By Deborah Netburn, Los Angeles Times

The first confirmed case of a woman contracting  HIV from another woman during sex was reported by the Centers for Disease Control and Prevention this week.

Although there have been reports of women transmitting the human immunodeficiency virus to other women through sexual activity, they have been difficult to prove. For nearly all the cases, other risk factors were present — including recent sexual contact with men, intravenous drug use, tattooing, piercing or other, potentially risky, behaviors.

This time, the case seems pretty iron-clad.

As outlined in a paper published by the CDC this week, the two women involved were in a monogamous relationship for six months. At the start of their relationship one of the women was HIV-positive, the other was not. The woman who began the relationship HIV negative said it had been 10 years since she had had sex with a man. She did not use intravenous drugs, or get tattoos or acupuncture or transfusions or transplants.

She did, however, occasionally sell her blood plasma, and had tested negative for HIV after donating plasma in March 2012.

Ten days later, she went to the emergency room with an symptoms including sore throat, fever, muscle aches, dry cough, vomiting and frequent diarrhea. She was tested for HIV then, but the results were negative. Two and a half weeks later she went to sell her plasma again. That time she tested positive.

The two women said they had unprotected sex frequently, shared sex toys, and had sex when one of them was menstruating. Their sex also occasionally caused one or the other of them to bleed.

So the CDC concluded that it is rare but possible for a woman to get HIV from a female sexual partner.

The agency recommends that all couples in which one person is HIV-negative and one person is HIV-positive should receive counseling regarding safer sex practices — even if both parties are female.

AFP Photo/Manjunath Kiran