IIRC, public toilets due to fecal matter were a possible infection vector (I hope I am using the term correctly) [4], which suggests that there had been covid cases since December in Italy as the traces were in waste water [2,3].
Some hypothesise that covid had been circulating in humans long before the market outbreak [5], this hypothesis does seem to corroborate the hypothesis that the virus had long spread before the first 'official' outbreak in Wuhan.
[1] https://www.rfi.fr/en/france/20210311-surprises-about-french...
[2] https://www.independent.co.uk/news/world/europe/coronavirus-...
[3] https://www.bbc.com/news/world-europe-53106444
[4] https://www.forbes.com/sites/jamiegold/2020/06/18/new-scient...
[5] https://www.cbc.ca/radio/quirks/mar-27-covid-pandemic-origin...