'Perfect storm' turned HIV from local to global killer

Almost like detectives retracing the steps of a killer in a our era, researchers have pieced together how the virus that later became known as HIV grew from infecting a few hunter-gatherers in Cameroon to affecting 76 million people across the globe.

Using historic blood samples to create a viral timeline, the team confirms that Kinshasa, the capital of the Democratic Republic of the Congo (DRC), was the springboard for an explosion of infection that began around 1920 – and for the first time, comprehensively map out what happened next.

Once HIV had got a toehold in Kinshasa, migrant workers gradually carried the virus south to mining regions fed by new railways.

Then, after the DRC became independent from Belgium in 1960, the virus spiralled out of control and spread to the rest of southern Africa, decades before the disease was first reported in 1981, and the virus was officially discovered in 1983.

"We think the virus hit a 'perfect storm' of factors that helped it spread," says Oliver Pybus of the University of Oxford, head of the team. "From the virus's point of view, it hit the jackpot."