SARS

Severe Acute Respiratory Syndrome (SARS) is a contagious respiratory infection that was first described on February 26, 2003. It was first identified as a new disease by WHO physician Dr. Carlo Urbani, who diagnosed it in a 48-year-old businessman who had traveled from the Guangdong province of China, through Hong Kong, to Hanoi, Vietnam. The businessman died from the illness. Dr. Urbani subsequently died from SARS on March 29, 2003 at the age of 46.

In the meantime, SARS began to spread, and within 6 weeks of its discovery, it had infected thousands of people around the world, including people in Asia, Australia, Europe, and North and South America. Schools had closed throughout Hong Kong and Singapore. National economies were affected. The WHO had identified SARS as a global health threat, and issued an unprecedented travel advisory. But it wasn't clear whether SARS would become a global pandemic, or would settle into a less aggressive pattern.

SARS is a serious form of atypical pneumonia, resulting in acute respiratory distress and sometimes death. It is a dramatic example of how quickly world travel can spread a disease. It is also an example of how quickly a networked health system can respond to an emerging threat.

SARS appears to be caused by a virus or viruses. The first reports from virologists suggested the cause was a new virus in the paromyxovirus family (the same family as RSV, measles, and mumps). Subsequent evidence pointed more strongly to a new member of the coronavirus family (the same family that can cause the common cold). The discovery of these viral particles represents some of the fastest identification of a new organism in history.

SARS is clearly spread by droplet contact. When someone with SARS coughs or sneezes, infected droplets are sprayed into the air. With other coronaviruses, the virus can live on hands, tissues, and other surfaces for up to 6 hours in these droplets and up to 3 hours after the droplets have dried. (Also, with other coronaviruses, re-infection is common.)

While droplet transmission through close contact was responsible for most of the early cases of SARS, evidence began to mount that SARS might also spread by hands and other objects the droplets had touched. Airborne transmission was a real possibility in some cases. Live virus had even been found in the stool of people with SARS.

Preliminary estimates are that the incubation period is usually between 2 and 7 days, although there have been documented cases where the onset of illness was considerably faster or slower. People with active symptoms of illness are clearly contagious, but it is not known how long contagiousness may begin before symptoms appear or how long contagiousness might linger after the symptoms have disappeared.