How did they know to order more supplies in December?
China reported the new novel strain of the coronavirus to the WHO on December 31. [1] If correct, then this means they were monitoring the news, and reacted immediately, and on the very same day of the fresh report.
It's been widely known outside of China that this a novel SARS-like disease was spreading since December 20th, they just didn't confirm that it was novel until the 31st.
Perhaps this shows that industry experts, with skin in the game, are better at determining the relevant trends than the people and institutions you mention.
China spent more than a week attempting to cover coronavirus up. By the time the Chinese government made a statement the problem was pretty well known among the Wuhan medical community.
China reported the new novel strain of the coronavirus to the WHO on December 31. [1] If correct, then this means they were monitoring the news, and reacted immediately, and on the very same day of the fresh report.
[1] https://www.cdc.gov/mmwr/volumes/69/wr/mm6905e1.htm