Scientists continue to gain new insights into how the deadly disease - SARS spread so quickly during last year's outbreak.
The latest discovery researchers have made is that the virus doesn't always cause the pneumonia doctors believe is typical of the disease. They say that explains why some people got SARS even though it looked as if they'd never been around anyone who had the disease.
Investigators at the University of Hong Kong conducted laboratory studies on blood taken from healthy people who donated blood during the outbreak, patients who were in the hospital at the time but didn't have pneumonia, and health care workers who were also on duty during the epidemic but never developed any symptoms of the disease.
Three of the healthy people and one of the patients without pneumonia were found to have antibodies to the virus, leading the researchers to conclude SARS may cause asymptomatic or mild infections that go undetected -- but are still capable of spreading the disease.