Flu spreads faster at cold temps and dry humidity

William Atkins
Monday, 22 October 2007 06:42

Science - Health

Seasonal flu has been long blamed on such things as being indoors in cold weather, low immune system, humidity, temperature, and ultraviolet radiation. For the first time, researchers directly tested the hypothesis that weather conditions, specifically low temperatures and relative humidity, spreads flu faster than at high temperatures and relative humidity.      

According to an October 18, 2007 study in the journal PLoS Pathogens, the researchers performed twenty experiments at relative humidity levels from 20 to 80%, and at temperatures of 41, 68, and 86 degrees Fahrenheit (5, 20, and 30 degrees Celsius).

They found that low (dry) relative humidity in the range of 20 to 30% produced the spread of the flu (influenza) virus faster than at relative humidity in higher percentages. In fact, at a humidity of 80% of above, their research found no spread of the flu.

With respect to temperatures, the researchers, who are based at the Mount Sinai Medical School of Medicine, found that the flu virus spread the fastest at 41 degrees Fahrenheit (5 degrees Celsius) and the slowest at 68 degrees Fahrenheit (20 degrees Celsius). At 86 degrees Fahrenheit (30 degrees Celsius), there was no transmission of the virus.

The researchers, headed by Dr. Peter Palese, used guinea pigs in the experimental study. They contend that indoor heating and winter temperatures area the major factors in the spread of the flu (influenza).

The other researchers include Anice C. Lowen, Samira Mubareka, and John Steel. The article is titled “Influenza virus transmission is dependent on relative humidity and temperature.”

In an average year within the United States, over 40,000 people die from the flu.