The winter cold hitting across the United States provides the perfect temperature for the flu virus to spread, according to the National Institute of Health.
Researchers suggest that under cold and dry conditions that come along with the winter season, the flu virus' outer coating hardens, allowing the flu virus particles to travel through the air and spread easily among people, according to Live Science.
During the winter, the flu virus particles can also remain alive for longer periods of time and travel for longer distances, too.
At higher temperatures the outer coating, which is like a protective gel, melts away to a liquid phase which is not strong or protective enough to allow the virus to survive, much less travel and spread, according to Live Science.
Flu season begins as early as October but peaks December through February, the Center for Disease Control and Prevention reported. Depending on temperatures, the virus can keep spreading until May.
During the cold months, people also spend more time indoors, or in closed spaces with other people, giving many more opportunities for the already empowered virus to spread, Live Science reported.
In September, even though its a month before the flu season, children begin attending school again, raising the chances of coming into contact with other kids who will catch the flu virus and take it home, Dr. Bruce Lee, an associate professor at the University of Pittsburgh Graduate School of Public Health, told Live Science in a 2012 interview.
