Labs around the world are now working frantically to identify the agent that is causing the syndrome, which has killed about 10 people and sickened hundreds more.

It took several months for Chinese authorities to report what may have been the beginning of the outbreak last November, the experts said. They added that hospitals in many affected countries have not taken the kinds of samples from patients that are needed to identify the infectious agent.

"Severe acute respiratory syndrome (SARS) is such a dramatic example of the importance of global surveillance and response capacity," Dr. James Hughes, head of the US Centers for Disease Control and Prevention's National Center for Infectious Diseases, told reporters in a telephone interview.

"When you first see a cluster, people need to recognize that these clusters have global implications."

The World Health Organization reported 219 official cases and four deaths from the disease. Chinese authorities said they believed five others died there.

Most cases have been in populous Hong Kong, where 123 people are ill and two are reported to have died. Vietnam has reported 57 cases and one death, while Singapore has 23 sick people. Two patients also died in Canada.

Doctors in Germany said they were treating three people with the illness, including a 32-year-old doctor from Singapore and his pregnant wife. The physician had treated some of the first pneumonia cases in the island republic.

WHO experts are expected to arrive in China to determine if the pneumonia is linked with an outbreak of respiratory disease that began in southern China in November and has struck than 300 people.

Suspected cases have been reported in Australia, Britain, Spain and the United States. On Tuesday the CDC revised the number of possible cases to nine from 14.

Numbers Constantly Changing

"We are constantly adding and dropping potential cases," Hughes said.

Infectious disease experts have for years spoken of how any disease is now only an airline flight away from anywhere, and the SARS outbreak has indeed spread via air travel from Asia to Europe, North America and Australia.

It has also followed the predicted patterns of either a new natural outbreak or a biological attack in that the symptoms look like a plethora of diseases -- fever, dry cough, aches.

Scientists have looked for evidence of dozens of different bacteria and viruses that could cause the illness, but found no strong clues yet. Many suspect it is something they have not seen before.

"As time goes by, that is increasingly likely, simply because so many people have run so many tests," said WHO spokesman Iain Simpson. "If it is something we already knew about we would almost certainly have identified it."

The CDC's Hughes said one frustration has been a lack of good samples to test. "First we need an accurate description of the clinical syndrome," he said. Doctors have reported antibiotics or antivirals have not affected the disease so far, but Hughes said more specimens are needed.

"We would like to get diagnostic specimens handled in an appropriate way," he added -- noting that it is easier to find germs in patients' blood soon after they are infected.

The illness begins with a high fever and dry cough that can lead to breathing difficulties and force the use of a respirator. Most cases have been in health workers or people with close contact to those who are ill.

Despite the growing number of suspected and confirmed cases, precautions taken when treating people suspected of having the illness have limited the number of new cases.

"We are not suddenly seeing hundreds or thousands of new cases in new countries. It suggests that it does not spread particularly easily or particularly quickly, which for us is good news," said Simpson. (Additional reporting by Patricia Reaney in London, Tan Ee Lyn, Alice Hung in Taipei, Jacqueline Wong in Singapore, Christina Pantin in Hanoi, Rosemarie Francisco in Manila, Jonathan Ansfield in Beijing; Richard Waddington in Geneva)

(China Daily March 19, 2003)