Severe acute respiratory syndrome (SARS) has recently been recognized as a newly emerging infectious disease that is highly contagious with significant morbidity and mortality. Earliest cases of SARS has been described in patients in Asia, North America, and Europe. Etiological agent of SARS is shown to be a coronavirus. Most coronaviruses cause disease in only one host species. All known coronaviruses are found in three serologically unrelated groups. A corona of large, distinctive spikes in the envelope makes possible the identification of coronaviruses by electron microscopy. In this way the first identification of agent was possible. Microbiologic and genetic analyses have shown that the SARS-associated coronavirus is neither a mutant nor a recombinant of any known coronaviruses. It is a previously unknown coronavirus, probably from a nonhuman host, that somehow acquired the ability to infect humans. Serologic tests of wild and domestic animals and birds in the region where the outbreak first appeared may identify the usual host. 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 (>38.0°C). Fever often is high, is sometimes 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% 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%. 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 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, approximately 50% 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 (as high as 3,000 IU/L) and hepatic transaminases (2-6 times the upper limits of normal) have been noted. Treatment regimens have included several 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 administered orally or intravenously to patients in combination with ribavirin and other antimicrobials. Although there are no approved drugs with proven efficacy against coronaviruses, there are potential targets for the development of new drugs. Protease inhibitors could prevent processing of the RNA polymerase or cleavage of the viral S glycoprotein. Inhibitors of coronavirus acetylesterase activity might limit viral replication.

Anahtar Kelimeler: severe acute respiratory syndrome (SARS), emerging infection, pneumonia, atypic pneumonia