The Centers for Disease Control and Prevention (CDC) and the World Health Organization (WHO) are investigating a worldwide outbreak of unexplained atypical pneumonia referred to as Severe Acute Respiratory Syndrome (SARS).
As of 10 April 2003, over 2,500 suspected cases of SARS have been reported to WHO from nearly 20 countries; in the United States, over 150 suspected cases (about 5% of cases worldwide) have been reported to CDC from about 30 states. Of the United States cases, about 95% had traveled to outbreak areas listed in the case definition within 10 days prior to the onset of clinical illness, and the remainder had a history of close contact with a person with suspected SARS.
Of these cases reported worldwide, approximately 3.5 % (over 100 cases) have been fatal. In the United States, the majority of patients have recovered or stabilized clinically without specific antiviral therapy; no fatalities have been reported as of 10 April 2003.
Laboratories at CDC and elsewhere (SARS Laboratory Network organized by WHO) have detected a new coronavirus in SARS patients. Less often, a paramyxovirus (metapneumovirus) also has been found. Both are lipid-enveloped, singlestranded RNA viruses. The identification of a novel coronavirus is consistent with a potential etiologic role, but the pathogenesis of SARS remains unclear at the present early stage of research. A co- factor role of paramyxovirus in this syndrome cannot be excluded. A diagnostic test for SARS based on the detection of acute infection with the novel coronavirus is currently under development.