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Severe acute
respiratory syndrome (SARS) is caused by a coronavirus, is probably
spread by respiratory droplets, and has an incubation of 2 to 10
days. It produces an influenza-like illness that occasionally leads
to progressively severe respiratory insufficiency. The mortality
rate is 10%. Diagnosis is clinical. To prevent spread, patients
are isolated. Treatment is supportive.
Coronaviruses are enveloped RNA viruses. Coronaviruses 229E and OC43 have long been known to produce the common cold. In late 2002, an outbreak of a viral respiratory illness labeled SARS occurred. SARS is caused by a coronavirus (SARS-CoV) that is genetically dissimilar from known human or animal coronaviruses.
SARS-CoV appears to be a new human pathogen that was first detected in the Guangdong province of China in November 2002. Evidence of SARS-CoV infection has also been found in masked palm civets, raccoon dogs, and the Chinese ferret badger. SARS has spread to > 30 countries. As of mid-July 2003, over 8000 cases had been reported worldwide, with over 800 deaths (about 10% case mortality rate); since late 2003, naturally occurring cases appear to be contained to China.
Transmission of SARS-CoV is probably mainly by respiratory droplets and generally requires close personal contact. However, transmission can occur after very casual contact and possibly by aerosol spread. Infection primarily involves people between the ages of 15 and 70 yr.
Symptoms,
Signs, and Diagnosis
The incubation period is 2 to 10 days (median 5 days). Initial symptoms resemble influenza, with fever, cough, chills, rigor, and myalgia. Upper respiratory symptoms (runny nose, sore throat) are uncommon. Most patients have a mild illness and recover within 1 to 2 wk. Other patients develop respiratory distress, usually > 1 wk after symptom onset, with marked dyspnea, hypoxemia, and occasionally acute respiratory distress syndrome (ARDS). Death is due to respiratory failure.
Because initial symptoms are nonspecific, SARS is suspected in patients with likely exposure (based on epidemiologic factors) as well as fever and suggestive clinical symptoms. Suspected cases are reported to the state health department and evaluated by standard procedures for severe community-acquired pneumonia. Chest x-ray is frequently normal early in the illness. As respiratory symptoms worsen, focal interstitial infiltrates are common, which occasionally become generalized and sometimes progress to ARDS.
Typical laboratory tests are nonspecific, but WBC counts are usually normal or decreased, sometimes with a decrease in absolute lymphocyte count. Transaminases, CPK, or LDH may be elevated, but renal function remains normal. If chest CT is obtained, it may show peripheral, subpleural ground-glass opacifications.
Viral cultures for known respiratory pathogens (eg, influenza, respiratory syncytial virus) are obtained using swabs from the oropharynx and nasopharynx, and the laboratory is notified that SARS is suspected. Although serologic and PCR tests have been developed for detection of SARS-CoV, they are not useful for clinical management. For epidemiologic surveillance, acute and convalescent (3-wk) serum specimens are sent to state or local health departments to be forwarded to the Centers for Disease Control and Prevention for testing.
Prognosis,
Treatment,
and Prevention
Predictors of death appear to be age > 60 yr, comorbidity, increased LDH levels, and increased absolute neutrophil count. Treatment of SARS is supportive, with mechanical ventilation as needed. Oseltamivir , ribavirin , and corticosteroids have been used, but there is no current evidence of benefit.
Patients suspected of having SARS should be placed in isolation in a negative-pressure room. Contact and respiratory precautions should be taken. Staff should use N-95 masks, eye protection, gloves, and gowns.
People exposed to patients suspected of having SARS (eg, family members, airline personnel, health care practitioners) should be alert for symptoms of illness. In the absence of symptoms, such people may attend work, school, and other activities as usual. If fever or respiratory symptoms develop, they should limit their public activities and seek medical evaluation. If symptoms do not progress to meet suspect SARS criteria within 72 h, they may return to normal activity as tolerated.
Last full review/revision November 2005
Content last modified November 2005
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