China didn't report a death until January 11.
It was identified and named in November, and it was formally announced the last day of December. The WHO definitely knew of the existence of COVID19 by the last day of December at the latest, and likely earlier, and notified countries around that time.
Accounts differ about when the WHO communicated with the United States. I've read New Year's Day and January 3.
https://www.nytimes.com/article/coronavirus-timeline.html
DEC. 31
Chinese authorities treated dozens of cases of pneumonia of unknown cause.
On Dec. 31, the government in Wuhan, China, confirmed that health authorities were treating dozens of cases. Days later, researchers in China identified a new virus that had infected dozens of people in Asia. At the time, there was no evidence that the virus was readily spread by humans. Health officials in China said they were monitoring it to prevent the outbreak from developing into something more severe.
JAN. 11
China reported its first death.
On Jan. 11, Chinese state media reported the first known death from an illness caused by the virus, which had infected dozens of people. The 61-year-old man who died was a regular customer at the market in Wuhan, where the illness is believed to have originated, and he had previously been found to have abdominal tumors and chronic liver disease. The report of his death came just before one of Chinas biggest holidays, when hundreds of millions of people travel across the country.