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