Human retroviruses: a decade of discovery and link with human disease

Article Abstract:

Living cells, including bacteria and viruses, contain DNA (deoxyribonucleic acid, the genetic material). The DNA is used to make RNA (ribonucleic acid), and the RNA is used to make proteins that are necessary for the cell or microorganism to survive. Retroviruses are different. They have a special enzyme (reverse transcriptase) that allows them to use RNA to make DNA. These viruses can cause disease and cancer in humans. They can be passed from person to person by sexual contact, intravenous drug use, and blood transfusions. The first human retroviruses were identified in the late 1970s. The human T cell leukemia virus (HTLV) and the human immunodeficiency virus (HIV) were the first to be identified. There are two different types of each of these viruses: HTLV-I, HTLV-II, HIV-1, and HIV-2. The HTLV most likely originated in Africa. It causes leukemia, polymyositis (inflammation in muscles), and a neurological disease similar to multiple sclerosis that results in muscle weakness and paralysis. The HIV causes AIDS. It attacks and destroys the immune system (the body's natural defense system for fighting infection). It does this by infecting and destroying cells called T lymphocytes (also called CD4+ cells). There are two different types of tumors associated with the HIV: B cell lymphoma and Kaposi's sarcoma (a type of tumor found in the skin and lymph nodes). The exact cause of Kaposi's sarcoma has not been identified, but it occurs in homosexuals who are infected with HIV. (Consumer Summary produced by Reliance Medical Information, Inc.)

Physiological aspects, Retroviruses, HTLV infections

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Is the incubation period of AIDS lengthening?

Article Abstract:

It has been suggested that the length of time from infection with the human immunodeficiency virus (HIV) to development of AIDS is increasing; this could be due to treatments with drugs, behavioral changes that reduce the rates of reinfection, or other reasons. Results from a study of 1,637 homosexual men from Los Angeles were analyzed and showed that the incubation time (the time from HIV infection to the onset of AIDS) is getting longer, but this trend was not statistically significant. Based on these data, the overall proportion of individuals who developed AIDS within six years after infection was 27 percent. However, if July 1987 is used as the time that the length of the incubation period started to change, the proportion of individuals infected in the first half of 1979 who developed AIDS in six years was 28 percent and the proportion for the first half of 1983 was 25 percent. Possible reasons for a lengthening of the incubation period include: that treatments are delaying the onset of AIDS; that changes in behavior of high-risk groups is lowering the risk of reinfection with HIV and the acquisition of other agents that may be cofactors of the disease; that people, including those infected, are taking better care of their health; and that the virus, and the resulting disease, have changed over time. (Consumer Summary produced by Reliance Medical Information, Inc.)

Development and progression, Behavior, Gay men, AIDS (Disease)

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