Coronavirus origins: the debate flares up, but the evidence remains weak

Nearly three years since SARS-CoV-2 first emerged, we’re still not certain where the virus behind COVID-19 came from.

The location of the initial outbreak close to the Wuhan Institute of Virology drew suspicion that it may have been a lab leak. But scientists largely came out in favour of a natural spillover from bats to humans, through an intermediate animal host, at the Huanan seafood market located a few kilometres away. To date, though, no immediate ancestor of SARS-CoV-2 has been found in bats nor in any other animal that was on sale at the market.

A recent preprint (a study yet to be peer-reviewed) claims to have identified possibly unusual sequence patterns in the SARS-CoV-2 genome. These patterns may indicate the virus was genetically modified in a lab.