SARS is a relatively recently diagnosed disorder that usually begins with a fever often accompanied by other symptoms such as headache, malaise, myalgia, or diarrhea. Following this prodrome by approximately 3-7 days, the patient develops cough (not usually productive) and shortness of breath. Abnormalities in laboratory findings may include leukopenia, thrombocytopenia, and elevated levels of creatinine phosphokinase or transaminases. Chest x-ray findings vary from normal or near-normal to the classic alveolointerstitial pattern seen in ARDS. Both interstitial and alveolar infiltrates have been described. Because at present no specific test for SARS exists and the definition is quite broad, SARS is usually considered a diagnosis of exclusion. Cases have been found in over two dozen countries and the case-fatality rate has been under 10% as of this writing, well below the initially feared levels of lethality. Transmission is considered to be person-to-person and probably chiefly by droplet spread. The incubation period is 2-7 days. Most available evidence points to coronaviruses as the etiologic agents. The coronavirus heretofore had been considered mainly a causative agent of the common cold.