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 provides a summary of the clinical characteristics of SARS patients treated in Hong Kong Special Administrative Region (China), Taiwan (China), Thailand, 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 non-specific case definition.
Most patients identified as of March 21, 2003 have been previously healthy adults aged 25-70 years. A few suspected cases of SARS have been reported among children (≤15 years).
The incubation period of SARS is usually 2-7 days but may be 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 diarrhoea during the febrile prodrome.
After 3-7 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%-20% of cases, the respiratory illness is severe enough to require intubation and mechanical ventilation. The case fatality among persons with illness meeting the current WHO case definition for probable and suspected cases 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 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 cell counts have generally been normal or decreased. At the peak of the respiratory illness, up to 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 3000 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.
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 regime, if any is unknown.