Quantitative assessment of the role of male circumcision in HIV epidemiology at the population level.
ABSTRACT Three recent randomized trials have shown that male circumcision (circumcision) reduces HIV incidence in heterosexual men by about 60%. Mathematical models are needed to assess the historical role of circumcision in the observed disparate levels of prevalence in sub-Saharan Africa and to translate these findings into estimates of the population-level impact of circumcision on HIV prevalence.
A deterministic compartmental model of HIV dynamics with circumcision was parameterized by empirical data from the Rakai, Masaka, and Four-City studies. Circumcision was found to account for about two-thirds of the differential HIV prevalence between West Africa and East and Southern Africa. We found that in Kisumu, Kenya, and in Rakai, Uganda, universal circumcision implemented in 2008 would reduce HIV prevalence by 19% and 14%, respectively, by 2020. In Kisumu, a setting with high HIV prevalence, about 6 circumcisions would be needed for each infection averted while in Rakai, 11 circumcisions would be needed. Females will also benefit from circumcision with a substantial reduction in prevalence of about 8% in Kisumu and 4% in Rakai within a few years of universal circumcision. The beneficial impact of circumcision for both males and females will not be undermined by risk behavior compensation unless the increase in risk behavior is in excess of 30%. The effectiveness of circumcision as an intervention is maximized by universal circumcision within 2-3 years.
In West Africa, circumcision may have "quarantined" the spread of HIV by limiting sustainable transmission to within high risk groups and bridge populations. Our findings indicate that circumcision is an effective intervention in both high and intermediate HIV prevalence settings. Circumcision coverage should be expanded as soon as possible to optimize the epidemiological impact.
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ABSTRACT: A recent randomized controlled trial shows a significant reduction in women-to-men transmission of HIV due to male circumcision. Such development calls for a rigorous mathematical study to ascertain the full impact of male circumcision in reducing HIV burden, especially in resource-poor nations where access to anti-retroviral drugs is limited. First of all, this paper presents a compartmental model for the transmission dynamics of HIV in a community where male circumcision is practiced. In addition to having a disease-free equilibrium, which is locally-asymptotically stable whenever a certain epidemiological threshold is less than unity, the model exhibits the phenomenon of backward bifurcation, where the disease-free equilibrium coexists with a stable endemic equilibrium when the threshold is less than unity. The implication of this result is that HIV may persist in the population even when the reproduction threshold is less than unity. Using partial data from South Africa, the study shows that male circumcision at 60% efficacy level can prevent up to 220,000 cases and 8,200 deaths in the country within a year. Further, it is shown that male circumcision can significantly reduce, but not eliminate, HIV burden in a community. However, disease elimination is feasible if male circumcision is combined with other interventions such as ARVs and condom use. It is shown that the combined use of male circumcision and ARVs is more effective in reducing disease burden than the combined use of male circumcision and condoms for a moderate condom compliance rate.Bulletin of Mathematical Biology 12/2007; 69(8):2447-66. · 2.02 Impact Factor
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ABSTRACT: Male circumcision (circumcision) reduces HIV incidence in men by 50-60%. The United Nations Joint Programme on HIV/AIDS (UNAIDS) recommends the provision of safe circumcision services in countries with high HIV and low circumcision prevalence, prioritizing 12-30 years old HIV-uninfected men. We explore how the population-level impact of circumcision varies by target age group, coverage, time-to-scale-up, level of risk compensation and circumcision of HIV infected men. An individual-based model was fitted to the characteristics of a typical high-HIV-prevalence population in sub-Saharan Africa and three scenarios of individual-level impact corresponding to the central and the 95% confidence level estimates from the Kenyan circumcision trial. The simulated intervention increased the prevalence of circumcision from 25 to 75% over 5 years in targeted age groups. The impact and cost-effectiveness of the intervention were calculated over 2-50 years. Future costs and effects were discounted and compared with the present value of lifetime HIV treatment costs (US$ 4043). Initially, targeting men older than the United Nations Joint Programme on HIV/AIDS recommended age group may be the most cost-effective strategy, but targeting any adult age group will be cost-saving. Substantial risk compensation could negate impact, particularly if already circumcised men compensate. If circumcision prevalence in HIV uninfected men increases less because HIV-infected men are also circumcised, this will reduce impact in men but would have little effect on population-level impact in women. Circumcision is a cost-saving intervention in a wide range of scenarios of HIV and initial circumcision prevalence but the United Nations Joint Programme on HIV/AIDS/WHO recommended target age group should be widened to include older HIV-uninfected men and counselling should be targeted at both newly and already circumcised men to minimize risk compensation. To maximize infections-averted, circumcision must be scaled up rapidly while maintaining quality.AIDS (London, England) 10/2008; 22(14):1841-50. · 4.91 Impact Factor
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ABSTRACT: Recent clinical trials in Africa, in combination with several observational epidemiological studies, have provided evidence that male circumcision can reduce HIV female-to-male transmission risk by 60% or more. However, the public health impact of large-scale male circumcision programs for HIV prevention is unclear. Two mathematical models were examined to explore this issue: a random mixing model and a compartmental model that distinguishes risk groups associated with sex work. In the compartmental model, two scenarios were developed, one calculating HIV transmission and prevalence in a context similar to the country of Botswana, and one similar to Nyanza Province, in western Kenya. In both models, male circumcision programs resulted in large and sustained declines in HIV prevalence over time among both men and women. Men benefited somewhat more than women, but prevalence among women was also reduced substantially. With 80% male circumcision uptake, the reductions in prevalence ranged from 45% to 67% in the two "countries", and with 50% uptake, from 25% to 41%. It would take over a decade for the intervention to reach its full effect. Large-scale uptake of male circumcision services in African countries with high HIV prevalence, and where male circumcision is not now routinely practised, could lead to substantial reductions in HIV transmission and prevalence over time among both men and women.BMC Infectious Diseases 02/2007; 7:16. · 3.03 Impact Factor