HIV, the virus that causes AIDS, probably came into the US from Haiti around the year 1969, a decade earlier than most scientists believed, says new research from the US.
The study is due to be published this week in the Early Online issue of the Proceedings of the National Academy of Sciences and is the work of Michael Worobey, an assistant professor of ecology and evolutionary biology at The University of Arizona in Tucson, and colleagues. The title of the study is “The emergence of HIV/AIDS in the Americas and beyond”.
“Our results show that the strain of virus that spawned the US AIDS epidemic probably arrived in or around 1969. That is earlier than a lot of people had imagined,” said Worobey in a prepared statement.
“Haiti was the stepping stone the virus took when it left central Africa and started its sweep around the world. Once the virus got to the US, then it just moved explosively around the world,” added Worobey.
The researchers found that most HIV/AIDS strains in the US came from a single common ancestor that predates the well storied “Patient Zero” theory. The Patient Zero theory came from a misrepresentation for Patient O (Oh), for “Out of California”, where early research on AIDS by the US Centers for Disease Control and Prevention (CDC) suggested HIV in the US spread in the late 1970s, early 1980s from one man in California.
According to the work of Worobey and colleagues, the strain that came to the US in 1969 was HIV-1 group M subtype B and is the first discovered human immunodeficiency virus. This strain is the most dominant of the AIDS strains that exist in most countries outside of sub-Saharan Africa, nearly all of which descended from the one that came out of Haiti, said the researchers.
Worobey and colleagues analysed the genes in stored blood samples of five AIDS patients to pinpoint the date HIV arrived in the US. All the patients had recently emigrated from Haiti. Using these samples and those of 117 AIDS patients from around the world who were also infected with subtype B, they constructed a family tree of HIV genes.
First they analysed the gene sequences and then using Bayesian statistics they sifted through all possible HIV family trees to find the ones that most closely matched the sequences they found.
The likelihood that the virus went from Africa directly to the US was practically zero, a probability of 0.003.
The most likely route was Africa to Haiti then the US, which yielded a probability of 99.8 per cent.
The gene sequence analysis also showed that most viruses in the US can be traced to one ancestor, the one that entered the US from Haiti in and around 1969.
Worobey and colleagues found that Haiti had a greater genetic diversity of the subtype B virus than the US, Australia, Europe and other countries. They estimated the virus travelled from Africa to Haiti in 1966.
Establishing the genetic diversity of the virus within the subtype B could help develop vaccines against HIV fur use in Haiti said the researchers. This research explained why there was such a large variation of the virus in Haiti, it had “simply been there longer”, they said.
Worobey said the next thing he and his colleagues plan to do is trace the ancestry of HIV back even further, using older archived blood samples.
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Written by: Catharine Paddock