The scale of the crisis begins to emerge by the 21st January, and on 23rd January The Guardian provides the timeline:
31st December: World Health Organization (WHO) is alerted by the Chinese authorities of a string of pneumonia-like cases in Wuhan. The source of the outbreak has been identified as a wet market.
9th January: The WHO says the outbreak in Wuhan was caused by a previously unknown type of coronavirus.
11th January: Chinese health authorities report the first fatality in Wuhan. They revise downwards the number of sick people to 41.
15th January: China’s health commission says it cannot confirm human-to-human transmission of the virus but the possibility “cannot be excluded”. The next day a first case of the virus is confirmed in Japan in someone who had stayed in Wuhan in early January.
17th January: A second person dies in Wuhan.
20th January: A third death and more than 100 new cases are announced in China. Human-to-human transmission is “affirmative”, a top Chinese expert on infectious diseases, Zhong Nanshan, tells state broadcaster CCTV.