February 10, 2009

Humidity Could Help Fight Flu Virus

It has been known that the influenza virus flourishes in dry air.

However, new research notes that a key to prevention is complete humidity, not the normally touted relative humidity.

Relative humidity differs depending on the air temperature; absolute humidity simply does not, says the report published on Tuesday in Proceedings of the National Academy of Science.

"The correlations were surprisingly strong. When absolute humidity is low, influenza virus survival is prolonged and transmission rates go up," said Jeffrey Shaman, an atmospheric scientist who focused on the connections between climate and the disease.

The result "is very important for the scientific community and the medical community to know to develop better prediction models of influenza," Shaman told the Associated Press.

The findings offers a "more elegant explanation for why we see these seasonal spikes" in flu. He added that it indicates that may be worth your time to add humidity to the air, like keeping a kettle or a pot of water on the stove. However, too much humidity can lead to issues like mold.

The connection between flu and low humidity is relevant because in winter weather, even a high relative humidity reading could show very little present moisture in the air. The less moisture present, the more the flu virus seems to flourish.

Shaman and co-author Melvin Kohn reviewed data from research released in 2007 in the journal PLoS Pathogens by researchers at Mount Sinai School of Medicine in New York. The numbers discovered that more flu cases were present when it was both colder and drier.

In their report, Shaman and Kohn think that utilizing absolute humidity could explain the 50 percent of influenza spreading around and also the 90 percent of virus endurance.

Generally speaking, humidity can be misleading.

More moisture can flourish more in warm air than in chilly air. Many think that warmer air has more moisture than frosty air. Even though it is not scientifically accurate, it is a simple way of pondering it.

Warm air actually has 30 percent relative humidity and cold air has 60 percent relative humidity, and the latter may have the same amount of moisture.

So, even though cold air sounds damp, it is dry, which is what the flu enjoys.

"In some areas of the country, a typical summer day can have four times as much water vapor as a typical winter day - a difference that exists both indoors and outdoors," Shaman said. "Consequently, outbreaks of influenza typically occur in winter when low absolute humidity conditions strongly favor influenza survival and transmission."


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