The flu season is in full swing from November to March, and there are some interesting facts that you might not know about the illness. About 20 percent of people in the country suffer from the flu each year. The elderly and children often see the worst symptoms with about 5 million people experiencing severe cases of the illness. Not all flu vaccines work each year. All it takes is for a strain to mutate ever so slightly for the vaccine not to work or for the illness to make more people sick than in other seasons. Even though a test may indicate that you don’t have the flu, it’s still possible to have the virus. If the virus is in the early stages, then it sometimes won’t be picked up by a test. It’s important to take flu medications within the first 24 hours of being diagnosed or exhibiting symptoms as most prescription medications won’t work once the virus has taken over the body. The flu virus usually lingers for about two days, but the symptoms that you experience might last for several days or even a few weeks depending on your immune system and other illnesses that you have.