Severe acute respiratory syndrome (SARS) is a serious, potentially life-threatening viral infection caused by a previously unrecognized virus from the Coronaviridae family, the SARS-associated coronavirus (SARS-CoV). Since the 2002-2003 outbreak of SARS, which initially began in the Guangdong province of southern China but eventually involved more than 8000 persons worldwide (see the image below), global efforts have virtually eradicated SARS as a threat. No further cases have been reported.
World map of severe acute respiratory syndrome (SARS) distribution from the 2002-2003 outbreak infection. The greatest number of past and new cases of SARS are in mainland China, Hong Kong, Taiwan, and Singapore (red). Canada, more specifically Toronto, Ontario (yellow), is the fifth-ranked area, although community transmission of SARS now appears to be contained, according to the US Centers for Disease Control and Prevention. Green represents the other countries reporting SARS cases.
Signs and symptoms
The clinical course of SARS generally follows a typical pattern. Stage 1 is a flulike prodrome that begins 2-7 days after incubation, lasts 3-7 days, and is characterized by the following:
Fever (>100.4°F [38°C])
Less common features include the following
Nausea and vomiting
Stage 2 is the lower respiratory tract phase and is characterized by the following:
Progressive hypoxemia in many cases
Respiratory failure that requires mechanical ventilation in some cases
See Clinical Presentation for more detail.
Initial tests in patients suspected of having SARS include the following:
Sputum Gram stain and culture
Viral respiratory pathogen tests, notably influenza A and B viruses and respiratory syncytial virus
Legionella and pneumococcal urinary antigen testing should also be considered
Data from the 2002-2003 outbreak indicate that SARS may be associated with the following laboratory findings
Modest lymphopenia, leukopenia, and thrombocytopenia: Series have shown white blood cell (WBC) counts of less than 3.5 x 109/L and lymphopenia of less than approximately 1 x 109/L
Mild hyponatremia and hypokalemia
Elevated levels of lactate dehydrogenase, alanine aminotransferase, and hepatic transaminase
Elevated creatine kinase level
According to guidelines from the Centers for Disease Control and Prevention (CDC), the laboratory diagnosis of SARS-CoV infection is established on the basis of detection of any of the following with a validated test, with confirmation in a reference laboratory
Serum antibodies to SARS-CoV in a single serum specimen
A 4-fold or greater increase in SARS-CoV antibody titer between acute- and convalescent-phase serum specimens tested in parallel
Negative SARS-CoV antibody test result on acute-phase serum and positive SARS-CoV antibody test result on convalescent-phase serum tested in parallel
Isolation in cell culture of SARS-CoV from a clinical specimen, with confirmation using a test validated by the CDC
Detection of SARS-CoV RNA via reverse transcriptase polymerase chain reaction (RT-PCR) assay validated by the CDC, with confirmation in a reference laboratory, from (1) two clinical specimens from different sources or (2) two clinical specimens collected from the same source on 2 different days
Chest radiography results in SARS are as follows:
In one study, abnormalities were found on initial studies in approximately 60% of patients and were observed in serial examinations in nearly all patients by 10-14 days after symptom onset
Interstitial infiltrates can be observed early in the disease course
As the disease progresses, widespread opacification affects large areas, generally starting in the lower lung fields
High-resolution computed tomography (HRCT) scanning is controversial in the evaluation of SARS but may be considered when SARS is a strong clinical possibility despite normal chest radiographs.
HRCT findings consistent with SARS include the following:
In early-stage SARS, an infiltrate in the retrocardiac region
Ground-glass opacification, with or without thickening of the intralobular or interlobular interstitium
See Workup for more detail.
No definitive medication protocol specific to SARS has been developed, although various treatment regimens have been tried without proven success.
The CDC recommends that patients suspected of or confirmed as having SARS receive the same treatment that would be administered if they had any serious, community-acquired pneumonia.
The following measures may be used:
Isolate confirmed or suspected patients and provide aggressive treatment in a hospital setting
Mechanical ventilation and critical care treatment may be necessary during the illness.
An infectious disease specialist, a pulmonary specialist, and/or a critical care specialist should direct the medical care team
Communication with local and state health agencies, the CDC, and World Health Organization is critical
See Treatment and Medication for more detail.