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Five patients triggered outbreak Original Source Link: (May no longer be active)
http://quote.bloomberg.com/apps/news?pid=10000080&sid=aZY4qNuUCgVU&refer=asiahttp://quote.bloomberg.com/apps/news?pid=10000080&sid=aZY4qNuUCgVU&refer=asia
Five Patients Spread SARS to Scores, Study Says (Update2)
By John Lauerman
Atlanta, May 8 (Bloomberg) -- Five particularly infectious patients may have triggered the Singapore outbreak of severe acute respiratory disease that health officials have just brought under control, according to a study published by the U.S. Centers for Disease Control and Prevention.
Researchers investigating how at least 7,053 people around the world have caught the respiratory disease in six months have traced the path of SARS from Hong Kong through Singapore's hospitals and streets. The illness has killed at least 506 people worldwide, 27 of them in Singapore.
Disease trackers say the five ``super-spreaders'' probably transmitted the contagion to at least 144 of the 204 people infected in Singapore, and one person may have passed the coronavirus that causes the disease to at least 40 people. While the U.S. checks incoming travelers for symptoms, there is no way to know who the super-spreaders are, said Julie Gerberding, head of the U.S. Centers for Disease Control and Prevention.
``We can't tell up front who's going to be infectious and who isn't,'' she said in a telephone call with reporters. ``This is part of the reason that we continue to send the message in this country that we have to remain vigilant.''
Singapore has stiffened legal penalties for people who break quarantine and has urged everyone to seek medical attention for fevers or other SARS symptoms, study leader Yee Sin Leo of the Tan Tock Seng Hospital in Singapore wrote in research that will appear in the CDC's Morbidity and Mortality Weekly Report tomorrow.
Ripples of Infection
All five people characterized as super-spreaders were linked to a 22-year-old guest at Hong Kong's Metropole Hotel. The contagion spread to hundreds of health-care workers in Hong Kong and air travelers carried the disease to the U.S., Canada, Ireland, and Vietnam, according to an earlier CDC study.
The seed of one outbreak was planted when the Metropole guest developed the dry SARS cough in late February and was admitted to Tan Tock Seng Hospital in Singapore. Nine health-care workers and 12 family members caught the disease and developed pneumonia, in the first ring of contagion.
The second level of infection began with a 27-year-old nurse who cared for the hotel guest at Tan Tock Seng. The nurse fell ill on March 7 and infected 11 health-care workers and 12 family members.
After the nurse was hospitalized, she transmitted the disease to a patient sharing her room, which led to a third group of 23 infections.
Common Denominator
The final ripple began when the nurse passed the respiratory infection to a 60-year-old patient also being treated at Tan Tock Seng for diabetes and kidney disease. That patient was discharged and later admitted to Singapore General Hospital. From there, 25 staff members, 20 patients, and 17 family members were infected with severe acute respiratory syndrome.
Of the total number of patients infected, 40 developed pneumonia and one of them, a vegetable merchant, died after passing the disease to 15 more people.
Researchers still aren't sure what super-spreaders have in common, Gerberding said. They may happen to have contact with many people who are not actively trying to prevent infection, or may simply cough more than others, she said.
``We do think there's a biological reason'' such as more virus shedding, Annelies Wilder-Smith, head of a travel medicine center at Tan Tock Seng Hospital, said in an interview. ``It is a very important question because if we can identify the super- spreaders earlier then we can stop, or can control, the epidemic.''
Long Suspected
The CDC lifted its advisory against nonessential travel to Singapore Tuesday, citing the lack of new SARS cases, outside of health-care workers or close family members of infected patients. The advisory ended one day before the two nations signed a free- trade agreement allowing U.S. companies to expand their base in Singapore, the largest U.S. trading partner in Southeast Asia.
Scientists have suspected super-spreaders played a role in the epidemic since its beginning. CDC disease trackers said that in February, a doctor from the Chinese province of Guangdong spread the disease to 10 guests at the Metropole Hotel, two hospital workers, and two family members.
Another guest at the hotel has been linked to at least 37 cases of the disease in Hanoi, Vietnam. That patient was an American businessman who could just as easily have caused an outbreak in this country, Gerberding said.
``We, too, could have a cascade of transmission established, we certainly are not immune to that,'' she said.
Last Updated: May 8, 2003 16:40 EDT
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