acquiring HIV. Respondents in the two PLACE studies were significantly more likely to report 1+ new partners in the past 4 weeks, 2+ partners in the past 12 months, 1+ new partner in the past 12 months and transactional sex. Data from the PLACE method is important for targeting interventions for those most likely to acquire and transmit HIV.

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