The scale of a mysterious pneumonia virus from Wuhan in China might be far larger than previously reported, experts have warned, as various countries stepped up screening measures ahead of the Chinese holiday travel season.
Health officials from the central Chinese city have reported dozens of infections by the new corona-virus but scientists at the MRC Centre for Global Infectious Disease Analysis at Imperial College in London said in a paper published on Friday that the number could be much higher.
The study estimated 1,723 people in Wuhan could be infected as of Jan 12. Given that three Chinese have been discovered abroad with the virus - two Chinese women visiting Thailand and a Chinese man working in Japan - and Wuhan's role as a major travel hub, the scientists believe the spread domestically could also be wider.
The MRC Centre for Global Infectious Disease Analysis advises bodies including the World Health Organisation (WHO).
"The estimates presented here suggest surveillance should be expanded to include all hospitalised cases of pneumonia or severe respiratory disease in the Wuhan area and other well-connected Chinese cities," the scientists wrote in the four-page report.
"I am substantially more concerned than I was a week ago," Professor Neil Ferguson, one of the authors, told the BBC, though he added it was "too early to be alarmist".
Wuhan health officials said yesterday four new cases had been detected. The new patients, all men, fell ill between Jan 5 and 8.
The Wuhan Municipal Health Commission said yesterday it has confirmed 45 cases in the city as of Thursday.
The virus, from the same family that causes Sars and Mers, has so far claimed two lives.
While many of the cases are believed to be linked to the Wuhan Huanan Seafood Wholesale Market, several patients have never been there, suggesting the disease has spread to other parts of the city.
While there is no concrete evidence of the spread between humans, concerns of a pandemic remain.
The Wuhan health authorities said transmission between humans "cannot be ruled out".
The city of 11 million is a major transport hub and hundreds of millions are expected to travel home in the coming days to celebrate the Chinese New Year in the world's largest annual human migration.
China has not announced any travel restrictions, but the authorities in Hong Kong have stepped up detection measures, including rigorous temperature checkpoints for inbound travellers from the Chinese mainland.
Hong Kong's South China Morning Post reported that there are two suspected cases in the neighbouring city of Shenzhen and one in Shanghai. Local authorities have not confirmed the cases.
At Singapore's Changi Airport, passengers arriving from Wuhan are being screened. So far, six suspected cases have been detected, including one yesterday. Five have tested negative for the virus.
The United States on Friday began 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.
Thailand said it was screening passengers arriving in Bangkok, Chiang Mai and Phuket and would soon introduce similar controls in the beach resort of Krabi.
After the second death was reported, there was intense online discussion about the severity of the virus and whether the Chinese government was hiding information from the public.
Several people complained about censorship of online posts, while others made comparisons to 2003 when Beijing drew criticism from the WHO for under-reporting the number of Sars cases. A post on China's social media platform Weibo read: "It's so strange. Japan, Thailand all have Wuhan pneumonia cases but in China we don't have any infections outside of Wuhan?"