There's been much talk this week at the international conference on AIDS in Melbourne about 'key affected populations'. These are groups of people who face the biggest burden of HIV but have the least access to HIV prevention, testing and treatment services.
WHO has identified them as sex workers, men who have sex with men (which covers gay men and men who are having sex with other men without necessarily identifying themselves as homosexual), those who inject drugs, prisoners and transgender people.
But what about the sexual partners of these individuals?
In a presentation on HIV in Vietnam, Theodore Hammett of Abt Associates Inc., a U.S.-based group focusing on research in health and development, argued that the sexual partners of drug users have been far too neglected in the response to HIV.
In Vietnam, 257,000 people are living with the virus that causes AIDS, and the epidemic is primarily driven by drug users.
"In Vietnam, most people who inject drugs are men and most of them are sexually active and as a result their female sexual partners may be at very high risk for transmission or acquisition of HIV," Hammett said.
In fact, in a 2007 survey of 1,300 Vietnamese women living with HIV, 88 percent of them reported getting HIV from their male partner.
Between a third and a half of the women Hammett surveyed in three places - Hanoi, Ho Chi Minh City and Dien Bien Phu - had incorrect information or lacked information about their HIV-positive male partner.
He estimates that least 10,000 female sexual partners of male drug users in the Southeast Asian country are at high risk of HIV because they don't know their partners' status.
"This risk pertains not only to sexual partners of people who inject drugs but also of any other ‘key population’," Hammett said.
"By the way, sexual partners may be female or male. But especially if they are not themselves already part of a traditional 'key population' their risks may be ignored or not correctly understood," he added.