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Humidity vs. The Flu

March 27, 2013

Low humidity may increase the transmissibility of the influenza virus indoors.



Humidity vs. the flu. I’m Bob Hirshon and this is Science Update.

High indoor humidity may cut down on the transmissibility of the influenza virus. This according to researchers at the National Institute for Occupational Safety and Health. They built a simulated examination room to study how the flu virus behaves in healthcare settings. Inside they placed a device that simulates coughing, which they loaded with flu virus, along with a mannequin that simulates breathing. Then they measured how much active virus the mannequin breathed in after simulated coughs at different levels of humidity. Biologist John Noti led the study.

JOHN NOTI (National Institute for Occupational Safety and Health):

What we found was that if you raised the humidity, the infectivity of the virus drastically decreased.


He says below 23% humidity, infectivity remained high, but rapidly plummeted when it topped 40%. He says more testing is needed to find out whether this effect would hold up in everyday settings. I’m Bob Hirshon, for AAAS, the science society.

Click here to read more about the study.

National Institute of Occupational Safety and Health (NIOSH) samplers collected aerosols through the mouth, 10 cm on either side of the manikin’s mouth, and at 3 other positions (P1, P2, P3) as shown. The mouths of the coughing and breathing simulators and sampler inlets at P1, P2, and P3 were located 152 cm above the floor (approximate mouth height of a patient sitting on an examination table and a standing healthcare worker). All dimensions adjacent to white arrows within the room are in centimeters. (Noti, et al. PLOS One, 2/27/13)