The deadly new coronavirus outbreak that started in the mainland Chinese city of Wuhan has entered the stage of transmission among families and hospitals, taking it a step closer to a full-blown community epidemic, a top Hong Kong expert warned on Tuesday.
The warning came as a study by the University of Hong Kong (HKU) estimated that the virus had already spread to 20 other mainland cities from Wuhan in Hubei province between January 1 and 17, suggesting the situation was worse than officially reported.
Professor Yuen Kwok-yung, a top infectious diseases expert at HKU, said the transmission of the coronavirus had entered its "third wave".
"Now we can see infections of family members and in hospitals. What we are worried most about is a large outbreak in the community that may cause a situation like what we experienced during Sars," Yuen said, referring to the severe acute respiratory syndrome pandemic of 2002-03.
"We are worried that the super-spreading event might have occurred already … we need to see if sustained human-to-human transmission has happened."
The renowned microbiologist, just back in Hong Kong after a fact-finding trip to Wuhan, called for more measures to tackle the ballooning crisis and curb the spread of the virus.
He advised Hongkongers not to travel to Wuhan unless absolutely necessary.
As of Tuesday night, more than 300 cases of the newly discovered virus had been officially confirmed on the mainland. Of those, 270 were from Hubei province and more than 30 were reported in other parts of the country, including Beijing, Shanghai, Tianjin and Guangdong province, which neighbours Hong Kong.
The virus has spread to Thailand, Japan, South Korea and now Taiwan, which have reported five cases in total. Wuhan has reported six deaths so far.
The crisis could not have come at a worse time, as the Lunar New Year holiday sees the biggest mass migration of people on the planet, with hundreds of millions of Chinese workers in cities returning to their rural homes.
Hong Kong added 12 more suspected infections to its tally in the 24 hours until Tuesday noon, bringing the total to 118 since December 31.
Hospital Authority director of quality and safety Dr Chung Kin-lai said extra measures had been decided on Tuesday to address the threat. Pneumonia patients admitted to hospital who had been to the mainland over the past 14 days would be tested for the new coronavirus, he said.
A model developed by HKU's infectious disease experts estimated the virus would have spread across swathes of mainland China between January 1 and 17.
The analysis, by the university's World Health Organisation Collaborating Centre for Infectious Disease Epidemiology and Control, used travel and other data to map out the likely spread of the virus.
It estimated 1,343 people had been infected in Wuhan, and another 116 in 20 other Chinese cities.
Hong Kong, with no confirmed cases, was not among the affected cities, according to the study.
Researchers at Imperial College London had also previously estimated that 1,723 people in Wuhan had been infected.
The medical centre at HKU also predicted at least 10 new cases would surface in five major cities across the mainland by January 31, the seventh day of the Lunar New Year.
The relatively conservative estimate for Beijing, Shanghai, Chongqing, Guangzhou and Shenzhen was based on several assumptions: that the force of infection would be reduced by 75 per cent with effective preventive measures; that Wuhan was the only source of the outbreak; and there was no super-spreading of the virus with single patients transmitting the virus to an unusually large number of people.
Professor Gabriel Leung, founding director of HKU's infectious disease centre, said health authorities could use its figures to check whether they were identifying all the cases in their jurisdictions.
"If you were the local health authorities in any of these places, these are the numbers you would be expecting to confirm in your tests," he said.
Leung's team worked out the estimated number of cases in Wuhan based on the cases exported overseas. That was then used to predict the number of cases that had spread from ground zero to other parts of China.
Factors taken into account included the number of travellers by air, train and road from Wuhan to other mainland cities during the mass movement of people for the Lunar New Year in 2019 and projections for this year between January 10 and February 18.
Leung urged the public not to panic but advised all health authorities involved to stay on high alert.
Meanwhile, Hong Kong's acting chief executive Matthew Cheung Kin-chung said on Tuesday morning the government was prepared for the worst-case scenarios associated with the virus transmitting between humans.
Additional reporting by Alvin Lum
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