healthHealth and Medicine

Penis Foreskin Bacteria May Increase Risk Of HIV


Jonathan O'Callaghan

Senior Staff Writer

Oleksii Biriukov/Shutterstock

So, um, this is a bit awkward. But guys, if you don’t want HIV, then you really, really need to wash your… you know what.

Yes, a new study led by George Washington University in the journal mBio has found that bacteria living under the foreskin can increase one's risk of HIV. Specifically, the more anaerobic bacteria there are, the more likely an uncircumcised man will be infected with the virus.


The researchers found that a 10-fold increase in some types of bacteria living under the foreskin can increase the risk of HIV infection by a huge 63 percent.

This is the first study that has shown that penile bacteria may be an unrecognized risk factor for HIV infection. The researchers also said that this risk factor could be sexually transmissible.

"This study is the first to suggest that the bacteria colonizing the penis can be an independent risk factor for HIV in men," said Cindy Liu, lead author of the paper, in a statement. "Having more oxygen-intolerant bacteria was associated with increased HIV risk."

In the two-year-long study, penile swabs were collected from uncircumcised men in Rakai, Uganda. Of these, 46 became infected with HIV, while a control group of 136 were not infected. It was found that a 10-fold increase in four anaerobic bacteria – Prevotella, Dialister, Finegoldia, and Peptoniphilus – led to a 54 to 63 percent increase in HIV risk.


One reason for the penile microbiome increasing HIV risk might be that HIV cells are lured to the penis by the production of immune factors. Having more penile anaerobes was found to produce more biochemicals called cytokines, which recruit immune cells.

"Immune cells are HIV's gateway to the human body,” said study co-author Lance Price. “Our study suggests that some bacteria are triggering biochemical alarms that draw immune cells to the penis where they are more easily infected by HIV.”

Although it’s not clear what the next step is, the researchers hope it may be possible to selectively reduce bacteria on the penis to decrease HIV risk. Quite how this would be done isn’t clear – but washing regularly probably isn’t a bad idea.


healthHealth and Medicine
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  • hiv,

  • penis,

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  • foreskin