Nearly a year and a half since Covid-19 was detected in the Chinese city of Wuhan, the question of how the virus first emerged remains a mystery.
But in recent weeks the controversial claim that the pandemic might have leaked from a Chinese laboratory – once dismissed by many as a fringe conspiracy theory – has been gaining traction.
Now, US President Joe Biden has announced an urgent investigation that will look into the theory as a possible origin of the disease.
So what do we know about the competing theories – and why does the debate matter?
Analysis | Timeline: How the Wuhan lab-leak theory suddenly became credible
The possibility that the coronavirus emerged from a lab was quickly dismissed by scientists in early 2020. This timeline shows which events and scientific publications had an impact on changing minds. washingtonpost.com
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