Men who have not been circumcised (search) may be more than twice as likely to become infected with HIV (search) after sex with an infected female partner, according to a new study.

Researchers say it’s the first study to compare the risk of HIV infection per heterosexual sex act among a group of men with multiple sexual partners.

They say the results may help explain the rapid spread of HIV in areas of the world where circumcision is not common and multiple sexual partners are, such as Africa.

Male Circumcision May Lower HIV Infection Risk

For the study, which appears in the Feb. 15 issue of The Journal of Infectious Diseases, researchers collected information on sexual behavior from 745 Kenyan truck drivers.

The men were tested for HIV infection and evaluated for circumcision status at the start of the study and followed from 1993 to 1997.

During the course of the study, the truck drivers provided information concerning the number of sexual encounters with wives, casual partners, and prostitutes and were screened for HIV and other sexually transmitted diseases.

At the end of the study, researchers calculated the probability of HIV infection per sex act using published data on the rates of HIV infection among the three types of sexual partners.

The results showed that the probability of the men in the study becoming infected with HIV after a single act of sexual intercourse was about one in 160. But uncircumcised men had more than twice the rate of HIV infection per sex act compared with circumcised men, one in 80 vs. one in 200.

Researchers say the rate of HIV infection from women to men in this study was much higher than in previous studies of couples in which the woman was infected and the man was not.

They say the higher HIV infection rates among men with multiple simultaneous sexual partners may help explain the rapid spread of HIV in Africa, where multiple sexual partners are common and male circumcision is rare.

By Jennifer Warner, reviewed by Brunilda Nazario, MD

SOURCES: Baeten, J. The Journal of Infectious Diseases, Feb. 15, 2005; vol 191: pp 546-553. News release, Infectious Diseases Society of America.