Volume 29-08
15 April 2003

[Table of Contents]

PRELIMINARY CLINICAL DESCRIPTION OF SEVERE ACUTE RESPIRATORY SYNDROME

Severe acute respiratory syndrome (SARS) is a disease of unknown etiology that has been described in patients in Asia, North America, and Europe. The information in this report represents a summary of information collected by the World Health Organization (WHO), Health Canada, and the Centers for Disease Control and Prevention (CDC) in collaboration with health authorities and clinicians in Hong Kong, Taiwan, Bangkok, Singapore, the United Kingdom, Slovenia, Canada, and the United States since mid-February 2003. This information is preliminary and subject to limitations because of the broad and necessarily non-specific case definition.

Most patients identified as of 21 March, 2003, were previously healthy adults aged 25 to 70 years. Few suspected cases of SARS have been reported among children (<= 15 years).

The incubation period of SARS is usually 2 to 7 days, but isolated reports have suggested an incubation period as long as 10 days. The illness generally begins with a prodrome of fever (> 38° C), which is often high, sometimes associated with chills and rigors and sometimes accompanied by other symptoms, including headache, malaise, and myalgias. At the onset of illness, some cases have mild respiratory symptoms. Typically, rash and neurologic or gastrointestinal findings are absent, although a few patients have reported diarrhea during the febrile prodrome.

After 3 to 7 days, a lower respiratory phase begins with the onset of a dry, non-productive cough or dyspnea that may be accompanied by or progress to hypoxemia. In 10% to 20% of cases, the respiratory illness is severe enough to require intubation and mechanical ventilation. The case fatality rate among people with illness meeting the current WHO case definition of SARS is around 3%.

Chest radiographs may be normal during the febrile prodrome and throughout the course of illness. However, in a substantial proportion of patients, the respiratory phase is characterized by early focal interstitial infiltrates progressing to more generalized, patchy, interstitial infiltrates. Some chest radiographs from patients in the late stages of SARS have also shown areas of consolidation.

Early in the course of disease, the absolute lymphocyte count is often decreased. Overall, white blood cell counts have generally been normal or decreased. At the peak of the respiratory illness, up to one-half of patients have leukopenia and thrombocytopenia or low-normal platelet counts (50,000-150,000/µL). Early in the respiratory phase, elevated creatine phosphokinase levels (up to 3,000 IU/L) and hepatic transaminases (2 to 6 times the upper limits of normal) have been noted. Renal function has remained normal in the majority of patients.

The severity of illness may be highly variable, ranging from a mild illness to death. Although a few close contacts of patients with SARS have developed a similar illness, most have remained well. Some close contacts have reported a mild, febrile illness without respiratory signs or symptoms, suggesting that the illness may not always progress to the respiratory phase.

Treatment regimens have included a variety of antibiotics to presumptively treat known bacterial agents of atypical pneumonia. In several locations, therapy has also included antiviral agents such as oseltamivir or ribavirin. Steroids have also been given orally or intravenously to patients in combination with ribavirin and other antimicrobials. At present, the most efficacious treatment regimen, if any, is unknown.

Clinicians who suspect cases of SARS are requested to report such cases to their local public health authorities. Additional information about SARS, including updates on the Canadian situation, a travel advisory and fact sheets, is available at the Health Canada Web site. Global case counts are available at http://www.who.int.

Acknowledgements

This report is based on data provided by A McGeer, MD, and S Poutanen, MD, Mount Sinai Hospital, University of Toronto, Toronto; DE Low, MD, Mount Sinai Hospital and University Health Network, University of Toronto, Toronto; S Finkelstein, MD, Scarborough Grace Hospital, Toronto; I Salit, MD, University Health Network, University of Toronto, Toronto; B Henry, MD, Toronto Public Health, Toronto; A Simor, MD, Sunnybrook and Women's College Hospital, University of Toronto, Toronto; W Bowie, MD, E Bryce, MD, K Craig, MD, P Doyle, MD, J Ronco, MD, and F Ryan, MD, University of British Columbia and Vancouver Hospital and Health Sciences Center, Vancouver; L Srour, MD, BC Centre for Disease Control, Vancouver; SC Chang, MD, YC Chen, MD, PR Shueh, MD, GY Chen, MD, and BH Kuo, MD, National Taiwan University Hospital, Taipei, Taiwan; Shew-Dan Chen, MD, Ilan Hospital, Ilan, Taiwan; Ming-Shian Liin, MD, Chia-Yi Christian Hospital, Chia-Yi, Taiwan; Tzay-Jinn Chen, MD, Long-Teng Lee, MD, Shiing-Jer Twu, MD, Taiwan Center for Disease Control, Taipei; S Tansuphaswadikul, MD, V Pinyowiwat, MD, and J Wongsawat, MD, Bamrasnaradura Institute, Nonthaburi, Thailand.

Source: WHO, Geneva, Switzerland; Immunization and Respiratory Infections Division, Centre for Infectious Disease Prevention and Control, Health Canada, Ottawa, Canada; CDC SARS Investigation Team. 

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