Severe Acute Respiratory Syndrome (SARS): Coronavirus Infection

Description

Severe acute respiratory syndrome (SARS) is a novel respiratory illness that emerged in spring 2003. Outbreaks in south Asia followed reports of atypical pneumonia from Guangdong Province, China, the preceding November. A newly identified coronavirus, which may have spread to humans from a mammalian host, is believed to be the etiologic agent of SARS.

Occurrence

Cases of SARS have been reported in Asia, North America, and Europe. Although cases of SARS have been reported primarily among people who have had direct close contact with an infected person, such as those sharing a household with a SARS patient and health-care workers, SARS also has occurred among travelers, primarily travelers to and from Hong Kong, Hanoi, Singapore, and mainland China. At the height of the Spring 2003 outbreak, CDC issued travel advisories, recommending deferral of all but essential travel, for mainland China, Taiwan, Hong Kong, Singapore, and Hanoi, Vietnam; a travel alert, raising awareness of the presence of the disease, was issued for Toronto, Ontario, Canada. The advisories and alerts were removed when cases ceased to be reported.

Because SARS was unknown before 2003, no seasonal pattern of transmission can be described. However, viral respiratory infections, such as influenza, are known to recur seasonally. Continued vigilance for cases of SARS is warranted.

Risk for Travelers

Most of the U.S. cases of SARS have occurred among travelers returning to the United States from other parts of the world where SARS cases were occurring. Only one case was reported that might have occurred from spread within the United States. Cases elsewhere in the world resulted from local spread, most often from close contact in households and in health-care settings, where transmission occurred among family members, health-care workers, or visitors and patients in health-care facilities. At this time there is no evidence of SARS transmission anywhere in the world, but it is possible that SARS could return from its original source in animals or undetected infection or transmission in humans. The World Health Organization and CDC are looking for evidence of SARS transmission throughout the world and are maintaining up-to-date information on SARS worldwide. Travelers can get current information on SARS transmission at CDC’s Travelers’ Health website (http://www.cdc.gov/travel/). This website will have the latest travel alerts and advisories regarding SARS.

Clinical Presentation

The illness generally begins with a prodrome of fever (>100.4°F [>38.0°C]). Fever often is high, sometimes is associated with chills and rigors, and may be accompanied by other symptoms, including headache, malaise, and myalgia. The incubation period for SARS is typically 2–7 days; however, some reports have suggested an incubation period as long as 10 days. At the onset of illness, patients may 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 may be accompanied by or progress to hypoxemia. In 10%–20% of cases, the respiratory illness is severe enough to require mechanical ventilation. The case-fatality rate has been estimated to be 13.2% for patients <60 years of age and 43.3% for patients 60 years of age or more.

Chest radiographs may 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 also have shown areas of consolidation.

Prevention

To protect against SARS infection, CDC recommends frequent handwashing. Travelers to areas reporting SARS cases should avoid settings where SARS is most likely to be transmitted, such as health-care facilities caring for SARS patients. CDC does not recommend the routine use of masks or other personal protective equipment while in public areas.

Treatment

Because the clinical presentation is compatible with other causes of atypical pneumonia, empiric treatment regimens have included several antibiotics to presumptively treat known bacterial agents of atypical pneumonia. No specific treatment is available for the SARS coronavirus. Regimens used during the Spring 2003 outbreak failed to demonstrate efficacy.

For more information about SARS, see the CDC SARS site at http://www.cdc.gov/ncidod/sars.

— Ava Navin, Larry Anderson, and Phyllis Kozarsky