Female-to-female sexual transmission

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 five 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).

One of the most thoroughly investigated reports concerns a woman who had a monogamous sexual relationship lasting nearly two years with a woman who died of AIDS in 1989. Sexual activity consisted of mutual fingering, oral sex and use of a shared sex toy. In 1987 the patient developed vaginal herpes; her partner was not suffering from herpes. In April 1988 the woman developed what appears to have been a seroconversion illness. Upon the death of her partner in 1989 the woman tested HIV-positive. She had a relatively high CD4 count, suggesting that she had been infected recently. The woman denied any activity which could have put her at risk for HIV infection apart from sexual contact with her deceased partner.¹

It is sometimes argued that no large-scale epidemiological investigation of HIV prevalence amongst lesbians has taken place. However, three studies of the source of infection of all women with AIDS in the US have failed to identify any cases of woman-to-woman transmission.^{2 3 4} 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.⁵

These studies suggest that whilst lesbians may be infected with HIV through sexual intercourse with men or through shared injecting equipment, there is very little risk that they will transmit the virus to other women during sexual intercourse.

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.⁶

In January 2003 a case report of female-to-female sexual HIV transmission was reported in the journal Clinical Infectious Diseases.⁷ 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.

The case concerns a 20-year-old woman, from Philadelphia, 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.

A medical examination established that the woman was in good health with no evidence of injecting drug use, or nasal damage from cocaine snorting. The woman also had good oral health, which physicians took to mean that oral transmission could be ruled out.

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 note 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".

Risk factors which have been suggested in sex between women include:

• Oral sex.
• Sharing of sex toys.
• Fisting, particularly if blood is drawn.