Medical Health Encyclopedia

Severe acute respiratory syndrome (SARS)

Causes, incidence, and risk factors:

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.

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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 2 and 10 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.

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