Influenza (flu) is a contagious respiratory infection that circulates around the world each year and usually hits the United States between October and May. The viruses that cause the flu are most often spread by coughing, sneezing, or close contact.
Anyone can get the flu. According to the Centers for Disease Control and Prevention (CDC), it tends to strike suddenly and can last for several days. Although it has some of the same symptoms as the common cold—a runny or stuffy nose, cough, sore throat, and fatigue—the flu can lead to pneumonia, blood infections, or even death. Other symptoms of the flu include fever, body aches, headache, and chills.