The real story is much more global and fiddly. Scientists now know that there are two main types of the human virus: HIV-1 and HIV-2. The most prevalent and most infectious type, HIV-1, is then broken down into groups M, N, O, and P. Group M is the most common group and it’s responsible for 90 percent of HIV-1 infections worldwide. By looking at its genetic building blocks and noting the patterns of mutations, scientists can work backward to figure out its family tree and show how it first emerged in people.
It’s clear that the HIV-1 group M virus settled and spread in the US between 1970 and 1971 after the virus jumped from the Caribbean to New York City, eventually spreading to San Francisco by 1974. HIV emerged in the Caribbean when it was first carried to Haiti in 1967 from the Democratic Republic of the Congo. The oldest known sample of HIV-1 comes from a blood sample collected from a man in 1959 who was living in Léopoldville, now Kinshasa, in the Democratic Republic of the Congo. However, this is simply the earliest sample that has been kept and tested – the story still goes back further.
Recent research has shown that the city of Kinshasa played a huge role in the early spread of HIV from at least 1920 onwards. Over the following 40 years, the virus quietly lurked in this bustling port town, until it met the perfect storm – new technology and colonialism were connecting the world, for better or for worse, while changing social attitudes and prolific prostitution meant that sex was everywhere.
Around this time, a handful of people from outside of sub-Saharan Africa are believed to have contracted the virus. Most notable is Arvid Noe, a Norwegian sailor who traveled to Africa on numerous voyages in the early 1960s. Noe, along with his wife and daughter, died of AIDS complications in 1976, some of the earliest documented HIV/AIDS-related deaths.
The virus had first journeyed to Kinshasa in the 1920s from Cameroon, most likely down through the trade routes of the Sangha River and the Congo River. Here, in the chimp-filled rainforests of Cameroon, it’s believed that the HIV virus was transferred to humans by a non-human primate. We think this because chimp poop from this area contains a mutated form of simian immunodeficiency virus (SIV) that’s suspiciously similar to early forms of HIV.