Four to seven percent of these people are unaware of their HIV-positive status.
And the risk is much higher in males who have sex with other males (MSM), who constituted 64% of people living with HIV in the United States in 2012. For example, the general risk of contracting HIV from casual sex is 21 times higher in the District of Columbia, which has 46.3 HIV-positive persons per 100,000 population, than in Maine, where the prevalence is 2.2 per 100,000. In general, the risk depends mainly on the prevalence of the disease in the region where the person is engaged in casual sex activity. The risk of contracting the disease through casual sex is very hard to estimate because it depends on many variables that cannot be measured accurately, such as the number of sex acts, their timing, and other co-factors. Engaging in casual sexual activity exposes a person to HIV infection because some of those who carry the virus are not aware of their HIV-positive status and some HIV-positive individuals engage in unprotected sex without admitting that they have HIV. In the United States, the number of deaths attributed to HIV in 2017 was 34 times higher than the number of deaths attributed to all other STDs combined. While other STDs, such as chlamydia and gonorrhea, are much more common, HIV is by far the deadliest.
