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. 2009 Jan 2;23(1):125-30.
doi: 10.1097/QAD.0b013e3283177f20.

Heterogeneity in host HIV susceptibility as a potential contributor to recent HIV prevalence declines in Africa

Nico Nagelkerke  1 , Sake J de Vlas, Prabhat Jha, Ma Luo, Francis A Plummer, Rupert Kaul
Affiliations

Heterogeneity in host HIV susceptibility as a potential contributor to recent HIV prevalence declines in Africa

Nico Nagelkerke et al. AIDS. .

Abstract

Background: HIV prevalence has recently declined in several African countries, and prior to this the risk of HIV acquisition per unprotected sex contact also declined in Kenyan sex workers. We hypothesized that heterogeneity in HIV host susceptibility might underpin both of these observations.

Methods: A compartmental mathematical model was used to explore the potential impact of heterogeneity in susceptibility to HIV infection on epidemic behavior, in the absence of other causative mechanisms.

Results: Studies indicated that a substantial heterogeneity in susceptibility to HIV infection may lead to an epidemic that peaks and then declines due to a depletion of the most susceptible individuals, even without changes in sexual behavior. This effect was most notable in high-risk groups such as female sex workers and was consistent with empirical data.

Discussion: Declines in HIV prevalence may have other causes in addition to behavior change, including heterogeneity in host HIV susceptibility. There is a need to further study this heterogeneity and its correlates, particularly as it confounds the ability to attribute HIV epidemic shifts to specific interventions, including behavior change.

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Figures

Figure 1
Figure 1. Structure of the compartmental model
Boxes represent compartments defined by an individual's sex, risk behavior and HIV status. The model distinguishes low and high risk men and women defined by their involvement in trading sex for money. Individuals in each group can be either uninfected, be in early stage HIV, or late stage HIV. Transitions between low and high risk groups are permitted. The population is stratified by HIV susceptibility level. For each level of susceptibility different HIV transmission risks apply. An individual's level of susceptibility is treated as fixed.
Figure 2
Figure 2. Modeling the impact of heterogeneity in host HIV susceptibility on epidemic spread
(a) Modeled and empiric trends in the risk of HIV acquisition per 1000 acts of unprotected vaginal sex within the Pumwani female sex worker cohort, Nairobi, Kenya. The figure displays both empirically observed values (circles) and the results of the model (curve). (b) Modeled trend in adult HIV prevalence in male clients of female sex workers, and general population men and women, in the presence of heterogeneity in host HIV susceptibility (curves), as well as empiric HIV prevalence data from surveillance of antenatal women in Kenya (circles).
Figure 2
Figure 2. Modeling the impact of heterogeneity in host HIV susceptibility on epidemic spread
(a) Modeled and empiric trends in the risk of HIV acquisition per 1000 acts of unprotected vaginal sex within the Pumwani female sex worker cohort, Nairobi, Kenya. The figure displays both empirically observed values (circles) and the results of the model (curve). (b) Modeled trend in adult HIV prevalence in male clients of female sex workers, and general population men and women, in the presence of heterogeneity in host HIV susceptibility (curves), as well as empiric HIV prevalence data from surveillance of antenatal women in Kenya (circles).
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Comment in

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