Epidemiology and clinical picture of human immunodeficiency virus type 1 infection and the acquired immune deficiency syndrome.

Human Immunodeficiency Virus Type 1 (HIV-1) infection which causes the terminal Acquired Immune Deficiency Syndrome (AIDS) is one of the major new pandemics of this millenium. This infection is believed to be a zoonosis which achieved sustained transmission among humans because of recent increases in sexual promiscuity and needle-sharing drug use. Although the HIV-1 epidemic is of relatively recent onset, its modes of transmission have been clearly defined: sexual relations, blood injection, and childbirth. Other possible transmission methods such as non-sexual social interaction and insects have been explicitly excluded. Susceptibility is increased by genital ulcers and lack of male circumcision but probably not by genetic factors or female circumcision. Transmissibility is also increased by genital ulcers and, more importantly, by the stage of disease. Progression by stages to fatal diseases will probably occur in most, if not all, infected individuals, usually within a decade. While HIV-1 has a direct effect on the intestinal track and the central nervous system, its primary effect is suppression of the immune system resulting in overwhelming secondary infections and, less clearly, cancers. Human Immunodeficiency Virus Type 1 infection is incurable and is likely to remain so for the foreseeable future. Although life-prolonging treatments have been developed, a vaccine will likely not be available in the foreseeable future. Like most previous new epidemic diseases, HIV-1 infection is being and will continue to be modified by changing human behavior patterns.