This is one of three Journal Notes this week that will discuss severe acute respiratory syndrome (SARS).

Severe acute respiratory syndrome (SARS) is believed to have originated in the Guandong Province of China in late 2002. By March 2003, the illness—which is characterized, in part, by a fever greater than 100.4 degrees Fahrenheit, a dry cough, body ache, and trouble breathing—had spread to Vietnam, Hong Kong, and Canada. To date, according to the World Health Organization, 7699 probable cases of SARS have been reported worldwide.

Many cases of SARS have been linked back to a health care worker from the Guandong Province in China who visited and was hospitalized in Hong Kong. Although at first the cause was a mystery, the likely agent responsible was ultimately identified with unprecedented speed and scientific cooperation. In a study published in the May 15, 2003 New England Journal of Medicine , scientists discuss the efforts of the US Centers for Disease Control and Prevention (CDC) to nail down the likely cause of SARS—a previously unrecognized coronavirus.

About the Study

Health professionals around the world have collaborated to determine the cause of SARS. Autopsy specimens and clinical samples of the blood, serum, and airway secretions of affected patients have been sent to the CDC from Vietnam, Singapore, Thailand, Hong Kong, Canada, Taiwan, and the United States. Using these samples, researchers used sophisticated equipment and techniques to identify a range of potential agents responsible for SARS and to narrow the range down to the most likely candidate.

The Findings

A previously unidentified virus was isolated from a patient who met the case definition for SARS. Examination with an electron microscope revealed that this virus had features characteristic of coronaviruses. The virus, for example, was found to react to coronavirus antibodies, and molecular analyses of its RNA gene fragments confirmed that it contained sequences of nucleotides (the building blocks of RNA) that were characteristic of a coronavirus. However, this coronavirus is different than any coronavirus that had been identified before.

Identical nucleotide sequences were found in virus isolated from 12 other probable SARS patients. Antibody tests that provoked reactions from the viruses in these patients confirmed that they were coronaviruses. What’s more, other than one patient who also had a rhinovirus (the most common cold virus), none of the 12 SARS patients tested positive for other respiratory pathogens.

The scientists were not able to identify the SARS-associated coronavirus in all SARS patients, however. Nor were they able to establish a cause and effect relationship between the coronavirus and SARS.

How Does This Affect You?

Coronaviruses are a family of viruses that cause a variety of diseases in humans and animals including gastroenteritis (“stomach flu”) and upper and lower respiratory tract disease. Until now, coronaviruses have only been known to cause mild disease (the common cold) in humans. However, they have long been known to cause more serious disease in animals.

In this study, scientists discovered a strong association between a novel coronavirus and SARS. Presumably, this virus originated in animals and mutated enough to jump to humans. If, as expected, the virus is confirmed as the cause, this would be the first example of a coronavirus that causes severe disease in humans.

The discovery of a SARS-associated coronavirus has many potential benefits. First, once the virus is identified it becomes possible to locate its primary animal sources and eliminate them. (This is how mad cow disease was handled in the United Kingdom a few years ago.) Second, it makes it possible to more quickly and reliably identify patients with the illness, which could reduce the risk of spread if those testing positive are promptly quarantined. Finally, work can begin on a vaccine, in the hopes of slowing, or even ending, the SARS outbreak.