Severe acute respiratory syndrome (SARS) is a condition of unknown etiology that has been described in patients in Asia, North America, and Europe. This report summarizes the clinical description of patients with SARS based on information collected since mid-February 2003 by the World Health Organization (WHO), Health Canada, and CDC in collaboration with health authorities and clinicians in Hong Kong, Taiwan, Bangkok, Singapore, the United Kingdom, Slovenia, Canada, and the United States. This information is preliminary and limited by the broad and necessarily nonspecific case definition. As of 21 Mar 2003, the majority of patients identified as having SARS have been adults aged 25--70 years who were previously healthy. Few suspected cases of SARS have been reported among children aged <15 years.
The incubation period for SARS is typically 2--7 days; however, isolated reports have suggested an incubation period as long as 10 days. The illness begins generally with a prodrome of fever (greater than 100.4 F [greater than 38.0 C]). Fever often is high, sometimes is associated with chills and rigors, and might be accompanied by other symptoms, including headache, malaise, and myalgia.
At the onset of illness, some persons have mild respiratory symptoms. Typically, rash and neurologic or gastrointestinal findings are absent; however, some patients have reported diarrhea during the febrile prodrome. After 3--7 days, a lower respiratory phase begins with the onset of a dry, nonproductive cough or dyspnea, which might be accompanied by or progress to hypoxemia. In 10--20 percent of cases, the respiratory illness is severe enough to require intubation and mechanical ventilation.
The case-fatality rate among persons with illness meeting the current WHO case definition of SARS is approximately 3 percent [based on today's data with the additional information from China, 49 deaths reported and 1323 cases the observed case fatality rate is now 3.7 percent - Mod.MPP]. Chest radiographs might 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 also have 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, approximately 50 percent of patients have leukopenia and thrombocytopenia or low-normal platelet counts (50 000 - 150 000 / microL).
Early in the respiratory phase, elevated creatine phosphokinase levels (as high as 3000 IU/L) and hepatic transaminases (2 to 6 times the upper limits of normal) have been noted. In the majority of patients, renal function has remained normal. The severity of illness might be highly variable, ranging from mild illness to death. Although a few close contacts of patients with SARS have developed a similar illness, the majority have remained well.
Some close contacts have reported a mild, febrile illness without respiratory signs or symptoms, suggesting the illness might not always progress to the respiratory phase. Treatment regimens have included several antibiotics to presumptively treat known bacterial agents of atypical pneumonia. In several locations, therapy also has included antiviral agents such as oseltamivir or ribavirin. Steroids have also been administered orally or intravenously to patients in combination with ribavirin and other antimicrobials. At present, the most efficacious treatment regimen, if any, is unknown.
We are posting this for the benefit of clinician subscribers who might not have seen cases of SARS and would be interested in the current clinical description and discussions. As more information on the clinical presentation and treatment guidelines become available we shall post these as well.
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