HIV PANDEMIC ORIGINS LOCATED, LIKELY TO HAVE EMERGED IN KINSHASA AROUND 1920
The HIV pandemic with
us today is almost certain to have begun its global spread from Kinshasa, the
capital of the Democratic Republic of the Congo (DRC), according to a new study.
An international team,
led by Oxford University and University of Leuven scientists, has reconstructed
the genetic history of the HIV-1 group M pandemic, the event that saw HIV
spread across the African continent and around the world, and concluded that it
originated in Kinshasa. The team's analysis suggests that the common ancestor
of group M is highly likely to have emerged in Kinshasa around 1920 (with 95%
of estimated dates between 1909 and 1930).
HIV is known to have
been transmitted from primates and apes to humans at least 13 times but only
one of these transmission events has led to a human pandemic. It was only with
the event that led to HIV-1 group M that a pandemic occurred, resulting in almost
75 million infections to date. The team's analysis suggests that, between the
1920s and 1950s, a 'perfect storm' of factors, including urban growth, strong
railway links during Belgian colonial rule, and changes to the sex trade,
combined to see HIV emerge from Kinshasa and spread across the globe.
A report of the
research is published in this week's Science.
'Until now most
studies have taken a piecemeal approach to HIV's genetic history, looking at
particular HIV genomes in particular locations,' said Professor Oliver Pybus of
Oxford University's Department of Zoology, a senior author of the paper. '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. It seems a combination of factors in
Kinshasa in the early 20th Century created a 'perfect storm' for the emergence
of HIV, leading to a generalised epidemic with unstoppable momentum that
unrolled across sub-Saharan Africa.'
'Our study required the
development of a statistical framework for reconstructing the spread of viruses
through space and time from their genome sequences,' said Professor Philippe
Lemey of the University of Leuven's Rega Institute, another senior author of
the paper. 'Once the pandemic's spatiotemporal origins were clear they could be
compared with historical data and it became evident that the early spread of
HIV-1 from Kinshasa to other population centres followed predictable patterns.'
One of the factors the
team's analysis suggests was key to the HIV pandemic's origins was the DRC's
transport links, in particular its railways, that made Kinshasa one of the best
connected of all central African cities.
'Data from colonial
archives tells us that by the end of 1940s over one million people were
travelling through Kinshasa on the railways each year,' said Dr Nuno Faria of
Oxford University's Department of Zoology, first author of the paper. 'Our
genetic data tells us that HIV very quickly spread across the Democratic
Republic of the Congo (a country the size of Western Europe), travelling with
people along railways and waterways to reach Mbuji-Mayi and Lubumbashi in the
extreme South and Kisangani in the far North by the end of the 1930s and early
1950s. 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.'
It had been suggested
that demographic growth or genetic differences between HIV-1 group M and other
strains might be major factors in the establishment of the HIV pandemic.
However the team's evidence suggests that, alongside transport, social changes
such as the changing behaviour of sex workers, and public health initiatives
against other diseases that led to the unsafe use of needles may have
contributed to turning HIV into a full-blown epidemic -- supporting ideas
originally put forward by study co-author Jacques Pepin from the Université de
Sherbrooke, Canada.
Professor Oliver Pybus
said: '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. 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.'
The team says that
more research is needed to understand the role different social factors may
have played in the origins of the HIV pandemic; in particular research on
archival specimens to study the origins and evolution of HIV, and research into
the relationship between the spread of Hepatitis C and the use of unsafe
needles as part of public health initiatives may give further insights into the
conditions that helped HIV to spread so widely.
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