Influenza, more commonly known as flu, is an infectious disease caused by a virus. The incubation period, the time of exposure to the flu virus to when you start showing symptoms, is approximately 2 to 5 days.
This varies depending on the exact strand of flu. The incubation period is normally anywhere from one to five days. The average period is around 2 days. Children can remain infectious for up to 10 days after the first symptoms are shown.