China's Ministry of Health is urging medical authorities across the nation to be on the lookout for signs of a deadly SARS-like virus which has been detected in Britain and Saudi Arabia.
No cases have been reported on the Chinese mainland so far, China National Radio reported yesterday.
However, in Hong Kong, there were fears that a four-year-old Saudi Arabian boy had been infected with the virus, known as a novel coronavirus.
The boy arrived in Hong Kong from Saudi Arabia last Wednesday with his father.
On Sunday, he showed symptoms of severe respiratory illness, including fever, cough and vomiting, and was transferred to Queen Mary Hospital.
Yesterday, the city's Center for Health Protection said tests showed he had H1N1 flu. He tested negative for the novel coronavirus.
The boy has upper respiratory tract symptoms but there was no evidence of pneumonia and he was currently in a stable condition, a center spokesman said.
The new virus comes from the same family as SARS which emerged in China in late 2002 and killed around a tenth of the 8,000 people it infected worldwide.
Late last month, the World Health Organization said that the novel coronavirus had left a Qatari citizen in a critical condition in a London hospital and had caused the death of a man in Saudi Arabia.
The Hong Kong center is suggesting that anyone coming from countries affected by the novel coronavirus and who show respiratory symptoms should wear a mask, seek medical attention and reveal their travel history to a doctor.
China's health ministry has ordered authorities to strengthen medical inspections on travelers from Britain, Saudi Arabia and Qatar and to report suspected cases to the ministry immediately.
China's quarantine authority is also requiring travelers from affected countries to inform China's entry-exit inspection and quarantine institutions if they develop acute respiratory symptoms such as fever, cough or shortness of breath.
It remains unknown whether this potentially fatal virus will cause another outbreak or if it will disappear into nothing, said Wang Shiwen, an official with the China Center of Disease Control and Prevention.
In a statement, the WHO said: "From the information available thus far, it appears that the novel coronavirus cannot be easily transmitted from person to person."
Coronaviruses are typically spread in the air but scientists were considering the possibility that patients could be infected directly by animals, said Gregory Hartl, a WHO spokesman.
No new confirmed cases of infection have been reported, the WHO said.
In Shanghai, health authorities said no special measures were being taken at present.