Aids byname and acronym of acquired immunodeficiency syndrome

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.
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The origin of HIV

Details of the origin of HIV remain unclear. However, a lentivirus that is genetically similar to HIV has been found in chimpanzees and gorillas in western equatorial Africa. That virus is known as simian immunodeficiency virus (SIV), and it was once widely thought to be harmless in chimpanzees. However, in 2009 a team of researchers investigating chimpanzee populations in Africa found that SIV in fact causes AIDS-like illness in the animals. SIV-infected chimpanzees have a death rate that is 10 to 16 times higher than their uninfected counterparts. The practice of hunting, butchering, and eating the meat of chimpanzees may have allowed transmission of the virus to humans, probably in the late 19th or early 20th century. The strain of SIV found in gorillas is known as SIVgor, and it is distinct from the strain found in chimpanzees. Because primates are suspected of being the source of HIV, AIDS is considered a zoonosis, an infection that is shared by humans and other vertebrate animals.
Genetic studies of a pandemic strain of HIV, known as HIV-1 group M, have indicated that the virus emerged between 1884 and 1924 in central and western Africa. Researchers estimate that that strain of the virus began spreading throughout those areas in the late 1950s. Later, in the mid-1960s, an evolved strain called HIV-1 group M subtype B spread from Africa to Haiti. In Haiti that subtype acquired unique characteristics, presumably through the process of genetic recombination. Sometime between 1969 and 1972, the virus migrated from Haiti to the United States. The virus spread within the United States for about a decade before it was discovered in the early 1980s. The worldwide spread of HIV-1 was likely facilitated by several factors, including increasing urbanization and long-distance travel in Africa, international travel, changing sexual mores, and intravenous drug use.