Health authorities in China say 81 people are now dead after being infected with the new coronavirus. Confirmed cases have jumped to more than 2,700.
The authorities say that the virus is becoming more contagious. They say patients with mild symptoms may not know they're infected, making it harder to stop the spread.
So far, cases have been reported in 13 other countries and territories.
Chinese Premier Li Keqiang is visiting Wuhan, the city at the center of the outbreak in a sign of how seriously Beijing is taking the matter.
Li inspected the ongoing containment efforts in the city. He also visited patients, and medical staff on the frontlines of the outbreak.
Authorities are rushing to build a special hospital in Wuhan. Chinese media say a second facility is also being built. The facilities designed for 2000 patients are scheduled for completion in early February.
Beijing is increasing measures to contain the outbreak after locking down a number of cities, including Wuhan. The Lunar New Year holiday is being extended to February 2, which will delay the reopening of schools.
Group tours have been banned from leaving China. Major tourist sites are closing and long-distance bus services stopped.
NHK spoke to a Japanese medical trainee in Wuhan by phone, on a condition of anonymity.
He said infections may be much higher than reported.
"People weren't alarmed about the virus in the beginning. I think nobody expected it could spread this fast."
He also said that around January 3, he heard that health care personnel may have been infected. Chinese media took more than two weeks to report that they had contracted the virus.