What is the incubation period for the flu virus?

The usual incubation period for the flu virus is one to four days, although the average is about two days, according to the U.S. Centers for Disease Control and Prevention. In most healthy adults, the virus is transmissible for one day before and up to seven days after symptom onset.

People with weakened immune systems and children potentially can infect others for a longer period of time, notes the CDC. In otherwise healthy individuals, most cases of the flu last three to seven days, although the general malaise and cough associated with the flu often lasts for more than two weeks.