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June/July 2013 (vol. 10/1)

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Research Plus

Greater flu risk at lower humidity

Maintaining relative humidity (RH) above 40% reduces the infectivity of airborne influenza virus in medical examination rooms, according to this laboratory simulation study. Live N1N1 flu virus was nebulised and pumped (to mimic a patient coughing) from a laboratory manikin in a sealed simulated examination room. A breathing simulator was attached to a second manikin, which acted as a surrogate healthcare worker. Air samplers were attached to and around the second manikin’s mouth, and elsewhere in the room. RH was adjusted from 7% to 73%. The total amount of virus collected at 15-minute intervals up to one hour was approximately the same, regardless of RH; however, it retained 71%–77% infectivity at RH ≤23% but only 15%–22% infectivity at RH ≥43%, with most of the infectivity lost during the first 15 minutes. Maintaining higher RH can reduce infection risk, and this should be considered when building healthcare facilities.


PLoS One 2013; 8(2): e57485


Occupational Health at Work June/July 2013 (vol. 10/1) pp41