Staff sell masks at a Yifeng Pharmacy in Wuhan, Chin, Wednesday, Jan. 22, 2020. Pharmacies in Wuhan are restricting customers to buying one mask at a time amid high demand and worries over an outbreak of a new coronavirus. The number of cases of the new virus has risen over 400 in China and the death toll to 9, Chinese health authorities said Wednesday. (AP Photo/Dake Kang)

BEIJING (AP) — Chinese health authorities urged people in the city of Wuhan to avoid crowds and public gatherings, after warning that a new viral illness that has infected more than 400 people and killed at least nine could spread further.

The appeal came ahead of a World Health Organization meeting in Geneva to determine whether the outbreak should be declared a global health crisis.

The number of new cases has risen sharply in China, the center of the outbreak. There were 440 confirmed cases as of midnight Tuesday in 13 jurisdictions, said Li Bin, deputy director of the National Health Commission. Nine people have died, all in Hubei province, since the outbreak emerged in its provincial capital of Wuhan late last month.

“There has already been human-to-human transmission and infection of medical workers,” Li said at a news conference with health experts. “Evidence has shown that the disease has been transmitted through the respiratory tract and there is the possibility of viral mutation.”

The illness comes from a newly identified type of coronavirus, a family of viruses that can cause the common cold as well as more serious illnesses such as the SARS outbreak that spread from China to more than a dozen countries in 2002-2003 and killed about 800 people.

Authorities in Thailand today confirmed four cases, a Thai national and three Chinese visitors. Japan, South Korea, the United States and Taiwan have all reported one case each. All of the illnesses were of people from Wuhan or who recently traveled there.

“The situation is under control here,” Thai Public Health Minister Anutin Charnvirakul told reporters, saying there are no reports of the infection spreading to others. “We checked all of them: taxi drivers, people who wheeled the wheelchairs for the patients, doctors and nurses who worked around them.”

Macao, a former Portuguese colony that is a semi-autonomous Chinese city, reported one case Wednesday.

In Wuhan, pharmacies were restricting face mask sales because of high demand. Residents said they were not overly worried as long as they took preventive measures.

“As an adult, I am not too worried about the disease,” said Yang Bin, 46. “I think we are more worried about our kids … . It would be unacceptable to the parents if they got sick.”

Medical workers in protective suits could be seen carrying supplies and stretchers into Wuhan Medical Treatment Center, where some of the patients are being treated.