A possible case of HIV caused by lesbian sexual contact was reported in this week's Center for Disease Control report

According to the CDC, two women in a monogamous relationship had unprotected sex, even though one of them had HIV. They used sex toys "at times rough to the point of inducing bleeding in either woman," and engaged in sexual contact while they were on their periods. Those are the most likely ways the disease was contracted. Researchers are fairly certain the woman contracted the virus from her partner because the viruses themselves are a 98 percent match ("virtually identical," says the CDC), and because the woman did not have any of the other risk factors.

Cases of female-to-female transmitted HIV are exceedingly rare, and even the few we know of can usually be attributed to other risk factors (IV drug use or heterosexual sex, for instance). Some studies have found "no evidence" of female-to-female transmission in sample populations.

Yet in 2003, another woman contracted HIV in a similar way to today's case: "probably use of sex toys, used vigorously enough to cause exchange of blood-tinged body fluids." The report encouraged women with HIV-positive female partners to be just as safe they would if their partner was an HIV-positive male.

Those recommendations where echoed in a June 2009 report from the Gay Men's Health Center, which said "lesbians, long ignored in HIV prevention and service programs, need and deserve tailored interventions and better health outcomes."

The lesson here: everyone should practice safe sex, even if you think transmission is only theoretically possible. And be a little gentler with the sex toys.