The death toll from the outbreak has now topped 100, with more than 4,500 cases in mainland China.

Authorities in Hubei, the Chinese province at the center of the outbreak, earlier said an additional 1,300 cases had been confirmed, bringing the total in the region to over 2,700.

The majority of those are still in hospital, with more than 125 in critical condition. Between Sunday and Monday, there was a 65% jump in the number of reported cases in mainland China, from around 2,700 to over 4,500.

On Monday, the US Centers for Disease Control (CDC) issued a level 3 alert warning against "all nonessential travel to China" -- its highest alert on a scale of 1 to 3.