A team of scientists led by Oxford University in the UK and the University of Leuven in Belgium has reconstructed the genetic history of the HIV-1 group M pandemic, which is the strain that affects the world today.
The research has revealed that the common ancestor of the group M strain originated in Kinshasa, the capital of the Democratic Republic of the Congo, between 1909 and 1930, and also explained some of the circumstances that led to it becoming the pandemic that’s now infected almost 75 million people to date. Their research is published in the journal Science.
“Until now most studies have taken a piecemeal approach to HIV's genetic history, looking at particular HIV genomes in particular locations,” said Oliver Pybus, the senior author of the paper from Oxford University, in a press release.
“For the first time we have analysed all the available evidence using the latest phylogeographic techniques, which enable us to statistically estimate where a virus comes from. This means we can say with a high degree of certainty where and when the HIV pandemic originated.”
Once this origin spot was determined, the scientists were able to compare them to historical data, and confirmed that the spread of HIV-1 from Kinshasa followed a predictable pattern.
But importantly, the scientists also found out what caused the virus to become a pandemic.
HIV actually transferred from monkeys and apes into humans at least 13 times that scientists are aware of of, but only one of these events led to the human pandemic.
Previous theories have suggested that perhaps the HIV-1 group M was genetically different to other HIV strains, or that demographic growth may have played a role in its spread.
But the researchers found that there was in fact a “perfect storm” of factors that led to this particular event triggering the global pandemic we now face - these factors include urban growth, strong railway links across the Democratic Republic of the Congo during Belgium’s rule, public health initiatives that led to the unsafe use of needles and changes to the sex trade.
This caused the virus to spread extremely quickly across the Democratic Republic of Congo - a country the size of Western Europe - and allowed it to spread to other continents.
“This helped establishing early secondary foci of HIV-1 transmission in regions that were well connected to southern and eastern African countries. We think it is likely that the social changes around the independence in 1960 saw the virus 'break out' from small groups of infected people to infect the wider population and eventually the world,” said Nuno Faria, the first author of the paper from Oxford University, in the release.
The team is now further investigating the evolution of the HIV pandemic strain and its relationship with other diseases in order to find further insight into how the virus managed to spread so fast. But they’re confident that they now have a firm understanding of its origins and the unfortunate factors that led to its spread.
“Our research suggests that following the original animal to human transmission of the virus (probably through the hunting or handling of bush meat) there was only a small 'window' during the Belgian colonial era for this particular strain of HIV to emerge and spread into a pandemic,” said Pybus. “By the 1960s transport systems, such as the railways, that enabled the virus to spread vast distances were less active, but by that time the seeds of the pandemic were already sown across Africa and beyond."