The illness, being called Severe Acute Respiratory Syndrome (SARS) and described as an "atypical pneumonia," appears to have killed at least nine people, including an American businessman in Hong Kong, a mother and son in Canada, and a nurse in Vietnam.
World Health Organization officials say there have been reports of more than 150 suspected new cases in just the last week. Most of those stricken, many of them hospital workers in southeast Asia, have severe breathing difficulties, according to news reports. The illness appears immune to antibiotics and antiviral drugs.
Canda has now reported 9 cases; Hanoi has reported at least 42 cases; Hong Kong has reported 49, including 42 medical workers; Tapei reported three people hospitalized with flu-like symptoms, and Singapore's toll has jumped to 20.
Singapore's Ministry of Health said Sunday that three Singapore residents who were in Hong Kong returned home ill and infected 10 family members and friends along with seven hospital workers who treated them, according to the The New York Times.
One of the newest cases, in Frankfurt, Germany, involves a Singapore doctor who was quarantined, along with his wife and mother-in-law, after flying out of New York City, where he had attended a medical conference. And on Sunday, news reports say a person who traveled from Georgia to Canda may also have been stricken.
The WHO advisory, sent Saturday to all airlines, warned that the illness was becoming "a worldwide health threat."
"Until we can get a grip on it, I don't see how it will slow down," WHO spokesman Dick Thompson said at the agency's headquarters in Geneva. "People are not responding to antibiotics or antivirals; it's a highly contagious disease, and it's moving around by jet. It's bad."
The CDC moved into emergency mode Saturday to alert health authorities at state and local levels.
"The emergence of two clusters of this illness on the North American continent indicates the potential for travelers who have been in the affected areas of Southeast Asia to have been exposed to this serious syndrome," CDC director Dr. Julie L. Gerberding said in a statement issued in Atlanta. "Therefore, we are instituting measures aimed at identifying potential cases among travelers returning to the United States and protecting the people with whom they may come into contact."
Among other things, the agency is now investigating any illness among travelers who may have passed through the United States after having potential exposure to the virus. It is also preparing health alert cards to give to travelers returning from southeast Asia.
And, while no formal travel restrictions are in place, travelers may wish to postpone nonessential trips to the countries at risk, Gerberding told a news conference.
In Frankfurt, hospital officials who were monitoring the Singapore surgeon said his condition had slightly worsened Sunday. His mother-in-law had a high fever, and his pregnant wife appeared to be OK, they added.
The 32-year-old doctor, who was not identified, was taken off a Singapore Airlines New York-to-Singapore flight during a stopover in Frankfurt, the Associated Press reports.The surgeon had treated one of the earliest cases in Singapore, and had then flown to a medical meeting in New York City, according to Thompson.
He may have gone to a hospital in New York -- the agency did not know which one -- before flying back. Before boarding the flight, he called a colleague in Singapore to describe his symptoms, and the colleague notified WHO officials, the Times reports.
The doctor, who was interviewed in Germany by New York health officials, said he had flown in to New York City on Wednesday and left on Friday. According to a New York City Health Department statement issued late Saturday, he also said he had had minimal contact with people in the city and had attended the medical conference for only a few hours.
The remaining passengers on the flight, along with the crew, were quarantined briefly at the airport. Ongoing Singapore passengers were put on another plane AP reports.
In Canada, meanwhile, Toronto health officials on Saturday confirmed a seventh local case connected to the deaths of two members of one family. Authorities had announced Friday that Kwan Sui-chu died on March 5 soon after returning from Hong Kong. Her son, Chi Kwai Tse, died on Thursday, and four other family members are hospitalized, the agency said.
The newest case, according to the Canadian Press, involves a person who had come in contact with the family, but no more details were available.
A spokeswoman for Toronto Public Health said the agency was aware of two other cases in Canada, both in Vancouver and both recent travelers to Hong Kong.
At least two other fatalities appear to be linked: The American businessman, who was based in Shangai, and the nurse, who died on Sunday in Hanoi. The man, who has not yet been identified, died of the illness March 6. But he apparently infected at least 37 hospital workers in Hanoi, where he was treated before being moved to Hong Kong, according to AP.
Additional cases include a man from the Philippines who visited Vietnam earlier this month and was then diagnosed with atypical pneumonia. And Guangdong province, which adjoins Hong Kong in China, had reported 305 cases with similar symptoms by mid-February, including five deaths.
A team of CDC epidemiologists arrived in Hanoi Saturday to gather samples and try to determine what's causing the outbreak. Scientists do not know whether SARS is a virus or even an infectious agent, health officials said. As a result, the research is focusing on the possibility that the illness is a previously unknown infectious agent, the AP reported.
WHO officials, who earlier this week issued their first global health alert in 10 years on the outbreaks, urged all countries to help.
The emergency travel advisory, while not calling for restrictions on travel, urged travelers who may have come in contact with an infected person to watch for such symptoms as high fever, coughing and shortness of breath. Health officials also urged people who suspect they may have the illness to seek medical attention and not travel until they recover.