A 46-year-old woman in Texas likely acquired HIV after having a sexual relationship with her female partner in what officials say is a very rare case of female-to-female transmission of the HIV.

The two women had been in a monogamous sexual relationship for six months; one of them had been infected with HIV and had not taken her medication in two years, according to a new case report by the Centers for Disease Control and Prevention, Fox News reported.

The second woman did not have other risk factors for HIV: she had not had heterosexual sex in 10 years, and she did not use injection drugs.

HIV can be present in vaginal fluid and menstrual blood, which makes the transmission of the virus between two women theoretically possible, the researchers said.

The report has been published in CDC's Morbidity and Mortality Weekly Report.