People who use the Internet to find real-life sex partners are more likely to have had sexually transmitted diseases or engaged in risky intimate behavior, a government-led study found.

Another study, based on San Francisco's handling of syphilis cases linked to an Internet chat room, suggests the Internet can help public health officials curb disease outbreaks. Both studies appear in Wednesday's Journal of the American Medical Association. In the first study, led by Centers of Disease Control researcher Mary McFarlane, investigators looked at the habits of 856 clients at a Denver HIV testing and counseling center. Nearly 16 percent — 135 subjects — reported seeking sex partners online. Nearly a third of those online seekers said they had contracted sexually transmitted diseases and had been exposed to HIV-positive sex partners. In comparison, 20 percent of those who tried to find partners in more conventional ways said they'd had venereal diseases and just 14 percent said they'd had HIV-positive partners. A JAMA editorial said the findings weren't surprising, since the anonymity of sex facilitated by the Internet would be expected to appeal to "sexual adventurers" willing to take risks. The San Francisco health officials determined last year that two men may have contracted syphilis from partners they met online. Because the patients said they knew only their partners' chat room aliases, officials couldn't use conventional methods of tracking them down or alerting others about the danger. With help from the service provider that hosted the chat room, officials posted alerts there encouraging men who may have met sexual partners online to seek medical evaluation. That helped them find five additional men with syphilis linked to the chat room, said the authors, led by Dr. Jeffrey Klausner of the city's public health department.