When considering the issue of female-to-female sexual transmission it is important to draw a distinction between the risk of transmission by this route and diagnoses of HIV infection in women who identify as lesbian. There have been only six reported cases of woman-to-woman sexual transmission, and these reports need to be viewed with the same caution as any other case reports of transmission through oral sex (cunnilingus).
In the early years of the epidemic, investigations of the source of infection in US women failed to identify any cases of female-to-female transmission. For example, a 1992 follow-up of all 144 women identified as HIV-positive through the blood donation services in the US interviewed 106 women, and identified only three who had had sex with women. All of these women had other risk factors: either injecting drug use or vaginal intercourse with men (Chu).
An Italian study of 18 HIV-discordant lesbian couples who had been monogamous partners for at least three months prior to recruitment and who were followed for six months found no seroconversions occurred during this period. Three-quarters of the couples reported sharing sex toys and virtually all couples reported oral sex (Raiteri).
Human immunodeficiency virus, the virus which causes AIDS. There are two variants: HIV-1, and HIV-2. HIV-1 is by far the most common worldwide. See ‘subtype’ for more information.
Abbreviation of a Latin term meaning every night.
See absolute risk: The chance that a person will experience a specific event during a period of time. It is always between 0 and 1 (when expressed as a probability), or between 0 and 100 (when expressed as a percentage).
A level of viral load that is too low to be picked up by the particular viral load test being used or below an agreed threshold (such as 50 copies/ml or 200 copies/ml). An undetectable viral load is the first goal of antiretroviral therapy.
Measurement of the amount of virus in a blood sample, reported as number of HIV RNA copies per milliliter of blood plasma. Viral load is an important indicator of HIV progression and of how well treatment is working.
In 2003 a case report of female-to-female sexual HIV transmission was published. Doctors suggest the woman may have been infected through sharing sex toys after drug-resistance tests found striking similarities between the genotypes of the woman and her female HIV-positive partner (Kwakwa).
The case concerns a 20-year-old woman who presented with HIV infection having had a negative HIV test result six months earlier. The woman had been in a monogamous lesbian relationship for the past two years, and denied having had any other sexual partners, male or female. She had never injected drugs or received blood products, and had no tattoos or body piercings. The couple’s sexual practices included the sharing of sex toys, and oral sex. These activities did not occur during menstruation, but sex toys had occasionally been used vigorously enough to draw blood.
Her bisexual partner was known to be HIV positive, and is believed to be the source of infection because of similarities observed when the two women underwent genotypic drug-resistance tests. The 20-year-old woman was infected with multidrug-resistant HIV.
The investigators noted that this is the "first reported case of female-to-female sexual transmission of HIV supported by identification of similar HIV genotypes in the source patient and the recipient".
In 2014, a further case report was published, on this occasion supported by phylogenetic analysis, which showed that the genetic sequences of the viruses infecting the two women were highly related (Chan).
The report concerns a 46-year-old woman who appears to have acquired HIV during a six-month monogamous HIV serodiscordant sexual relationship with a 43-year-old woman. She had had a negative antibody test a few weeks before seroconversion illness and diagnosis.
Her female partner had been previously diagnosed with HIV but had dropped out of medical care and was not receiving antiretroviral therapy. The newly diagnosed woman had no other recent risk factors for HIV, such as heterosexual intercourse, injecting drug use, or more unusual modes of HIV transmission such as tattooing, acupuncture, transfusion or transplant.
The couple reported routinely having unprotected oral and vaginal contact and using insertive sex toys that were shared between them. They described their sexual contact as at times rough to the point of inducing bleeding and contact with menstrual blood.
The last two case reports both involved sharing of sex toys and exposure to blood during sex.
Chu SY et al. Update: epidemiology of reported cases of AIDS in women who report sex only with other women, United States 1980–1991. AIDS 6: 516–519, 1992.
Raiteri R et al. No HIV–1 transmission through lesbian sex. Lancet 344: 270, 1994.
Kwakwa HA et al. Female-to-female transmission of human immunodeficiency virus. Clinical Infectious Diseases 36:E40-41, 2003. You can read more about this study in our news report.
Chan SK et al. Likely female-to-female sexual transmission of HIV – Texas 2012. MMWR Weekly Report, 63(10): 209-12, 2014. You can read more about this study in our news report.
