female-to-female sexual transmission of HIV

MMWR came out today with very likely case of female-to-female transmission of HIV, although it is apparently a quite rare form of transmission (see http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6310a1.htm?s_cid=mm6310a1_e ). basically, one of the women had known HIV and stopped taking antiretrovirals in 2010.  there was a 6-month monogamous relationship between this woman and an HIV-negative one. the woman who acquired the infection had no injection drug use, tattoos, acupuncture, and had 3 female sexual partners in prior 5 years. for $$, she sold her plasma and had tested HIV neg after donating in March 2012. 10 days later had sx of acute HIV, went to the ER and had neg HIV antibody screen (EIA) -- no viral load done. 18 days later, she went to sell plasma again but was positive by EIA for HIV ab and western blot. to confirm the likelihood of female-to-female transmission, genetic analysis was done on both viruses, the virus transmitted was virtually identical (>98% of HIV sequence in 3 genes) to the HIV virus of the positive woman. the couple had unprotected oral and vaginal contact and used insertive sex toys shared between them but not with other people. also sex occasionally leading to some bleeding as well as during menses.

so, this is a pretty definite case. prior cases (though few and anecdotal) have been hard to document that there were not other risk factors involved.  in study of 960,000 female blood donors, 144 women tested positive, 106 interviewed and 102 were heterosexual, 3 bisexual, and 1 with hx of IDU. so, pretty rare transmission between women. but bottom-line is: it can happen and women who have sex with women should be aware of the possibility and consider barrier protection (esp if couple is discordant for HIV).