Why Does the Flu Hit in the Winter?

According to Centers of Disease Control (CDC) records, February is most often the height of flu season in the U.S., followed by the month of January. The reasons why flu outbreaks follow the seasons have been a mystery until recent research has shed important new insights.

Lifestyle Factors

• One common theory is that people are indoors and around others more, so the flu spreads more easily. Another is that children return to school in the fall and begin to catch illnesses from each other more often.

Environmental Factors

• Another theory is that immunity is lower during winter. Sunlight stimulates the production of substances that support the immune system; winter's shorter days mean decreased production.

New Discovery

• A recent study by the National Institutes of Health finally provides a more definitive answer. Scientists found that the flu virus developed cold-weather survival techniques. It grows a protective coating, enabling it to live longer and spread more effectively. The study explains that in warmer outdoor temperatures this protective coating melts and the virus does not thrive unless it is inside a living person or animal.

What You Can Do

• Get vaccinated. The CDC estimates that vaccination prevents infection in 70-80 percent of cases. Use cleaner or detergent on surfaces where germs gather (such as countertops and appliances). Wash your hands thoroughly and often. Stay clear of anyone with the flu; a person is contagious while sick and for five to seven days after. Keep yourself healthy. Eat well, exercise, get the sleep you need, and manage stress.

Flu Seasons

• In the northern hemisphere, flu season starts in October and goes through March. The southern hemisphere's season runs from May through September, which is their cooler season.