Influenza, also called the flu, is a contagious viral infection that affects the nose, throat, and lungs. It spreads easily through droplets from coughing or sneezing and causes fever, cough, sore throat, fatigue, and body aches. While most people recover within a week, severe cases may lead to complications. Annual vaccination, good hygiene, and early treatment help prevent influenza, protect high-risk groups, and keep you healthy during the flu season.