The wet market hypothesis claims the Covid outbreak began in the Wuhan wet market in December 2019.
We now know from analysis of stored patient samples that it was in Italy by October 2019(*) and have inconclusive tests from September 2019 so it may have been there earlier. I also have been told by people working in medicine in North America that they have found positive stored samples from patients in October 2019.
So wherever it came from, it almost certainly did not originate in the wet market in December 2019 and appears to have been worldwide by October 2019. This explains the 'super-duper scary spread' in spring 2020 because it had been going around for months and as soon as they started mass testing they started finding lots of people who tested positive.
(*) And we already had pretty good evidence of this in early 2020 as an Italian virologist had been tracking an unusual respiratory disease through the winter before it suddenly became The Pandemic.
However, this is getting a bit off-topic for railways, unless it spread by rail.