The first case of a curious syndrome of opportunistic infections that is now known as AIDS was recognized in the United States in the early 1980s. In the time since then, the cause of the immune deficiency has been identified as the lentivirus HIV and millions of people have contracted the disease, with a large proportion succumbing within years of infection. Since the first cases, scientists have scrambled to identify where the virus came from, soon finding a similar disease in monkeys, called SIV. If HIV came from African monkeys, how and when did it get to the United States?
The Ancestry of HIV
The human immunodeficiency virus, or HIV, mutates at a rapid rate. Similar to other retroviruses, the family to which lentiviruses belong, the HIV genome is made of RNA. Analyzing the genetic composition of the HIV genome is allowing researchers to establish a timeline of its mutation and trace its origins from SIV. The most recent common ancestor of SIV strains in chimpanzees has been pegged to have originated before the discovery of the new world (c. 1400). There are two strains of HIV, HIV-1 and HIV-2, with HIV-1 being the common strain referred to when someone talks about HIV. HIV-1 is much more widely studied than HIV-2; chimpanzees serve as the reservoir for HIV-1.
Early studies suggested that HIV first entered the human population in central Africa around 1930, most likely from slaughtered chimpanzees. Eating bushmeat, which are slaughtered wild animals sold in villages and some larger cities in underdeveloped nations, has been a common route for the spread of new diseases. The oldest known HIV infection occurred in 1959. The likely sequence of events was SIV mutation to infect humans and subsequent infection, followed by mutation to cause disease as HIV.
Analyzing the HIV Lineage
In November of 2007, new information about the origins of HIV infection in the United States was published in the Proceedings of the National Academy of Sciences (PNAS) by a group including the Department of Ecology and Evolutionary Biology at the University of Arizona and researchers at the University of Miami. The research group conducted genetic analysis on blood samples from early AIDS patients stored by the government (five from Haitian immigrants in 1982 and 1983, and 117 other AIDS patients worldwide), ruling out the possibility that HIV came directly to the United States from Africa.
Haiti was found to be likely be a link between the spread of HIV from Africa, with a 99.8% probability. This particular path had long been debated by researchers. The study found that, around 1966, HIV was brought from central Africa to Haiti. As early as 1979, Haitian immigrants in Miami were reported to suffer from a mystery illness, which is now considered to be AIDS, likely due to a single infected immigrant that arrived in the United States in 1969.
The Timeline of HIV
- 1930 - SIV jumps species in central Africa
- 1959 – Oldest known HIV-1 infection
- 1966 - HIV spreads from Africa to Haiti
- 1969 - HIV spreads from Haiti to the United States
- 1981 – The final stage of HIV infection, AIDS, is recognized as a disease by scientists in the United States
References:
Gilbert et al. The emergence of HIV/AIDS in the Americas and beyond. PNAS, 2007.
Worobey et al. Direct evidence of extensive diversity of HIV-1 in Kinshasa by 1960. Nature, 2008.
Wertheim and Worobey. Dating the age of the SIV lineages that gave rise to HIV-1 and HIV-2. PLoS Computational Biology, 2009.
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