The flu (influenza) is a respiratory infection caused by a variety of viruses. This infection is highly contagious; it is spread primarily when an infected person coughs or sneezes. Symptoms of this condition tend to start quickly and can include fever, dry cough, sore throat, and chills.
Most people who get the flu will get better within a week, although they may have a lingering cough and tire easily for a while longer. However, for certain people, such as elderly people or newborn babies, the flu and its complications can be dangerous.
(Click Flu for an in-depth overview of this condition. This article also explains how the flu differs from the common cold and offers statistics on how many people come down with the illness during each flu season.)