Huge news in the fight against the spread of AIDS: Two studies in African countries have yielded conclusive evidence that circumcision more than halves the chances that a man will acquire an HIV infection.

AIDS experts call the findings extraordinary — as important as the initial identification of the virus and the development of life-saving treatment with drug combinations.

They predict that widespread circumcision in Africa could prevent 2 million infections and 300,000 deaths over the next 10 years. Implementation of mass circumcision, however, faces ethical and religious barriers, and too few health care workers are available to perform these numbers of safe circumcisions.

The studies, published in February in The Lancet, confirmed the results of an earlier report from South Africa which showed that circumcision reduced the risk of AIDS by 60 percent. Both studies were supported by the National Institutes of Health and were stopped early because of the strong evidence that circumcision protects against HIV.

Scientists believe that circumcision is effective because it removes tissue which contains cells that are most sensitive to infection by the HIV virus.

Circumcision presumably protects men in the U.S., as well. However, it remains critical for circumcised men to continue using condoms since circumcision does not eliminate all risk. And it is not clear whether circumcision reduces the risk that an HIV-infected man will transmit the infection to his sexual partners.