The human immunodeficiency virus (HIV) is a delicate organism that does not long survive outside the body. Transmission of HIV implies contact between mucosae or abraded skin and infected blood or other body fluids, including semen, breast milk, vaginal secretions, saliva (a small but real risk), and urine. Transmission may occur during unprotected heterosexual or homosexual intercourse, during vaginal delivery or breast feeding, and by way of infected blood or other body fluids, semen, saliva, vaginal secretions, or in infected body tissue, e.g., organs or tissue that is transplanted from an infected to an uninfected person. Contaminated blood is an important transmission vehicle among illicit intravenous drug users. The frequently long incubation period between primary infection with HIV and the onset of clinically diagnosable AIDS means that the virus is often transmitted from an infected, but symptom free, person to others, whether by the sexual route, needle sharing by intravenous drug users, during childbirth, breast feeding, or by some other means. This accounts for much of the explosive growth of the worldwide pandemic of HIV/AIDS since the disease first emerged in 1981. There have been several tragic surges in the epidemic, caused by use of HIV-contaminated blood and blood products in the early 1980s. See http://www.unaids.org for details.
Subjects: Public Health and Epidemiology.