During the past week, WHO has received reports of more than 150 new suspected cases of Severe Acute Respiratory Syndrome (SARS), which the agency called "an atypical pneumonia for which cause has not yet been determined."

Canada, China, Hong Kong Special Administrative Region of China, Indonesia, the Philippines, Singapore, Thailand and Viet Nam have all reported cases of the illness. Early today, a sick passenger and companions who travelled from New York to Frankfurt were removed from their flight and taken to hospital isolation.

"This syndrome, SARS, is now a worldwide health threat," said WHO chief Dr. Gro Harlem Brundtland. "The world needs to work together to find its cause, cure the sick, and stop its spread."

While the agency is not recommending that people restrict travel to any destination, it is advising travellers and airline crew to take certain precautions aimed at identifying and helping those affected by SARS, which is characterized by high fever and respiratory symptoms such as cough, shortness of breath or difficulty breathing.

WHO is urging airlines to transfer any infected persons to a hospital for isolation, assessment and care. But the agency is not calling for any restrictions on the onward travel of healthy passengers who shared a flight with the sick individual.