A new coronavirus that China announced in late December has killed more than 80 people and infected at least 2,700, with a dozen other countries confirming cases and stepping up protection measures.
Here is a timeline.
On December 31 China alerts the World Health Organization (WHO) to several cases of pneumonia in Wuhan, a port city of 11 million people in Hubei province. The virus is unknown.
Several of those infected worked at the city's Huanan Seafood Wholesale Market, which is shut down on January 1.
As infections rise, Chinese officials on January 5 rule out a return of the SARS virus which also originated in China and killed more than 770 people worldwide in 2002 and 2003.
On January 7 they say the outbreak involves a new virus from the coronavirus family. It is named 2019-nCoV.
China announces its first death on January 11: a man in Wuhan.
Two days later the WHO reports a case in Thailand, the first outside China, a woman who had arrived from the city.
On January 16 Japan reports a case of a man who had visited the city.
The United States, Nepal, France, Australia, Malaysia, Singapore, South Korea, Vietnam and Taiwan confirm cases over the following days.
US health authorities start screening flights arriving from Wuhan.
On January 20 China reports a third death in Wuhan and more than 200 infections, with cases also reported outside Hubei province including in Beijing, Shanghai and Shenzhen.
Human-to-human transmission is "affirmative", a Chinese expert on infectious diseases Zhong Nanshan tells state broadcaster CCTV.
Asian countries introduce mandatory screenings at airports of arrivals from high-risk areas of China.
On January 22 the death toll in China hits 17 with more than 550 infections. European airports step up checks on flights from Wuhan.
The city is placed under effective quarantine on January 23 as air and rail departures are suspended in an effort to contain the spread of the virus.
Public transport is halted in at least 18 other cities in Hubei province, affecting tens of millions of people.
Beijing cancels events for the Lunar New Year starting January 25, while officials report the first death outside of Hubei.
The WHO says on January 23 the outbreak does not constitute a global emergency and there is "no evidence" at the moment of the virus spreading between humans outside of China.
On January 24 Shanghai Disneyland closes and Beijing says a section of the Great Wall and other famous landmarks will also be shut.
Hong Kong's Disneyland shuts its doors on January 26.
The United States says it will evacuate its citizens trapped in Wuhan; France and Japan plan similar measures.
On January 27 Mongolia closes its border with China and shuts schools and universities. Malaysia bans visitors from Wuhan.
Beijing extends the Lunar New Year holiday for three days to limit population flows.
© 2020 AFP