The document discusses the causes of AIDS. It states that AIDS is caused by the human immunodeficiency virus (HIV). The virus can be transmitted sexually through blood or semen, through sharing needles, from mother to child, and through transfusions of infected blood. Those at highest risk include men who have sex with men, bisexuals, drug users who share needles, and those with multiple sexual partners. However, not all those infected with HIV will develop AIDS, as other unknown factors may be required to trigger the full disease.