The disease first emerged in the city of Wuhan towards the end of last year - but much is yet to be discovered about the mechanism by which it did so. Last week a 57-year-old trader at Huanan seafood market was tentatively identified as the first person there to contract the illness, on December 10. However, she suggested she did so by using toilet facilities shared with wild meat sellers, meaning the search for Patient Zero - the first person infected after COVID-19 jumped species - continues.