Circumcised men may be much less likely to contract HIV, the virus that causes AIDS, through sex with infected women, a new study says.

Speaking yesterday at an International AIDS Society conference in Rio de Janeiro, Brazil, French AIDS researcher Bertran Auvert presented the study's findings, which are based on 3,273 South African men.

The results show that circumcised men in the study were 63 percent less likely than uncircumcised men to be infected through sex with HIV-positive women. That's a far better level of protection than the 30 percent reduction risk set as a target for an AIDS vaccine.

Auvert urged the promotion of circumcision as a public health initiative in Africa. "The first thing to do is to offer safe male circumcision to those who want to be circumcised. We must adapt the health system so that it can afford male circumcision," said Auvert, who works for the National Institute of Health and Medical Research in Saint-Maurice, France.

Robert Bailey, an epidemiology professor at the University of Illinois at Chicago, hailed the study as a wakeup call.

"If the international public health community was not alert before, this will surely wake them up to a possible intervention that could be more effective than any vaccine that might be developed over the next ten years," he said.

Bailey is leading a similar study, funded by the U.S. National Institutes of Health, in Kenya.

Best Evidence Yet

The idea that male circumcision provides significant protection against HIV infection is not new.

Several dozen previous studies in Africa have shown that circumcised men are two to nine times less likely to become infected by women with the virus than uncircumcised men are. But with its sample group of 3,000 men, Auvert's study is by far the most extensive to date.

"Male circumcision must be recognized as an important means to fight the spread of HIV infection and the international community must mobilize to promote it," Auvert wrote in the abstract of his presentation in Rio de Janeiro.

Health officials have hesitated to integrate circumcision with other HIV-prevention strategies, because the practice has strong cultural and religious implications. The procedure also carries the risk of complications if performed incorrectly or in unsanitary conditions.

Male circumcision, the surgical removal of the foreskin of the penis, is common in the United States. It is not, however, practiced regularly in many other regions of the world, including Asia and parts of Europe.

In Africa about 70 percent of men are circumcised, mostly according to ethnic affiliation. The practice is performed at birth or during rite-of-passage ceremonies in early puberty.

Africa has the highest HIV/AIDS infection rates in the world, with more than 25 million people infected.

French and South African researchers began the newly released study in August 2002. Their subjects were HIV-negative men ages 18 to 24 in the South African township of Orange Farm, south of Johannesburg.

Half of the men in the study were randomly assigned to be circumcised, while the other half remained uncircumcised. The researchers found that, for every ten uncircumcised men in the study who contracted HIV, only about three uncircumcised men did so.

"This is very dramatic," Bailey said—so dramatic that the study was stopped in February, nine months before completion. The researchers had decided it would be unethical to proceed without offering the uncircumcised control group the chance to undergo the procedure.

Why Circumcision May Work

Medical anthropologists noticed as early as 1989 that the highest HIV infection rates in Africa were occurring in regions where the predominant cultures did not practice male circumcision. Since then some 35 studies have suggested a relationship between male circumcision and lower HIV infection rates.

Adult HIV infection rates are above 30 percent in Zimbabwe, Botswana, and eastern South Africa—areas where male circumcision is not generally practiced. Meanwhile, infection rates are below 5 percent in most of West Africa, where male circumcision is commonplace.

The reason for the increased risk of infection, experts say, is because the foreskin of the penis is susceptible to scratches and tears during intercourse. In addition, the foreskin contains a high density of Langerhans cells, which are especially vulnerable to HIV.

Circumcision may also prevent other sexually transmitted diseases, including syphilis and herpes, which are known to increase the likelihood of HIV infection.

There were almost five million new HIV infections worldwide last year. Other than abstinence and safer sex, almost nothing has been proved to reduce the sexual spread of HIV. A vaccine may be 20 years away, according to some estimates.

Cultural Practice

Male circumcision could be a powerful way to reduce the spread of the disease, many experts say. However, getting people to change their cultural and religious practices is notoriously difficult.

"About two-thirds of the world's men are not circumcised," said Bailey, the Illinois epidemiologist. "Many of these are understandably reticent to consider a procedure that they have not experienced themselves and which they may view as risky and painful."

But studies have shown that most men and women in traditionally non-circumcising regions of Africa prefer males to be circumcised if the procedure is done safely and affordably.

In a survey of 216 adults in Kenya, Bailey found that 60 percent of men would prefer to be circumcised and that 62 percent of women would prefer circumcised partners, but only about 10 percent of men actually have the procedure done.

However, the benefits of male circumcision must be weighed against the potential harm, Bailey says. When done properly, circumcision is a simple outpatient procedure. But in unsafe conditions, complications can arise.

"There are many horror stories of young boys and men suffering profuse bleeding, advanced infections, and even mutilation and death," Bailey said. "Most of these incidents have been associated with circumcisions done by untrained practitioners, especially traditional circumcisers in East and southern Africa."

Health experts also worry that many men might think circumcision will completely protect them from AIDS, causing them to take increased risks in their sex lives.

Still, Bailey says, AIDS experts in Africa are much more open to promoting male circumcision than they were five to six years ago.

"Given all these benefits which have become more widely known in recent years, it is not so surprising that the scientific and public health communities are paying more attention to this potentially effective prevention tool," Bailey said.

Despite the encouraging new statistics, Auvert, the study leader, warns that his report is far from the final word. "It's too early to say male circumcision should be integrated in a plan to fight the spread of HIV, because the study has only been done in one place."

Soon enough, though, results of similar studies should be arriving from other African countries and may cement Auvert's South African findings.

For Maria Wawer, a professor of clinical public health at Baltimore, Maryland's Johns Hopkins University, Auvert's study is only the beginning. Addressing the possibility of similar results from studies in Kenya and Uganda, she said, "This would be wonderful, since, if the two ongoing studies replicate the South African finding, it will provide evidence that circumcision is highly effective in diverse settings."