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Washing Penis Soon After Sex Increases Risk of HIV Among Uncircumcised Men, Study Says

August 21, 2007

Washing the penis minutes after sex might increase the risk of HIV infection among uncircumcised men, according to a study funded by NIH's National Institute of Allergy and Infectious Diseases and presented on July 25 at the 4th IAS Conference on HIV Pathogenesis, Treatment and Prevention in Sydney, Australia, the New York Times reports. According to the Times, the washing analysis was the secondary part of a study undertaken to determine the effectiveness of male circumcision as an HIV prevention method.

For the study, Fredrick Makumbi of the Makerere University Institute of Public Health and colleagues examined 2,552 uncircumcised, HIV-negative men ages 15 to 29 in the Rakai district of Uganda. Eighty-three percent of the participants said they washed their penises with all sex partners, the Times reports. The researchers asked the men when and how they washed their penises -- including if they washed with or without cloths -- after sex at the beginning of the study and at six, 12 and 24 months after the study began. According to Ronald Gray, a study co-author and professor of population and family planning at Johns Hopkins Bloomberg School of Public Health, the researchers did not ask details about how the washing was conducted or if soap was used because of an oversight. Some soaps used in Africa are more irritating than soaps used in other places, according to the Times.

The researchers found that men who washed within three minutes after sex had a 2.3% risk of HIV infection, compared with a 0.4% risk among men who delayed washing for 10 minutes or more. Makumbi and other AIDS experts said they do not know why washing might increase vulnerability to HIV, but they offered some explanations. One is that delaying washing and prolonging exposure to vaginal secretions might reduce viral infectivity. Another explanation is that the acidity of vaginal secretions might impair the ability of HIV to survive on the penis, the Times reports. In addition, the use of water, which has a neutral pH, might prolong viral survival and possible infectivity, according to the Times. HIV likely needs to be in a fluid to cross the mucosa and infect cells, Gray said, adding that if HIV-infected fluid dries, its infectivity could decrease. Adding water, therefore, could resuspend HIV and increase its infectivity, the Times reports.

One message from the study is that "there ought to be a little time left for postcoital cuddling before you go and wash," Gray said, adding, "Don't just finish and jump out of bed." Merle Sande -- an infectious disease expert at the University of Washington-Seattle and president of the Academic Alliance Foundation, a group that trains health workers to treat HIV/AIDS and other infectious diseases in Uganda -- said the study's findings are counterintuitive and "show why you have to do the studies, because until you do them, you just don't know." He added, "There is still so much we don't understand about the complex factors that influence HIV transmission in the genital tract, but this important study will help" (Altman, New York Times, 8/21). served as the official webcaster of the IAS conference. Individuals can find more information about conference webcasts online.

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