SARS found spread by air

Discovered in patient's hospital rooms in 2003 outbreak
Study shows disease could be more contagious than thought

AElaine Carey
Medical Reporter

A new Toronto study had found evidence that the SARS virus may spread through the air, not just human contact, making it far more contagious than previously thought.

Following testing, scientists detected the SARS coronavirus in the air in one of four hospital rooms that was occupied by patients with the disease, says the study published in the May issue of the Journal if Infectious Diseases , released yesterday by the Infectious Diseases Society of America.

That could explain how air travelers in Asia and people in adjacent apartment buildings in Hong Kong contracted it even though they had no direct contact, said Timothy Booth, a virologist at the Public Health Agency of Canada laboratory in Winnipeg, who led the study.

"It does show SARS is in the air and if you're in the same room with a patient, you might get enough to infect you if you were not wearing a mask," he said in an interview.

The scientists also found the virus on a television remote control, a bed table and a refrigerator door in a nurses' station. Although it wasn't viable, it illustrates the need for strict infection-control procedures, the study says.

An editorial accompanying the study called it "important work" that shows "beyond doubt" that SARS can spread through breathing the same air as a patient.

Until now, researchers have maintained that the virus spreads only through direct contact with infected water droplets, which can occur when a patient coughs.

The study concludes that severe acute respiratory syndrome is an "opportunistic airborne infection," in the same class as the common cold.

That makes it far less viable than an influenza virus, Booth said, but more easily spread than through direct contact with a patient who is coughing or sneezing.

Every person who gets the flu spreads it to 10 others, while every patient who gets an opportunistic infection spreads it to only one or two others, he said.

"If SARS had been like the flu, we would have had a big problem," Booth said. "But the whole question of airborne transmission scares people."

Saying a virus is airborne "has huge political implications," said Dr. Allison McGeer, head of infection control at Toronto's Mount Sianai Hospital, because of public panic that can result.

But the study cautions that just because the virus is in the air isn't proof that it could spread that way. Although it has long been suspected, there is no documented case of a patient getting airborne SARS.

It concludes that in the event of another SARS outbreak, hospitals should carefully screen their building ventilation rates and the efficiency of air-filtration systems in isolation rooms.

About 8,098 people in 29 countries contracted the virus in 2003 and 774 of them died, including 44 in the Toronto area.

After it petered out, the World Health Organization concluded there was no evidence to suggest that SARS is an airborne virus, like influenza, tuberculosis and chickenpox.

But despite following strict infection-control precautions, health-care workers continued to get the virus, leading researchers to wonder if it was spreading through other means.

Wearing a mask would protect health-care workers, but they would need to be extremely careful in taking it off and those precautions weren't always taken, Booth said.

The finding justify those who are committing resources to provide a safer hospital environment and "might provide the needed pressure for others to follow suit," the journal's editorial says.

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