SARS

Severe Acute Respiratory Syndrome (SARS) is a serious form of 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.

This contagious respiratory infection was first described on February 26, 2003. SARS was identified as a new disease by World Health Organization (WHO) physician Dr. Carlo Urbani. He 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 was spreading, and within 6 weeks of its discovery, it had infected thousands of people around the world, including people in Asia, Australia, Europe, Africa, 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. Daily WHO updates tracked the spread of SARS seven days a week. It wasn't clear whether SARS would become a global pandemic, or would settle into a less aggressive pattern.

The rapid, global public health response helped to stem the spread of the virus, and by June 2003, the epidemic had subsided to the degree that on June 7 the WHO backed off from its daily reports. Nevertheless, even as the number of new cases dwindled, and travel advisories began to be lifted, the sober truth remained: every new case had the potential to spark another outbreak. SARS appears to be here to stay, and to have changed the way that the world responds to infectious diseases in the era of widespread international travel.

SARS is caused by 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. Like other coronaviruses, the SARS virus may 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.

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, where it has been shown to live for up to four days. And the virus may be able to live for months or years when the temperature is below freezing.

With other coronaviruses, re-infection is common. Preliminary reports suggest that this may also be the case with SARS.

Preliminary estimates are that the incubation period is usually between two and ten 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.

Reports of possible relapse in patients who have been treated and released from the hospital raise concerns about the length of time individuals can harbor the virus.