Results of first major study of SARS show early hospital admission key to tackling epidemic

Research by UK epidemiologists and scientists from Hong Kong reports results of the first major epidemiological study about severe acute respiratory syndrome (SARS). Authors of the study highlight how concerted efforts to reduce the time from the onset of symptoms to quarantining in hospital is one of the most important public-health measures to reduce transmission and to potentially eradicate the disease.

Christl Donnelly, Roy Anderson, and colleagues from Imperial College London, UK, the University of Hong Kong, and the Department of Health in Hong Kong, studied 1425 SARS cases from Hong Kong up to April 28, 2003. They report how, after the initial phase of exponential growth in SARS cases, public-health interventions have led to confirmed SARS cases dropping below 20 per day by April 28. Examples of such measures include the encouragement to report to hospital rapidly after the onset of clinical symptoms, the tracing of contacts of confirmed and suspected cases and quarantining, and the monitoring and restriction of travel for contacts.

The average incubation period of SARS (the time between infection and the onset of symptoms) was estimated to be 6.4 days; the average time from the onset of clinical symptoms to hospital admission varied from three to five days-with longer intervals reported earlier in the epidemic. The case fatality rate, among those admitted to hospital, in patients 60 years of age and older is estimated to be far higher (43.3%, 95% confidence interval 35.2 to 52.4%) than in those below 60 (13.2%, 95% confidence interval 9.8 to 16.8%). Similar estimates were obtained using a second method: 55.0% (95% confidence interval 45.3 to 64.7%) for those aged 60 or older and 6.8% (95% confidence interval (95% confidence interval 4.0 to 9.6%) in those younger than 60. Furthermore, they comment that additional infections in the community that do not lead to hospitalisation or death would lower this fatality-rate estimate.

Christl Donnelly comments: "Although this study shows that the fatality rate from SARS is higher than previously thought, we now know that public-health interventions have been successfully reducing the spread of the disease."

Roy Anderson comments: "The epidemic has demonstrated the need for communication of risk which will inform and warn the public, in a way which will improve personal protection, without inducing high levels of anxiety and fear, as an essential part of epidemic control. A change in risk perception would potentially lead to an increase in early reporting of symptoms as well as improvements in hygiene and prevention of transmission."

Contact: Tony Stephenson, Press Office, Imperial College, London SW7 2AZ, UK;
T) 44-207-594-6712;
F) 44-207-594-6700;
E) at.Stephenson@imperial.ac.uk

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