The origin of the Human Immunodeficiency Virus (HIV) has been a subject of scientific research and debate since the virus was identified in the 1980s. There is now a wealth of evidence on how, when and where HIV first began to cause illness in humans.
HIV is thought to have occurred after people ate chimps that were carrying the Simian Immunodeficiency Virus (SIV).
HIV is a type of lentivirus, which means it attacks the immune system. SIV attacks the immune systems of monkeys and apes in a very similar way. This suggests HIV and SIV are closely related, and that SIV in monkeys and apes crossed over to humans to become HIV.
Studies of some of the earliest known samples of HIV provide clues about when it first appeared in humans and how it evolved. The first verified case of HIV is from a blood sample taken in 1959 from a man who was living in what is now Kinshasa in the Democratic Republic of Congo.
Scientists used this sample to create a 'family-tree' of HIV transmission. By doing this, they were able to trace the first transmission of SIV to HIV in humans, which they concluded took place around 1920, also in Kinshasa. This area is known for having the most genetic diversity in HIV strains in the world, reflecting the number of different times SIV was passed to humans. Many of the first cases of AIDS were recorded there too.
No, there are actually two types of HIV: HIV-1 and HIV-2, and they have slightly different origins.
HIV-1 is closely related to the strain of SIV found in chimps. While HIV-2 is closely related to the strain of SIV found in sooty mangabeys monkeys. The crossover of HIV-2 to humans is believed to have happened in a similar way as HIV-1 (by eating monkey meat).
HIV-2 is far more rare, and less infectious than HIV-1, so it infects far fewer people. It is mainly found in a few West African countries, such as Mali, Mauritania, Nigeria and Sierra Leone.
To complicate things further, HIV is also classified by four main groups of viral strain (M, N, O and P), each of which has different genetic make-up. HIV-1 Group M is the strain that has caused the majority of HIV infections in the world today, meaning it is the dominant strain.
In the 1960s, the 'B' subtype of HIV-1 (which belongs to Group M) made its way to Haiti. This is thought to have happened because many Haitians had been working in the Democratic Republic of Congo and had then returned to Haiti. Initially, Haitians were blamed for starting the HIV epidemic, and suffered severe racism, stigma and discrimination as a result.
Because this is when people first became aware of HIV, and it was when HIV was officially recognised as a new health condition. But HIV had actually been around for decades by then.
In 1981, rare diseases, such as Kaposi's Sarcoma (a rare cancer) and a lung infection called PCP, were being reported among gay men in New York and California. Scientists began to suspect that an unidentified infectious 'disease' was the cause.
At first, the ‘disease’ was called all sorts of names relating to the word ‘gay'. It wasn't until mid-1982 that scientists realised it was also spreading among other populations, such as haemophiliacs and people who inject drugs. In September that year, they named it Acquired Immune Deficiency Syndrome (AIDS).
In 1983, scientists at the Pasteur Institute in France identified the virus linked to AIDS, which they called Lymphadenopathy-Associated Virus (LAV). Scientists at the USA National Cancer Institute confirmed this virus was the cause of AIDS and called it HTLV-III. LAV and HTLV-III were later acknowledged to be the same. A few years later, the virus was renamed as HIV.
You can find out more on this interactive timeline of the history of the HIV pandemic.
