The virus originated in the central Chinese city of Wuhan in Hubei late last year and has spread to Chinese cities including Beijing and Shanghai, as well as the US, Thailand, South Korea and Japan.
Countries around the world are scrambling to contain the spread of a deadly coronavirus that has sent shockwaves of concern around the globe.
The death toll in China's viral outbreak has risen to 25, with the number of confirmed cases also leaping to 830, the national health commission said on Friday.
The body said authorities also were examining 1,072 suspected cases of the virus.
The outbreak has prompted China to effectively quarantine some 20 million people, but the World Health Organization said Thursday that the disease did not yet constitute a global health emergency.
Japan's health ministry said Friday it had confirmed the country's second case of a novel coronavirus strain, in a man who travelled from the Chinese city of Wuhan.
In a statement, the ministry said the man in his 40s was a resident of the Chinese city where the outbreak began and arrived in Japan on January 19.
He reported having had a fever for several days before his arrival but said that his condition had stabilised by the time of his arrival in Japan.
On January 22, he reported a fever and he is now in a Tokyo hospital receiving treatment, the ministry said.
The statement added that the man denied having visited the market in Wuhan identified as the source of the outbreak, and said he had worn a medical mask while travelling.
The case was confirmed just over a week after Japanese authorities reported the country's first incidence of the new virus that has killed 18 and infected hundreds of others.
The coronavirus family includes the common cold as well as viruses that cause more serious illnesses, such as the SARS (Severe Acute Respiratory Syndrome) outbreak that spread from China to more than a dozen countries in 2002-03 and killed about 800 people, and Middle Eastern respiratory syndrome, or MERS, which is thought to have originated from camels.
China in lockdown
Chinese authorities Thursday moved to lock down at least three cities with a combined population of more than 18 million in an unprecedented effort to contain the deadly new virus that has sickened hundreds of people and spread to other parts of the world during the busy Lunar New Year travel period.
The open-ended lockdowns are unmatched in size, embracing more people than New York City, Los Angeles and Chicago put together.
The train station and airport in Wuhan, the epicentre of the outbreak, were shut down, and ferry, subway and bus service was halted. Normally bustling streets, shopping malls, restaurants and other public spaces in the city of 11 million were eerily quiet. Police checked all incoming vehicles but did not close off the roads.
Authorities announced similar measures would take effect Friday in the nearby cities of Huanggang and Ezhou. In Huanggang, theatres, internet cafes and other entertainment centres were also ordered closed.
In the capital, Beijing, officials canceled major events indefinitely, including traditional temple fairs that are a staple of holiday celebrations, to help control the spread of the virus. The Forbidden City, the palace complex in Beijing that is now a museum, announced it will close indefinitely on Saturday.
At least 17 people have died in the outbreak, all of them in and around Wuhan. Close to 600 have been infected, the vast majority of them in Wuhan, and many countries have begun screening travellers from China for symptoms of the virus, which can cause fever, coughing, trouble breathing and pneumonia.
Chinese officials have not said how long the shutdowns will last. While sweeping measures are typical of China's communist government, large-scale quarantines are rare around the world, even in deadly epidemics, because of concerns about infringing on people's liberties. And the effectiveness of such measures is unclear.
“To my knowledge, trying to contain a city of 11 million people is new to science," said Gauden Galea, the WHO's representative in China. “It has not been tried before as a public health measure. We cannot at this stage say it will or it will not work."
Jonathan Ball, a professor of virology at molecular virology at the University of Nottingham in Britain, said the lockdowns appear to be justified scientifically.
“Until there's a better understanding of what the situation is, I think it's not an unreasonable thing to do,” he said. “Anything that limits people's travels during an outbreak would obviously work.”
But Ball cautioned that any such quarantine should be strictly time-limited. He added: “You have to make sure you communicate effectively about why this is being done. Otherwise you will lose the goodwill of the people.”
During the devastating West Africa Ebola outbreak in 2014, Sierra Leone imposed a national three-day quarantine as health workers went door to door, searching for hidden cases.
Burial teams collecting corpses and people taking the sick to Ebola centres were the only ones allowed to move freely. Frustrated residents complained of food shortages.
In China, the illnesses from the newly identified coronavirus first appeared last month in Wuhan, an industrial and transportation hub in central China's Hubei province. Other cases have been turned up in the United States, Japan, South Korea and Thailand. Singapore, Vietnam and Hong Kong reported their first cases Thursday.
