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."
|