The number of people infected with a new virus in China tripled over the weekend, with the outbreak spreading from Wuhan to other major cities.
China's National Health Commission confirmed that the virus, which causes a type of pneumonia, can pass from person-to-person, the official Xinhua News Agency said.
Xinhua reported Zhong Nanshan, a respiratory expert and head of the health commission team investigating the outbreak, confirmed that two cases in China's Guangdong Province were due to human-to-human transmission.
The official news agency said some medical staff had been infected.
There are now more than 200 cases, mostly in Wuhan, though the respiratory illness has also been detected in Beijing, Shanghai and Shenzhen.
Three people have died. Japan, Thailand and South Korea have reported cases.
The sharp rise comes as millions of Chinese prepare to travel for the Lunar New Year holidays.
The virus belongs to the same family of coronaviruses as Severe Acute Respiratory Syndrome (SARS), which killed nearly 800 people globally during a 2002/03 outbreak that also started in China.
Although the outbreak is believed to have originated from a market, officials and scientists are yet to determine exactly how it has been spreading.
Authorities in Wuhan, a central Chinese city of 11 million that has been at the heart of the outbreak, on Monday said 136 new cases had been confirmed over the weekend, with a third person dying of the virus. There had previously been only 62 confirmed cases in the city.
As of late Sunday, officials said 170 people in Wuhan were still being treated in hospital, including nine in critical condition.
Beijing also confirmed its first cases, with five people infected. Shanghai confirmed its first case on Monday - a 56-year-old woman who came from Wuhan.
In the city of Shenzhen, a major tech hub close to Hong Kong, officials said a 66-year-old man showed symptoms of the virus following a trip to visit relatives in Wuhan.
State media reported 14 other cases in Guangdong province.
Four cases have been confirmed abroad - two in Thailand, one in Japan and one in South Korea - all of them involving people who are either from Wuhan or have visited the city.
The World Health Organization said it was currently not recommending restrictions on travel or trade, but was providing guidance to countries preparing for any outbreak.
Airports in Singapore, Hong Kong and the Japanese capital Tokyo have been screening air passengers from Wuhan, and US authorities last week announced similar measures at three major airports in San Francisco, Los Angeles and New York.
What we know about the virus
Source: World Health Organization
2019-nCoV, as it's been labelled, is understood to be a new strain of coronavirus that has not previously been identified in humans
Coronaviruses are a broad family of viruses, but only six (the new one would make it seven) are known to infect people
Scientists believe an animal source is "the most likely primary source" but that some human-to-human transmission has occurred
Signs of infection include respiratory symptoms, fever, cough, shortness of breath and breathing difficulties
People are being advised to avoid "unprotected" contact with live animals, thoroughly cook meat and eggs, and avoid close contact with anyone with cold or flu-like symptoms
What are the Chinese authorities saying?
How China is responding to the outbreak is under close scrutiny, given that it was widely criticised for initially covering up the Sars crisis in late 2002 and early 2003.
On Monday, Chinese President Xi Jinping for the first time publicly addressed the outbreak, saying that the virus must be "resolutely contained".
The foreign ministry, meanwhile, said China was providing "timely information about the disease" and would "work with all parties to deal with the virus".
What impact could Lunar New Year have?
From Friday, most Chinese will begin their week-long Lunar New Year holidays.
It's a time when hundreds of millions travel around China to visit family, raising fears that authorities will not be able to adequately monitor further spread of the disease.
Wuhan is a transport hub and authorities there have for nearly a week been using temperature scanners at airports, and train and bus stations. Those showing signs of fever have been registered, given masks and taken to hospitals and clinics.
Authorities say they will now also be screening everyone leaving the city.
- BBC / Reuters