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AIDS, byname and acronym of acquired immunodeficiency syndrome, transmissible disease of the immune system caused by the human immunodeficiency virus (HIV). HIV is a lentivirus (literally meaning “slow virus”; a member of the retrovirus family) that slowly attacks and destroys the immune system, the body’s defense against infection, leaving an individual vulnerable to a variety of other infections and certain malignancies that eventually cause death. AIDS is the final stage of HIV infection, during which time fatal infections and cancers frequently arise.
The emergence of AIDS
On June 5, 1981, the U.S. Centers for Disease Control and Prevention (CDC) published a report describing a rare lung infection known as Pneumocystis carinii pneumonia in five homosexual men in Los Angeles. Expert review of the cases suggested that the disease likely was acquired through sexual contact and that it appeared to be associated with immune dysfunction caused by exposure to some factor that predisposed the affected individuals to opportunistic infection. The following month the CDC published a report describing an outbreak of cases of a rare cancer called Kaposi sarcoma in homosexual men in New York City and San Francisco. The report noted that in many instances the cancers were accompanied by opportunistic infections, such as P. carinii pneumonia. Researchers subsequently determined that the infections and cancers were manifestations of an acquired immunodeficiency syndrome.
Initially, some researchers referred to the syndrome as gay-related immune deficiency (GRID), since it appeared to be limited to homosexuals. In the media the disease commonly was referred to as the “gay plague.” But the disease had also been detected in intravenous drug users, who became infected mainly by sharing contaminated hypodermic needles. It also had been observed in women with male sexual partners. As a result, the term acquired immunodeficiency syndrome, or AIDS, was introduced to describe the disease; the CDC published its first report using the term in 1982.
By 1984 researchers working in Africa had provided clear evidence for heterosexual transmission of the causative agent, HIV. The virus had been isolated the year before by a team of French researchers led by virologist Luc Montagnier. Montagnier and his colleagues identified the virus as a new type of human retrovirus, and they suspected that it was the cause of AIDS. But more-detailed characterization was needed to confirm the connection, so Montagnier sent samples to American virologist Robert C. Gallo, who had contributed to the discovery of the first known human retrovirus (human T-lymphotropic virus) several years earlier. Gallo helped establish that HIV caused AIDS, and he contributed to the subsequent development of a blood test for its detection. Montagnier initially called the new infectious agent lymphadenopathy-associated virus (LAV), but in 1986 the International Committee on Taxonomy of Viruses renamed it HIV. Montagnier and French virologist Françoise Barré-Sinoussi were awarded the 2008 Nobel Prize for Physiology or Medicine for their discovery of HIV; despite Gallo’s role in confirming HIV as the cause of AIDS, Montagnier and colleagues were the first to isolate the virus.
Prevalence and distribution of HIV/AIDS
According to data published by the World Health Organization (WHO), about 36.7 million people were living with HIV, approximately 1.8 million people were newly infected with HIV, and about 1 million people died of HIV-related causes in 2016. Since 1981 about 35 million people have died from HIV infection. In the early 21st century, however, the annual number of new infections began to decrease, and since about 2005 the annual number of AIDS-related deaths globally has also declined. The latter trend has been largely due to improved access to treatment for the afflicted. Thus, there has been an increase in the overall number of people living with AIDS. Nonetheless, a 2016 United Nations report on AIDS suggested that the decline in annual new infections had plateaued, and disparities in HIV incidence, AIDS-related deaths, and access to treatment were evident within countries and between regions, different age groups, and males and females.
About two-thirds of all infections occur in people living in sub-Saharan Africa, and in some countries of the region the prevalence of HIV infection in the adult population exceeds 10 percent. Rates of infection are lower in other parts of the world, but different subtypes of the virus have spread to Europe, India, South and Southeast Asia, Latin America, and the Caribbean. Rates of infection have leveled off somewhat in the United States and Europe. In the United States more than 1.1 million people are living with HIV/AIDS, and about 44 percent of all new infections are among African Americans. In Asia sharp increases in HIV infection have occurred in China and Indonesia. Access to antiretroviral treatment for AIDS remains limited in some areas of the world, although more people are receiving treatment today than in the past.