Study suggests link between HIV therapy and syphilis outbreaks

Drugs used to prevent and treat HIV could be contributing to a dramatic rise in syphilis cases, according to a new study co-authored by a University of Victoria microbiologist.

Syphilis cases have risen sharply in recent years, primarily affecting men who have sex with men. This increase has been attributed to more-risky sexual behaviour, but the increase of syphilis is outpacing that of other sexually transmitted diseases.

The study team, which includes UVic microbiologist Caroline Cameron, theorizes that this increase might be partly connected to drugs used for treatment and prevention of HIV infection.

The study, published on Jan. 16 in BMJ Sexually Transmitted Infections, suggests that antiretroviral therapy (HAART) medications for treating HIV may affect the body’s immune response to certain diseases, including syphilis.

“What we’re hypothesizing is that there is an additional reason, besides behaviour, for why we’re seeing this increase in syphilis cases,” says Cameron, who is one of a handful of researchers in the world who studies the syphilis bacterium and how it spreads.

“HAART has been transformational in the battle against HIV,” she says. “If further study confirms our hypothesis, we’ll have yet another reason to intensify the fight against syphilis.”