Male circumcision could significantly reduce the burden of HIV in Africa, a study suggests.
Circumcision had been practised for many centuries
It concluded that the operation could avert about six million HIV infections and three million deaths in sub-Saharan Africa over the next 20 years.
The findings build on research, published in 2005, that suggested circumcision reduced HIV infection risk in heterosexual men by about 60%.
The research is published in the journal PLoS Medicine.
An international team of researchers used data on HIV infection rates and the prevalence of male circumcision across Africa to predict the potential impact.
Using mathematical modelling, they looked at what would happen if, over the next 10 years, all men in sub-Saharan Africa were circumcised.
They calculated that within a decade some two million new HIV infections and 300,000 deaths could be prevented. And in the ten years after that, a further 3.7 million infections and 2.7 million deaths could be avoided - with one in four of the deaths prevented being in South Africa.
The greatest reduction in infection would be for men, but this would have a knock-on effect for women.
Catherine Hankins, chief scientific adviser to the United Nations Programme on HIV/Aids (UNAIDS) and a co-author on the study, said: "The big message from the paper is that there is a tremendous potential for male circumcision to have an effect on the HIV epidemic, particularly in sub-Saharan Africa.
She said the team would now like more data from new trials that are being undertaken, especially on male-to-female transmission, to further refine the model and to help inform decisions about whether and how to promote male circumcision for HIV prevention.
"Safety, acceptability and cost of male circumcision will also be important beyond just modelling this impact, because if you do not get increased uptake you will not see any of these effects."
Currently, she said, circumcision in sub-Saharan Africa varied greatly per country: "In west and central Africa have high circumcision rates and lower HIV rates. Southern and eastern Africa have lower circumcision rates and higher HIV rates."
Deborah Jack, chief executive of the National AIDS Trust, said: "These findings are encouraging and it is clear the promotion of voluntary circumcision can play an important role in reducing the risk of HIV transmission, as part of a comprehensive prevention programme.
"However, people who are circumcised can still be infected with HIV and any awareness campaign would have to be extremely careful not to suggest that it protects against HIV or is an alternative to using condoms."