Severe Acute Respiratory Syndrome

Description

Severe acute respiratory syndrome (SARS) is a febrile respiratory illness caused by a novel coronavirus, SARS-associated coronavirus (SARS-CoV), which emerged in southern China in November 2002. SARS-CoV is believed to be of zoonotic origin; although several animal species (e.g., civet cats, raccoon dogs) sold for human consumption in markets in southern China have demonstrated evidence of SARS-CoV infection, the natural reservoir of SARS-CoV is unknown.

Occurrence

During November 2002-July 2003, more than 8,000 probable SARS cases, 774 of them fatal, were reported from 29 countries, with most cases in China, Hong Kong, Taiwan, Singapore, and Canada. In the United States, only 8 patients were confirmed to have laboratory evidence of SARS-CoV infection.

From July 2003 through September 2004, 17 laboratory-confirmed SARS cases were reported. Six persons were infected through laboratory exposures: one in Singapore, one in Taiwan, and four in China. One of these six cases initiated a chain of transmission that ultimately resulted in seven additional cases and one death. All the laboratory-acquired infections resulted from lapses in appropriate biosafety procedures.

In addition, in December 2003 and January 2004, four unlinked cases of community-acquired SARS were reported in Guangdong, the province in China where SARS first emerged. The source of infection for these cases was not conclusively determined but is presumed to have been wild animals, possibly those in live-food markets.

Clinical Presentation

Following an incubation period of 2-10 days (median 5), the illness typically begins with fever, which is often high (>38°C) and is associated with other constitutional symptoms, such as headache, malaise, myalgia, chills, and rigors. After 3-7 days, lower respiratory symptoms, such as a dry, nonproductive cough or dyspnea, develop and may be accompanied by or progress to hypoxemia. By day 7 of illness, most SARS patients demonstrate abnormalities on chest radiographs. These abnormalities typically appear as focal interstitial infiltrates and progress to more generalised, patchy, interstitial infiltrates, sometimes appearing as areas of consolidation. Diarrhoea has been reported in 20% to >60% of patients, depending, in part, on when during the course of illness symptoms were assessed. The overall case-fatality rate of SARS is approximately 10%, but fatality rates exceed 50% in persons >60 years of age.

Risk for Travellers

During the spring 2003 outbreak, most travellers were at low risk for acquiring SARS. Those who did become infected usually had another risk factor for SARS infection, such as close contact with a SARS patient in a health-care or household setting, and occasionally they had exposure outside these settings in communities with active SARS transmission. In addition, a few SARS patients may have acquired infection during airplane flights on which an undiagnosed, symptomatic SARS patient was also travelling. When there is no evidence of SARS transmission anywhere in the world, there is essentially no risk of acquiring SARS. In case of a re-emergence of SARS, travellers can get up-to-date information on locations with SARS transmission and ways to decrease their risk of acquiring SARS at CDC's Travellers' Health website: http://www.cdc.gov/travel/.

Although there is no conclusive evidence that direct contact with civets or other wild animals from live-food markets has led to cases of SARS, SARS-CoV has been found in these animals. In addition, some persons working with these animals have had evidence of infection with SARS-CoV or a very similar virus. Therefore, it remains theoretically possible that travellers to China who come in contact with these animals may acquire SARS-CoV infection.

Prevention

On the basis of limited available data, prudent travellers to China will avoid visiting live food markets and having direct contact with civets and other wildlife from these markets.

In case of a re-emergence of SARS, travellers to areas reporting SARS cases should avoid settings where transmission is most likely to occur, such as health-care facilities caring for SARS patients and residences of SARS patients. CDC does not recommend the routine use of masks or other personal protective equipment while in public areas, but it does recommend frequent hand-washing to reduce the risk of transmission.

Treatment

Because the clinical presentation of SARS is compatible with that of other causes of atypical pneumonia, empiric treatment regimens have included several antibiotics to presumptively treat known bacterial agents of atypical pneumonia. No specific treatment with proven efficacy is available for SARS-CoV illness.

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

Bibliography
  • CDC. Public health guidance for community-level preparedness and response to severe acute respiratory syndrome (SARS): Version 2 [monograph on the internet]. Atlanta: CDC; 2004 [cited 2004 Oct 11]. Available from: http://www.cdc.gov/ncidod/sars/guidance/index.htm.
  • Guan Y, Zheng BJ, He YQ, et al. Isolation and characterisation of viruses related to the SARS coronavirus from animals in southern China. Science. 2003;302:276-8.
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  • Olsen SJ, Chang HL, Cheung TY, et al. Transmission of the severe acute respiratory syndrome on aircraft. N Engl J Med. 2003;349:2416-22.
  • Pang X, Zhu Z, Xu F, et al. Evaluation of control measures implemented in the severe acute respiratory syndrome outbreak in Beijing, 2003. JAMA. 2003;290:3215-21.
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- Umesh D. Parashar, Mehran S. Massoudi, Larry J. Anderson

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