New docs reveal scientists in Wuhan fell ill with Covid-like symptoms in late 2019 - months before the pandemic began to ravage the world.
But now, secretary of state Mike Pompeo has demanded the World Health Organisation launch an investigation into the possibility that Covid was an "accidental" lab leak.
Accusations of a cover-up by the Chinese government have been repeatedly dismissed and pressures for a full investigation into the lab suspected of being the source of coronavirus have so far been resisted.