The AIDS epidemic, caused by HIV (Human Immunodeficiency Virus), found its way to the United States between the 1970s and 1980s, but was first noticed after doctors discovered clusters of Kaposi's sarcoma and pneumocystis pneumonia in homosexual men in Los Angeles, New York City, and San Francisco in 1981. Treatment of HIV/AIDS is primarily via the use of multiple antiretroviral drugs, and education programs to help people avoid infection.