A woman in Texas is believed to have contracted HIV in a rare case of female-to-female transmission – and campaigners say it highlights the importance of continuing with HIV medication.

The 46-year-old “likely acquired” the virus during a six-month monogamous relationship with a HIV positive woman in Texas, the US Centres for Disease Control (CDC) said on Friday.

Her partner had been diagnosed previously with HIV and had stopped receiving anti-retroviral treatment in 2010.

The couple reported routinely having unprotected oral and vaginal contact and using insertive sex toys that were shared between them but not shared with any other persons.

The originally uninfected partner is said to have had a history of heterosexual relationships but none during the past 10 years.

She also had none of the other HIV exposure risks, including intravenous drug use.

Commenting on the case, Acting Chief Executive at Terrence Higgins Trust, Paul Ward, told PinkNews.co.uk: “Sex between two women carries an extremely low risk of HIV transmission. However, in any sexual pairing, the risk of transmission increases when one of the couple has HIV but is not on treatment.

“In this case, when the HIV-positive partner stopped taking anti-HIV drugs in 2010, it is likely the amount of virus in her blood increased dramatically. Modern drug treatments don’t just keep people with HIV fit and well; they can also greatly reduce the risk of infection.”