Science Behind the News - Influenza & Flu Vaccines

The flu is a respiratory illness caused by a virus, the smallest and simplest of the pathogens that cause disease in the human body. According to the Centers for Disease Control and Prevention, as many as one in five Americans catch the flu each season, which occurs every winter from about October to March. While there is no cure, understanding what the flu virus is and how it's transmitted can help lessen the impact of the annual flu season.