The first detailed study of the spread of the SARS virus in Hong Kong has found that the death rate among sufferers was much higher than previously estimated.
According to the World Health Organization (WHO), the death rate from the virus was 5 per cent. But the new study - the first to be based on a statistically sound sample of 1,425 cases - puts the death rate at one in five or 20 per cent.
However, experts warn that the figures do not reflect the chances of an average person anywhere dying from a bout of SARS once it is contracted.
The study focused on hospital patients in Hong Kong that had an average age of 50. The Lancetstudy, by scientists at Imperial College in London, the University of Hong Kong and the Hong Kong health authorities, estimated that the death rate could be as high as 55 per cent in people over the age of 60.
In people under 60, the death rate could be as low as 6.8 per cent, the study found. "That's sadly still very high for a respiratory infection," said Dr Roy Anderson, a professor of infectious disease epidemiology at Imperial College.
"In other common respiratory infections it is much less than 1% in the vulnerable elderly."
And scientists fear that the fact that the death rate from SARS appears to be higher than first thought may be a sign that the virus is mutating into more deadly forms.
Researchers found that, on average, it takes just over six days for clinical symptoms to show after a person is infected.