I've embedded the tweet in wikipedia's timeline of events (I've trimmed the events). https://en.wikipedia.org/wiki/Timeline_of_the_2019%E2%80%9320_coronavirus_

I've embedded the tweet in wikipedia's timeline of events (I've trimmed the events). https://en.wikipedia.org/wiki/Timeline_of_the_2019%E2%80%9320_coronavirus_pandemic_in_November_2019_%E2%80%93_January_2020#15_January https://en.wikipedia.org/wiki/Timeline_of_the_2019%E2%80%932... 31 December On 31 December 2019, China contacts the WHO and informs them of "cases of pneumonia of unknown etiology (unknown cause) detected in Wuhan"[37] 2 January On 2 January, 41 admitted hospital patients in Wuhan, China, were confirmed to have contracted (laboratory-confirmed) the 2019-nCoV (Novel coronavirus); 27 (66%) patients had direct exposure to Huanan Seafood Wholesale Market. 6 January On Monday, 6 January, the Wuhan health authorities announced they continued seeking the cause but had so far ruled out influenza, avian influenza, adenovirus, and coronaviruses SARS and MERS as the respiratory pathogen that had infected 59 people as of 5 January.[52] 9 January The WHO confirmed that the novel coronavirus had been isolated from one person who had been hospitalised. 11–12 January In China, more than 700 close contacts of the 41 confirmed cases, including more than 400 healthcare workers, had been monitored, with no new cases reported in China since 5 January.[36][50][63][71] The WHO published initial guidance on travel advice, testing in the laboratory and medical investigation. 14 January World Health Organization (WHO) @WHO Preliminary investigations conducted by the Chinese authorities have found no clear evidence of human-to-human transmission of the novel #coronavirus (2019-nCoV) identified in #Wuhan, #China. 14 January On 14 January, two of the 41 confirmed cases in Wuhan were reported to include a married couple, raising the possibility of human-to-human transmission.[74][75] On 14 January, Maria Van Kerkhove, acting head of WHO's emerging diseases unit said that there had been limited human-to-human transmission of the coronavirus, mainly small clusters in families, adding that "it is very clear right now that we have no sustained human-to-human transmission" 18 January The Wuhan City government held an annual banquet in the Baibuting community celebrating the Chinese New Year with forty thousand families in attendance despite the officials' knowledge of the spread of the Wuhan coronavirus. They shared meals, plates and ate together. 20 January On 20 January, after two medical staff were infected in Guangdong, China announced that the virus was human-to-human transmissible.