Airborne flu viruses threaten health workers,
Sep 29, 2006 (CIDRAP News) – "A microbiologist who reviewed the evidence about how influenza viruses spread says that some official guidelines, including the US pandemic influenza plan, may not go far enough in protecting healthcare workers who take care of flu patients.
Writing in Emerging Infectious Diseases, Dr. Raymond Tellier of the University of Toronto says there is good evidence that flu viruses often spread via tiny airborne particles, despite a common belief that they travel mainly in large droplets that quickly fall to the ground after a flu patient coughs or sneezes.
Good protection from airborne particles requires the use of an N95 respirator. Yet the US, Canadian, and British pandemic flu plans advise healthcare workers to use simple surgical masks, which are much less effective, Tellier contends.
"Compelling evidence in the literature indicates that aerosol transmission of influenza is an important mode of transmission, which has obvious implications for pandemic influenza planning, and in particular for recommendations about the use of N95 respirators as part of personal protective equipment," he writes.
"Airborne particles" are usually defined as particles about 5 microns or less in diameter, Tellier says. Particles larger than about 10 to 20 microns fall quickly to the ground, while those smaller than 3 microns essentially do not settle. Coughing and sneezing generate particles in a range of sizes, many of them small enough to stay airborne for a long time. Airborne particles can penetrate into the lungs, whereas the larger particles and droplets are more likely to be trapped in the upper respiratory tract."...
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