The first case of someone in China suffering from Covid-19, the disease caused by the novel coronavirus, can be traced back to November 17, according to government data seen by the South China Morning Post.
Chinese authorities have so far identified at least 266 people who were infected last year, all of whom came under medical surveillance at some point.
Some of the cases were likely backdated after health authorities had tested specimens taken from suspected patients.
Interviews with whistle-blowers from the medical community suggest Chinese doctors only realised they were dealing with a new disease in late December.
Scientists have been trying to map the pattern of the early transmission of Covid-19 since an epidemic was reported in the central China city of Wuhan in January, two months before the outbreak became a global health crisis.