A team of researchers from Mount Sinai Medical College, New York, discovered why the flu spreads mainly in winter time.

Apparently the virus is more stable in the cold and dried air.

Dr. Peter Palese, chairman of the microbiology department at Mount Sinai Medical College and leader author of the medical study, said: “Influenza virus is more likely to be transmitted during winter on the way to the subway than in a warm room,” the New York Time reports.

Dr. Palese conducted a study on guinea pigs because he found that the animal is good at spreading the virus. He published his results in the October 19 issue of PLoS Pathogens.

Many people have asked themselves why flu comes in winter time. Some said that it could be the lower immunity resulted from the decrease of natural production of vitamin D when days are shorter, or the crowds in the subway, or the children at school who are kept in closed spaces in winter time getting the flu and spreading it at home.

In northern latitudes the flu season is from November to March, the coldest months. From May to September the flu season appears in the southern latitudes, while in the tropics there is no real flu season as it isn’t any flu at all.

According to Dr. Palese, the guinea pigs were exposed to the virus and then varied the temperature and humidity in their habitat.

He discovered that the virus was spreading mostly at temperatures of 41 degrees and as the temperature rose, it declined. At 86 degrees the virus wasn’t spreading at all.

Regarding the humidity, the virus spread excellent at a low humidity, 20 percent, and at 80 percent it stopped spreading at all.  

Dr. Palese says that the flu virus spreads in the winter, through the air, rather than in a warm room.

According to him, the flu virus is more stable in cold air. The virus particles remain in the air, floating in little respiratory droplets, when there is low humidity.

The answer to the question of “how can we avoid it ?” is not by staying in a greenhouse all winter, but getting a flu shot.