China's National Health Commission says 440 people in 13 Chinese provinces are now infected with the new coronavirus, with nine people dying — and there is evidence of respiratory transmission from patient to patient.

Key points: Chinese authorities say the outbreak can spread through human contact

Chinese authorities say the outbreak can spread through human contact The coronavirus strain is believed to have started in a Chinese seafood market

The coronavirus strain is believed to have started in a Chinese seafood market Hong Kong's Cathay Pacific flight attendants are asking to wear masks on flights

The number of confirmed cases as of Tuesday (local time) marks a rise from the more than 300 previously reported.

Chinese officials said the new virus was also adapting and mutating, underscoring the challenges for health authorities in controlling the outbreak.

An official from the country's Centre for Disease Control and Prevention said the coronavirus originated from a market dealing in illegal wildlife transactions.

The virus, which started in the city of Wuhan at the end of last year, has spread to Beijing and Shanghai, as well as overseas to the United States, Thailand, South Korea, Japan and Taiwan.

The Chinese special administrative region of Macau also confirmed its first case of pneumonia linked to the outbreak, state-owned news agency Xinhua said.

China is taking more strict measures in hospitals to protect healthcare workers from the outbreak, and will increase training for healthcare workers nationwide, officials from the health commission said.

Authorities added that infection of medical staff in the outbreak showed there were loopholes in treatment methods as authorities were still learning about the new virus.

Chinese residents vented their frustrations on social media over the limited availability of face masks being available to purchase in many cities such as Chengdu, as well as online.

Hong Kong confirms first case

A sign at a local pharmacy in the city of Chengdu says all facial masks are sold out. ( Weibo: Chengdu News )

Hong Kong confirmed its first case of the new coronavirus strain on Wednesday, local broadcasters RTHK, Cable TV and TVB said.

The infected patient arrived in Hong Kong via high-speed railway from the mainland, and has been quarantined at the Queen Elizabeth hospital, the reports said.

The Hospital Authority enhanced laboratory surveillance for pneumonia cases to include patients with travel history to all of mainland China.

Hong Kong had deployed temperature-screening machinery at the airport and the high-speed rail station.

Coronavirus spreads to the US and Thailand

Earlier today, a United States man from Washington state who recently travelled to China was diagnosed with the coronavirus, becoming the first confirmed US case of the newly identified illness.

The patient, identified only as a man in his 30s who recently returned from his hometown in China, fell ill over the weekend and was diagnosed with the coronavirus on Monday (local time), Washington Governor Jay Inslee told reporters at a press conference in the United States city of Seattle.

He was in a satisfactory condition at Providence Regional Medical Centre in Washington and was not known to have infected anyone else, Mr Inslee said.

"This is not a moment of high anxiety," Mr Inslee said

"This is a low risk. It appears to have a transmission vector that really should not prevent anyone from going anywhere in Snohomish County [in Washington], except maybe the isolation ward at the hospital."

Last week, the World Health Organisation said there was limited human-to-human transmission, and the global community would be prepared if an outbreak occurred, however authorities now say the virus can spread through human contact.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 1 minute 24 seconds 1 m 24 s Death toll from Wuhan coronavirus rises to nine

The coronavirus, which causes respiratory symptoms similar to a cold or flu, has been linked to a seafood market in Wuhan, the largest city in central China with a population of about 11 million. That market has since been shut down.

The disease has spread to other parts of China, including the capital Beijing where there have been five cases. People have also been diagnosed in Thailand, South Korea, Japan and Taiwan.

The US Centres for Disease Control (CDC) and Washington State said the agency was preparing for more US cases of the coronavirus to emerge, and the CDC raised its travel alert for Wuhan to a level 2, calling for enhanced precautions.

Under that alert level, the CDC recommends people travelling to Wuhan to avoid contact with sick people, animals and animal markets.

The agency said it had developed a new test that allowed it to identify the presence of the virus in a traveller.

A CDC medical officer said all travellers from Wuhan would be redirected to five US airports in Los Angeles, New York, Chicago, Atlanta and San Francisco for screening.

Airline crews fear being infected

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 23 seconds 23 s Footage circulating on Chinese social media shows medics checking the temperature of passengers on a Wuhan to Macau flight.

The flight attendants union at Hong Kong's Cathay Pacific Airways said it has asked the airline to let crew wear face masks on all flights to mitigate the risk of staff catching the new coronavirus.

The coronavirus struck as millions of Chinese prepared to travel for the Lunar New Year, heightening contagion risks and posing a fresh threat to the airline, which has been battered by months of sometimes violent anti-government protests in Hong Kong.

The Cathay Pacific Airways Flight Attendants Union said it had received a "tremendous" amount of emails and messages from members concerned about catching the virus given they were exposed to more than 300 passengers from numerous places on a single flight.

"All of them are worried about the risk they are taking every time they go to work," the union said on its Facebook page on Tuesday (local time).

"It is time for the company to properly address their concerns and allow cabin crew to wear masks on all flights."

The new coronavirus strain has been linked to a seafood market in Wuhan, the largest city in central China.

So far, it said, the airline was not allowing cabin crew to wear masks except on flights to and from Wuhan.

Cathay did not respond immediately to a request for comment.

Cathay told the South China Morning Post, which first reported on the issue, that as required by Hong Kong health authorities, it was distributing health declaration forms and making face masks and antiseptic wipes available at the boarding gate to passengers travelling from Wuhan to Hong Kong.

Financial Services analysts from Jefferies said shares in Cathay and mainland Chinese carriers could remain under pressure for some time if the coronavirus situation became similar to the 2003 SARS outbreak and cases continued to increase. That coronavirus outbreak killed nearly 800 people.

Britain's Heathrow Airport would introduce separate areas for passengers travelling from regions that had been affected by the new flu-like coronavirus in China, Transport Minister Grant Shapps said on Wednesday.

"That is something which we are keeping a very close eye on," Mr Shapps told Sky News.

"There's been some announcements this morning about flights that come direct from the infected region to Heathrow with some additional measures there. This is to ensure that when flights come in directly to Heathrow there is a separate area for people to arrive in."

Reuters/ABC