Friday, July 20, 2007

To Cut or Not to Cut

A Modeling Approach for Assessing the Role of
Male Circumcision in HIV Control.

Podder CN, Sharomi O, Gumel AB, Moses S.
Department of Mathematics, University of Manitoba, Winnipeg, MB, R3T
2N2, Canada

Bull Math Biol. 2007 Jun 8

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.