HONG KONG — Australian officials said Tuesday that the country would begin screening passengers on flights from Wuhan, the Chinese city where a new coronavirus has infected more than 200 people and killed at least four, as global concern has grown about the spread of the disease.
Adding to worries about the outbreak was confirmation by a prominent Chinese scientist on Monday night that the disease is capable of spreading from person to person. Dr. Zhong Nanshan, a scientist leading a group of experts in examining the outbreak in Wuhan, said the virus could be present in particles of saliva and that in one case, a patient appeared to have infected 14 medical workers.
The number of reported cases in China more than tripled earlier this week as the authorities expanded testing across the country. Most of the cases were found in Wuhan, where the disease was first reported last month.
China’s health commission said Tuesday that 291 cases had been reported nationwide, with 270 in Hubei, the province that includes Wuhan. Major Chinese cities including Beijing, Shanghai and Shenzhen have also reported cases of infections.
Infections have been confirmed abroad in Japan, South Korea and Thailand, all in people who traveled from Wuhan. The World Health Organization said it would hold an emergency meeting on Wednesday to determine whether the outbreak was an international public health emergency.
“It is now very clear from the latest information that there is at least some human-to-human transmission,” said Dr. Takeshi Kasai, the Western Pacific regional director for the World Health Organization.
Dr. Kasai said that the infections among health care workers added to the evidence that the virus was spreading between humans, but more analysis of the data was necessary to understand the full extent of such transmission.
Worries that the outbreak could worsen and hit the Chinese economy sent financial markets down across Asia on Tuesday. The Chinese currency, the renminbi, weakened in value against the American dollar. Stock markets in Europe also opened generally lower.
On Monday, China’s health commission said it would respond with measures intended to manage outbreaks of the most virulent diseases, including mandatory reporting of cases, and classified the virus as a class B infectious disease — a category that includes diseases such as SARS.
The authorities in Wuhan will begin barring group tours from traveling outside of the city and carry out checks of vehicles to search for live animals, state media reported on Monday. The city has also installed infrared thermometers at airports, and bus and train stations.
The potential for the disease to spread across more countries has prompted health authorities to step up checks at their borders.
In Australia, border security and biosecurity staff will meet and screen passengers from three direct flights from Wuhan to Sydney, Brendan Murphy, the government’s chief medical officer, said Tuesday.
Professor Murphy warned, however, that such measures were not foolproof. Some people who are carrying the virus might not show symptoms, he added.
“You cannot absolutely prevent entry into the country of a disease like this,” he said.
Australia is also considering expanding the screening to cover more of the 160 flights that come from China each week.
In the Australian state of Queensland, health officials placed in quarantine a man who had traveled to Wuhan and returned with a respiratory illness.
“The man will remain in isolation until his symptoms have resolved,” the Queensland health department said.
The Centers for Disease Control and Prevention said Friday that the United States would begin screening passengers arriving from Wuhan at airports in New York, San Francisco and Los Angeles.
In Hong Kong, the authorities have reported more than 100 potential infections. So far, none have tested positive for the new coronavirus, and most have been discharged. But the possibility of the illness emerging in the territory remained, Matthew Cheung, the city’s second-highest official, said Tuesday.
High-speed rail passengers will have their temperatures checked on arrival in Hong Kong. Air passengers from Wuhan will be required to declare their health status, and people suspected of having an infection will be “forcibly transferred to public hospital to be treated in isolation,” Mr. Cheung said.
Elaine Yu in Hong Kong and Javier C. Hernández in Wuhan, China, contributed reporting.