British travellers have been warned to be vigilant for symptoms of a killer pneumonia bug branded "a worldwide health threat" by the World Health Organisation (WHO).
Nine people have now died from the mystery strain, known as "severe acute respiratory syndrome", or SARS, which experts say cannot be stopped by standard drugs and has already reached three continents due to air travel.
Symptoms of the disease include fever, coughing, shortness of breath, headache, diarrhoea and muscle stiffness, but doctors understand little about severe acute respiratory syndrome.
It was not clear whether cases - including five deaths in China, one in Vietnam, one in Hong Kong and two in Canada - are linked or caused by one disease type or several strains. No one is sure whether bacteria or a virus is causing the illness.
A Department of Health spokeswoman said last night: "Travellers returning to the UK from any of these areas since 23rd February with sudden onset of high fever and one other symptom of pneumonia including cough, sore throat or shortness of breath, or muscle aches should seek medical advice."
With so few facts established, New Zealand prime minister Helen Clark said some officials inside WHO fear the possibility of an outbreak as "deadly as the 1918 influenza" pandemic that killed at least 20 million people.
But a WHO official in Vietnam, where a nurse became the latest fatality on Saturday, played down such worries. Pascal Brudon said : "Today we don't know enough about the outbreak to be able to say that."
He added that 10 other patients with the illness in Hanoi, where at least 31 have been infected, were "getting better and better".
However, authorities around Asia were taking precautions, with airports in China and Japan screening passengers for signs of the bug.
Some tourists in Hong Kong were seen wearing surgical masks as they left the airport, and travellers arriving at the international airport in Guangzhou, China, also wore masks or covered their faces with scarves.
Hong Kong travel agents specialising in package tours for south-east Asians have reported a 70 to 80% drop in bookings compared with the same period last year due to pneumonia fears, although there have not yet been any cancellations, an industry official said.
Joseph Tung, executive director of the Hong Kong Travel Industry Council, said: "This is a worldwide issue, and it will affect tourism globally, not just in Hong Kong."
