SARS case confirmed by China, WHO

And yesterday the World Health Organisation also confirmed the diagnosis. The agency had been conducting its own tests on samples from the patient to compare the level of SARS neutralising antibodies in the patient's blood over recent days with levels found early in the course of his disease. The results showed that the level of these antibodies had risen significantly, fitting the laboratory definition of SARS.

The announcements follow more than a week of speculation about the nature of his illness, with tests providing both positive and negative results. Worryingly, it has been suggested that the causative agent is the SARS coronavirus, but a variant not encountered before.

WHO said it is important to stress that although this case has now been classified as a SARS case, this does not indicate there is an immediate public-health threat in southern China, adding that it is safe to travel to all areas of China.

However, fear of a fresh SARS outbreak has already led to a crackdown on suspected cases at international airports.

The authorities in Malaysia have quarantined a women with fever who had returned from a tour of southern China, including Guangdong province where the suspected SARS case was discovered, although she is not thought to have the disease. Malaysia began screening airline passengers from Guangdong last month following news of the possible SARS case.

News of the outbreak will lend added urgency to ongoing efforts to develop vaccines and drugs to prevent and treat the disease. Earlier this year scientists identified one particularly promising new drug target, a viral protein called coronavirus main protease.

A drug developed by Pfizer subsidiary Agouron Pharmaceuticals for rhinovirus infections which are often behind the common cold is already in clinical trials and has shown some activity against the coronavirus protease. It could form a useful starting point for drugs specifically designed to treat SARS.