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.'