That is also an issue in working with China on how to mitigate the risks of travel ahead of the Lunar New Year public holiday, which officially runs from Jan. 21, the WHO said.

The holiday was known pre-pandemic as the world's largest annual migration of people.

The WHO also said China is still heavily underreporting deaths from COVID-19, although it is now providing more information on its outbreak.

"There are some very important information gaps that we are working with China to fill," said COVID-19 technical lead, Maria Van Kerkhove.

China says it has been transparent with its COVID-19 data.