Study: SARS Virus Can Spread Through Air'

April 22, 2004
By Rob Stein
Washington Post Staff Writer

The SARS virus apparently can spread distantly through the air in some circumstances, suggesting the deadly lung infection can be transmitted more easily than had been thought, researchers reported yesterday.

A new analysis of an unusual SARS outbreak in a Hong Kong apartment complex last year concluded the virus probably infected hundreds of people by traveling through one building's air shaft before being carried to neighboring towers by the wind.

"Airborne spread of the virus appears to explain this large community outbreak of SARS, and future efforts at prevention and control must take into consideration the potential for airborne spread of this virus," wrote Ignatius T.S. Yu of Prince of Wales Hospital in Hong Kong and colleagues in today's issue of the New England Journal of Medicine.

Other experts agreed the analysis provided a plausible explanation for the incident at the Amoy Gardens housing complex and could account for several other situations in which numbers of people became infected without close direct contact with a sick person, including outbreaks in a Hong Kong hotel, a Toronto hospital waiting room and at least one on an airplane.

"It's something that's been on our radar as something that's plausible," said Umesh Parashar, lead medical epidemiologist for the SARS task force of the Centers for Disease Control and Prevention. But Parashar and other experts said last year's outbreak showed that most infections occurred among people who had close physical contact -- primarily family members and medical workers caring for patients.

"It was a peculiar event," Parashar said. "In most instances, you do require close contact with a person with SARS."

Even if SARS can be transmitted through the air, recommendations to quickly isolate victims in the event of a new outbreak would be effective in containing the virus, he said.

The findings do suggest officials might consider shutting down ventilation systems in buildings where outbreaks occur, said Babatunde Olowokure, a medical officer with the World Health Organization's Global Outbreak Alert and Response Network.

More than 8,400 people in 29 countries contracted SARS -- severe acute respiratory syndrome -- and more than 900 died after the previously unknown lung infection emerged in southern China last year. The disease triggered a worldwide health emergency that restricted international travel, shaking the economies of several Asian nations and Canada.

One of the most puzzling and alarming clusters occurred at Amoy Gardens, where more than 300 residents became infected after a sick man used a resident's bathroom.

Some health officials initially speculated that the virus might have been spread by rodents.

A WHO investigation blamed the outbreak primarily on the complex's malfunctioning plumbing system.

In the new research, Yu and his colleagues conducted a detailed computer analysis of the patterns of where and when people became infected, the ventilation and plumbing systems at the complex and air currents in and around the apartment buildings.

The virus probably traveled out of the bathroom the sick man used through an air shaft, infecting people in other apartments in that building, before being wafted by a northeast wind to neighboring buildings, where it entered their air shafts, the researchers concluded.

http://www.washingtonpost.com/wp-dyn/articles/A32285-2004Apr21.html