CDC Reports Probable Case of HIV Transmission Linked to Lesbian Sex

A woman in Texas who reported no other risk factors appears to have contracted HIV through sex with a female partner who was not on antiretroviral therapy, according to a report in the March 14, 2014, edition of the CDC's Morbidity and Mortality Weekly Report.

Epidemiological evidence suggests that HIV transmission via sex between women is very uncommon. While there have been anecdotal reports of woman-to-woman sexual transmission, in almost all cases other risk factors are known or cannot be ruled out. Almost all lesbian and bisexual women with HIV have other risk factors such as sex with men or injection drug use. But woman-to-woman sexual transmission is potentially possible through exposure to HIV in cervical-vaginal fluid or blood from menstruation or rough or traumatic sex.

As described in the MMWR report, in August 2012 the Houston Department of Health contacted the U.S. Centers for Disease Control and Prevention (CDC) about a rare case of HIV transmission via sexual contact between 2 women.

The newly infected woman, age 46, was regularly tested for HIV when she sold blood plasma, and had tested negative by enzyme immunoassay (EIA) antibody screening in March 2012. She went to the emergency room in April with upper respiratory and flu-like symptoms -- where she again tested HIV negative -- and was treated with antibiotics. But 18 days later, she tested positive for HIV antibodies at the plasma facility, which was confirmed by repeated EIA and Western blot tests.

The case was investigated and laboratory testing confirmed that the newly diagnosed woman had the same virus strain as her female partner (>98% genetically identical). The partner had been diagnosed with HIV in 2008, but had stopped taking antiretroviral therapy 2 years later.

The newly positive woman reported that she had been in a monogamous relationship with her partner for 6 months. She said she had not had heterosexual intercourse during the previous 10 years and had no history of injection drug use, blood transfusions, or receiving tattoos or acupuncture. The couple reported that they routinely engaged in oral and vaginal sex and shared sex toys without using barriers such as dental dams or gloves. They said they had sex during menstruation and their sexual contact was sometimes rough enough to cause bleeding

The report authors reviewed previous cases of suspected woman-to-woman sexual transmission. Large surveys of women with HIV have found none who reported sex with women as their sole possible risk factor. "Past confirmation of HIV transmission during female-to-female sexual contact has been difficult because other risk factors almost always are present or cannot be ruled out," they wrote. "In this case, other risk factors for HIV transmission were not reported by the newly infected woman, and the viruses infecting the two women were virtually identical."

"Although rare, HIV transmission between [women who have sex with woman] can occur," the authors concluded.

The self-reported nature of the newly infected woman's risk factors is a limitation of this report. While the genetic similarity of their virus rules out some competing risks -- such as sex with men outside the relationship or exposure via tattooing or medical procedures -- it remains possible that the women could have shared needles or other injection drug equipment, and they may have failed to report such stigmatized and criminalized behavior.

"All persons at risk for HIV, including all discordant couples, should receive information regarding the prevention of HIV and sexually transmitted infections to prevent the HIV negative partner from acquiring the infection," the authors wrote. "Furthermore, all persons identified as infected with HIV should be linked to and retained in medical care. Control of HIV infection with suppression of viral load can result in better health outcomes and a reduced chance of transmitting HIV to partners."

The report notes that the women had not received any prevention counseling prior to the probable transmission, and the authors emphasized that all mixed-status couples should receive counseling regarding safer sex practices.

Barriers such as dental dams for oral sex and gloves for manual contact or fisting have been recommended as safer-sex approaches for women who have sex with women, especially in the early years of the epidemic. But given the rarity of woman-to-woman transmission, the need for barrier protection -- not to mention or other methods such as PrEP or PEP (pre- or post-exposure prophylaxis) -- remain questionable.

3/14/14

Reference

SK Chan, LR Thornton, KJ Chronister, et al. Likely Female-to-Female Sexual Transmission of HIV -- Texas, 2012. Morbidity and Mortality Weekly Report 63(10):209-212. March 14, 2014.