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Studies Confirm Likely Cause of SARS

New Coronavirus Never Before Seen in Humans

WebMD Health News

April 10, 2003 -- Investigators are nearly certain that a previously unknown form of a coronavirus is the major cause of SARS (sudden acute respiratory syndrome), and new research rushed for release today backs up their argument with near conclusive scientific evidence.

"While we are increasingly confident that we are dealing with a new coronavirus, we cannot yet say that this is the definitive cause of SARS," says CDC Director Julie Gerberding, MD, in a briefing today.

To definitively prove this novel coronavirus is the cause of SARS, infectious disease experts say they still need to show two things:

  • They must unequivocally show that the coronavirus is present in the lung at the same time pneumonia develops.
  • An animal model of SARS must be developed in which they infect an animal with the coronavirus, the animal becomes sick with pneumonia, and the virus is then isolated from the lung tissue of the animal.

In addition, further studies are needed to determine the role other viruses or illnesses play in SARS, especially in promoting severe forms of disease. (Currently, about 10% of SARS patients develop a particularly serious and potentially life-threatening form of the disease and the other 90% have a milder form.)

If and when the new coronavirus is confirmed as the cause of SARS, Gerberding says it will take at least a year to develop an experimental vaccine to combat the virus.

SARS still spreading, but no U.S. deaths

As of today, the WHO says 2,627 probable SARS cases have been reported worldwide, plus 166 suspected SARS cases in the U.S. across 30 states, which are currently under investigation by the CDC.

Gerberding says of the suspected U.S. SARS cases, 60 people have been hospitalized, four are currently hospitalized, 33 developed pneumonia, and one required a ventilator to breathe.

According to worldwide statistics, about 4% of SARS patients die, but so far no SARS deaths have been reported in the U.S.

Gerberding says that might be due to a combination of very good luck as well as several other factors. First, the U.S. had the advantage of recognizing SARS after watching the epidemic develop in Asia, which allowed the healthcare system to activate appropriate measures to control the disease's spread.

Second, it is also possible this country hasn't seen a so-called "super-spreader" of SARS. Evidence from the disease outbreaks in Hong Kong and Canada suggests that some people are particularly effective at transmitting the disease for unknown reasons.

Finally, the CDC is using a different and broader definition of SARS cases that it reports to the WHO compared with other countries. The agency reports "suspected" SARS cases that meet criteria according to symptoms and travel history and are currently under investigation rather than the "probable" case definition used by other countries.

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