Since reports of the human immunodeficiency virus (HIV) virus began to emerge in the United States in the 1980s, the HIV epidemic has frequently been linked to gay, bisexual, and other men who have sex with men (MSM) by epidemiologists and medical professionals.en who have sex with men (abbreviated as MSM, also known as males who have sex with males) are male persons who engage in sexual activity with members of the same sex, regardless of how they personally identify themselves.