The duration of viral flu, also known as influenza, can vary depending on the individual and the strain of the virus. In general, the flu lasts for about one to two weeks. The symptoms of the flu can include fever, sore throat, runny or stuffy nose, body aches, and headache.   The most severe symptoms usually occur during the first three to five days, and then gradually improve over the next week or two. However, some people may continue to feel tired and weak for several weeks after the flu has resolved. Those with pre-existing medical conditions, such as heart, liver, or lung disease, may find symptoms of the flu to be more severe and long-lasting. If you have any concerns about the duration or severity of your symptoms, it is best to consult with a healthcare provider.