Report: SARS Can Spread Through Air
Virus-Laden Plume Spread SARS in 2003 Hong Kong Outbreak
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Detective Work Pays Off continued...
"Virus laden aerosols generated in the [drainage pipes] of unit 7 in building E returned to the bathroom through the dried-up seals of the floor-drain traps and then entered the air shaft, probably by means of suction created by an exhaust fan. The aerosols moved upward owing to the buoyancy of the warm, humid air within the airshaft and could enter apartment units that bordered the airshaft on the upper floors because of the negative pressure created by the exhaust fans or the action of wind flows around the building. The horizontal spread of infection to other units in building E was by movement of the air between apartment units. After the plume reached the top of the air shaft in building E, the virus was spread to some units at certain heights in buildings B, C, and D by the action of a predominant northeasterly wind."
Over the next few days, 187 people from the apartment complex came down with SARS.
Airborne SARS -- and Flu?
This scenario does not mean that SARS necessarily spread though the air in explosive outbreaks, note Chad J. Roy, PhD, MSPH, and Donald K. Milton, MD, DrPH, in an editorial accompanying the Yu report. Roy is with the U.S. Army Medical Research Institute of Infectious Diseases; Milton is with the Harvard School of Public Health.
Indeed, they say, less infectious patients likely spread the virus through droplets as has commonly been thought.
But with the advantage of hindsight, it does seem likely that some SARS cases spread through the air. And as public schools are poorly ventilated, Roy and Milton note that it's lucky SARS never spread among children.
In the next epidemic -- possibly the next major flu epidemic -- we may not be so lucky.
"The reduction of airborne transmission of influenza by means of air sanitation in schools could prove important with the emergence of the next pandemic influenza virus," they write. "[The Amoy Gardens scenario] may be a harbinger of unorthodox transmission patterns associated with emerging infectious agents in the modern built environment."