The true scale of the outbreak of a mysterious SARS-like virus in China is likely far bigger than officially reported, scientists have warned, as countries ramp up measures to prevent the disease from spreading.

Fears that the virus will spread are growing ahead of the Lunar New Year holiday, when hundreds of millions of Chinese move around the country and many others host or visit extended family members living overseas.

Authorities in China say two people have died and at least 45 have been infected, with the outbreak centred around a seafood market in the central city of Wuhan, a city of 11 million inhabitants that serves as a major transport hub.

But a paper published Friday by scientists with the MRC Centre for Global Infectious Disease Analysis at Imperial College in London said the number of cases in the city was likely closer to 1,700.

The researchers said their estimate was largely based on the fact that cases had been reported overseas — two in Thailand and one in Japan.

The virus — a new strain of coronavirus that humans can contract — has caused alarm because of its connection to SARS (Severe Acute Respiratory Syndrome), which killed nearly 650 people across mainland China and Hong Kong in 2002-2003.

China has not announced any travel restrictions, but authorities in Hong Kong have already stepped up detection measures, including rigorous temperature checkpoints for inbound travellers from the Chinese mainland.

The US said from Friday it would begin screening flights arriving from Wuhan at San Francisco airport and New York's JFK — which both receive direct flights — as well as Los Angeles, where many flights connect.

And Thailand said it was already screening passengers arriving in Bangkok, Chiang Mai and Phuket and would soon introduce similar controls in the beach resort of Krabi.

– Two deaths –

No human-to-human transmission has been confirmed so far, but Wuhan's health commission has said the possibility "cannot be excluded".

A World Health Organization doctor said it would not be surprising if there was "some limited human-to-human transmission, especially among families who have close contact with one another".

Scientists with the MRC Centre for Global Infectious Disease Analysis — which advises bodies including the World Health Organization — said they estimated a "total of 1,723" people in Wuhan would have been infected as of January 12.

"For Wuhan to have exported three cases to other countries would imply there would have to be many more cases than have been reported," Professor Neil Ferguson, one of the authors of the report, told the BBC.

"I am substantially more concerned than I was a week ago," he said, while adding that it was "too early to be alarmist".

"People should be considering the possibility of substantial human-to-human transmission more seriously than they have so far," he continued, saying it was "unlikely" that animal exposure was the sole source of infection.

Local authorities in Wuhan said a 69-year-old man died on Wednesday, becoming the second fatal case, with the disease causing pulmonary tuberculosis and damage to multiple organ functions.

After the death was reported, online discussion spread in China over the severity of the Wuhan coronavirus — and how much information the government may be hiding from the public.

Several complained about censorship of online posts, while others made comparisons to 2003, when Beijing drew criticism from the WHO for underreporting the number of SARS cases.

"It's so strange," wrote a web user on the social media platform Weibo, citing the overseas cases in Japan and Thailand. "They all have Wuhan pneumonia cases but (in China) we don't have any infections outside of Wuhan — is that scientific?"

Coronavirus: new disease spreading in Asia revives SARS fears
Paris (AFP) Jan 20, 2020 –

A mysterious SARS-like virus has spread around China with more than 200 diagnosed cases in the cities of Wuhan, Beijing and Shenzhen, plus two people infected in Thailand and another case confirmed in Japan. Here are a few key points about coronavirus.

– What is coronavirus? –

The UN's health agency says that the outbreak of the disease in Wuhan is a never-before-seen strain belonging to a broad family of viruses ranging from the common cold to more serious illnesses such as SARS.

According to Arnaud Fontanet, head of the department of epidemiology at Institut Pasteur in Paris, the new strain is the seventh known type of coronavirus that humans can contract.

"We think that the source may have been animals sold at market and from there it passed to the human population," he told AFP.

The World Health Organization (WHO) says an "animal source seems the most likely primary source… with some limited human-to-human transmission occurring between close contacts."

The outbreak has caused alarm because of the link with SARS (Severe Acute Respiratory Syndrome), which killed 349 people in mainland China and another 299 in Hong Kong in 2002-2003.

Fontanet said the current virus strain was 80 percent genetically identical to SARS.

A total of 201 people have now been diagnosed with the virus in China, and the outbreak has already claimed three lives.

– Time to panic? –

Fontanet said that the coronavirus appears to be "weaker" than SARS in its current form, but cautioned that it could mutate into a more virulent strain.

"We don't have evidence that says this virus is going to mutate, but that's what happened with SARS," he said.

"The virus has only been circulating a short time, so it's too early to say."

As for person-to-person transmission — a key hallmark of pandemics — it may also be too early to tell for sure.

But Wuhan authorities said over the weekend that some of the new cases had "no history of contact" with the seafood market believed to be the centre of the outbreak.

Authorities have pronounced the risk of human transmission "weak" but not impossible.

Fontanet said the fact that the virus had spread beyond China, to Japan and Thailand, was "starting to make us fear that interhuman transmission is possible".

Scientists with the MRC Centre for Global Infectious Disease Analysis at Imperial College in London warned in a paper last week that the number of cases in Wuhan was likely to be close to 1,700, much higher than the number officially identified.

WHO has advised that individuals should protect themselves against the virus by thoroughly washing their hands, covering their noses when they sneeze, thoroughly cooking meat and eggs, and avoiding close contact with wild or farm animals.

The best way of containing any disease outbreak is to rapidly confirm the source, according to Raina MacIntyre, from the University of New South Wales in Sydney.

"Tests are being done on animals in the Wuhan region and they should provide some insight," she said.

Experts said authorities must be vigilant and monitor travellers coming to and from Wuhan for signs of breathing problems.

– Lessons learned? –

Fontanet said health workers in China had responded admirably by rapidly carrying out testing among patients and linking the cases to the market in question.

"We've learned some lessons from SARS. We're better armed and more reactive," he said.

Adam Kamradt-Scott, an expert in the spread and control of infectious diseases at the University of Sydney, said China had "has been quick to share the genome sequencing of this novel coronavirus".

"This has enabled the identification of this new case in Japan," he said.

Fontanet said that such transparency was different to the start of the SARS epidemic, when China "hid the story for two or three months" at the start of the outbreak.