Most of the illnesses outside China involve people who were from Wuhan or had recently travelled there.
Images from Wuhan showed long lines and empty shelves at supermarkets, as people stocked up for what could be weeks of isolation. That appeared to be an over-reaction, since no restrictions were placed on trucks carrying supplies into the city, although many Chinese have strong memories of shortages in the years before the country's recent economic boom.
Local authorities in Wuhan demanded all residents wear masks in public places. Police, SWAT teams and paramilitary troops guarded Wuhan's train station.
The sharp rise in illnesses comes as millions of Chinese travel for the Lunar New Year, one of the world's largest annual migrations of people. Chinese are expected to take an estimated 3 billion trips during the 40-day spike in travel.
Cases will continue to multiply - analysts
Analysts predicted cases will continue to multiply, although the jump in numbers is also attributable in part to increased monitoring.
“Even if (cases) are in the thousands, this would not surprise us," the WHO's Galea said, adding, however, that the number of infected is not an indicator of the outbreak's severity so long as the death rate remains low.
China is keen to avoid repeating mistakes with its handling of SARS. For months, even after the illness had spread around the world, China parked patients in hotels and drove them around in ambulances to conceal the true number of cases and avoid WHO experts. This time, China has been credited with sharing information rapidly, and President Xi Jinping has emphasised that as a priority.
Health authorities are taking extraordinary measures to prevent the spread of the virus, placing those believed infected in plastic tubes and wheeled boxes, with air passed through filters.
How the virus transmitted?
The first cases in the Wuhan outbreak were connected to people who worked at or visited a seafood market, now closed for an investigation. Experts suspect that the virus was first transmitted from wild animals but that it may also be mutating. Mutations can make it deadlier or more contagious.
WHO defines a global emergency as an “extraordinary event” that constitutes a risk to other countries and requires a coordinated international response. Global emergencies were declared over the Zika virus in the Americas, the swine flu pandemic and polio.
Countries typically resist the notion that they have a crisis within their borders and may argue strenuously for other control measures.
Gulf on high-alert
Gulf airports, including one of the world's biggest aviation hubs, said Thursday they would screen all passengers arriving from China amid the outbreak of a deadly virus.
The move goes further than other major transport hubs in Europe and the United States, which have limited their screening to passengers coming from Wuhan, the city at the centre of the scare.
Dubai airport authorities confirmed that "all passengers arriving on direct flights from the People's Republic of China must receive thermal screening at the gate upon arrival," a statement said.
Dubai International Airport in 2018 served over 89 million passengers, including more foreign passengers than any other airport worldwide for the fifth year in a row.
Dubai's government said Thursday that some 989,000 Chinese tourists visited the glitzy emirate last year -- a number expected to cross the one million mark in 2020.
Some 3.6 million Chinese transited through the emirate's main air port in 2019.
The coronavirus has caused alarm because of its similarity to SARS, which killed nearly 650 people across mainland China and Hong Kong in 2002-2003.
Like SARS, it can be passed among humans via the respiratory tract.
The UAE's Abu Dhabi International Airport, another major hub, announced on Twitter Thursday that it had also begun screening passengers arriving fro m China, "in an effort to ensure the health and safety of all of our travellers".
Between them, the two Emirati hubs operate dozens of flights a week with Chinese cities.
China is the UAE's top trading partner and Abu Dhabi is among the 15 top crude oil suppliers to Beijing. Several hundred Chinese companies have offices in the UAE.
Saudi Arabia's pro-government Okaz newspaper reported that the kingdom would also conduct "health assessments" of passengers coming from China.
Shortly after, Kuwait and Bahrain followed suit.
WHO holds off on emergency
The US Centers for Disease Control and Prevention said on Thursday it is seeking special emergency authorisation from the Food and Drug Administration to allow US states to use a CDC-developed diagnostic test to detect the new coronavirus from China.
Currently, states with suspected cases of the new virus must send samples to the CDC for confirmation, as was the case with the US resident in Washington state who was infected while visiting Wuhan, China, the epicentre of the outbreak.
Emergency Use Authorization from the FDA would allow states to use the CDC's test, according to CDC spokesman Benjamin Haynes.
At least 16 people had close contact with the Washington state man diagnosed with the first US case of the virus. None of them so far have shown signs of the virus, according to local health officials.
The World Health Organization on Thursday stopped short of declaring the new virus a global health emergency.