As the World Health Organisation prepares to send a team into China to investigate the origin of the Covid-19 disease, scientists with experience tracking virus behaviour say the search could take years of work and may not reach a definitive conclusion.
Exactly how, where and when the pathogen got into a human is the unsolved mystery.
The consensus is that Sars-CoV-2, the coronavirus that causes Covid-19, likely came from a bat. It may have found its way into another animal, shifting its genetic shape along the way, enabling it to latch onto human cells. Once in a human host it was carried on trains, buses and planes to infect the world as people breathed it in and coughed it out.
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