Reports of the cover-up emerged as it was announced that Carlo Urbani, 46, an expert from the World Health Organisation who raised the alarm over the disease while working in Vietnam, has died of it.

Suspected cases of the illness, known as severe acute respiratory syndrome (Sars), have now occurred in other countries including Vietnam, Singapore, America and Canada. The disease has also spread to other parts of China.

At least 55 people have died and 1,485 are ill — the largest number in Guangdong province in southern China, of which Guangzhou is the capital.

Authorities in Hong Kong are preparing to invoke a colonial-era quarantine law to isolate 1,000 suspected sufferers in their homes. They also intend to impose border health checks from tomorrow. In Singapore some 700 people have been put into quarantine.

Western health experts have criticised the secretiveness of Chinese officials, saying it has delayed efforts to combat the disease. The Chinese have only recently agreed to allow doctors to share a few details of case histories and treatment.

Western diplomats in Guangzhou were warned by friends at hospitals in January that a virulent form of pneumonia had killed dozens of people. However, officials continued to deny that anything was wrong.

Chinese journalists, who asked not to be identified, said the party’s propaganda department vetoed any mention of the outbreak. “It was stupid,” said one reporter in the city. “The result was that rumours and panic spread.” Within days shops sold out of disinfectant and cold medicines as people tried to protect their families. Panic buying of foodstuffs also occurred as some feared the authorities might impose a curfew.

Chinese journalists believe that officials feared that news of the disease would spoil the city’s image, since it was known that the spread of the virus was linked to a form of unhygienic behaviour — spitting. This is a common habit in southern China, where most people cough and sneeze without covering their faces. Pools of saliva are frequent sights in restaurants, trains and buses.

Epidemiologists say such practices, combined with overcrowding and pollution, plus a history of viral outbreaks jumping from pigs and poultry to humans, make Guangdong province one of the world’s most dangerous breeding grounds for infectious viruses.

The virus appears to have become an international problem after Liu Jianlun, 64, a doctor in Guangzhou, travelled to Hong Kong and infected other guests in a hotel. He became ill but before he died he told doctors that he knew he was suffering from a highly contagious type of pneumonia.

The Chinese cover-up continues. Reporters in Hong Kong say victims in Guangzhou are still too frightened to talk.

In Shanghai, where rumours of an outbreak spread last week, officials have banned Chinese journalists from reporting anything but official statements. The foreign press has been told to be “responsible” because reporting the outbreak would be “bad for the business environment”.

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