People with multiple sex partners are more at risk than monogamous couples, particularly if a condom is not used (even once with one of the partners). The more sex partners a person has had unprotected sex with, the higher the likelihood that that person has been exposed to HIV and other STDs (sexually transmitted diseases).

At particular risk among people with multiple sex partners are sex workers. Sex workers are at an especially high HIV risk because their lifestyles often include high rates of partner change, low prevalence of condom use, and high levels of sexually transmitted infections (STIs). These three factors lead to an extremely efficient spread of HIV infection, which progresses through broad sexual networks at very rapid rates, reaching multiple clients, spouses and associated sexual partners, children, and other sex workers.

It is very difficult to provide sex worker communities with information about HIV/AIDS and access to HIV/AIDS services because these communities exist in so many different forms and levels of visibility, depending on the police, religious institutions, local and national laws, public health resources, and local or national attitudes to sex work. In many communities, sex workers are marginalized, stigmatized, and made to live as criminals, occupying an unclear and often “invisible” social and legal status. As a result, sex workers are also particularly vulnerable to violence and sexual exploitation.

Because of the double stigma placed on their occupation and on HIV/AIDS as a disease, sex workers are often the most reluctant demographic in seeking out information and/or services for prevention or care of HIV/AIDS. The structure of the sex worker industry also contributes to the high HIV risk factor, since competition is rampant in the industry and working conditions are often exploitative and isolating, which leaves the individual sex worker with very limited control over his/her own life and reproductive choices.