Can a Humidifer a Day Keep the Flu Bugs Away?
A fascinating new study suggests that a simple humidifier might help protect your family from the flu. The air we breathe tends to be quite dry in winter, especially in centrally-heated indoor living spaces. Summertime relative humidity often exceeds 60%, but levels below 30% are commonplace in winter.
Influenza is seasonal; in the Northern hemisphere it peaks every year in mid-winter. (When was the last time you heard of anyone getting the flu in summer?) Some scientists have theorized that the seasonal drop in vitamin D levels, caused by weak winter sunlight, might explain the seasonality of influenza infection. Now, new research suggests that one of the reasons the flu is a wintertime threat almost certainly has to do with the relative lack of moisture in wintertime air.
Researchers at the Centers for Disease Control rigged up a fascinating experiment to test the infectivity/humidity hypothesis. Mannikins in enclosed, climate-controlled rooms stood in for humans, spewing out the influenza virus while “coughing”. Under low-humidity conditions (23% relative humidity, or lower), up to 77% of the virus remained infective for one hour. But when the room air was humidified to about 45% relative humidity (a level attainable with programmable home humidifiers) only about 20% of the virus particles remained infective after an hour. The majority of virus particles lost their infectivity within 15 minutes.
Noti JD, Blachere FM, McMillen CM, Lindsley WG, Kashon ML, Slaughter DR, et al. High humidity leads to loss of infectious influenza virus from simulated coughs. PLoS One. 2013;8(2):e57485. doi: 10.1371/journal.pone.0057485. Epub 2013 Feb 27.