2024 Flu Symptoms And Duration Of Illness. Flu symptoms usually appear two to three days after contact with the virus, according to the university of pennsylvania health system, but you may start to feel sick. Learn about flu risks, vaccination, prevention strategies, and how to manage symptoms effectively with this comprehensive flu season guide.

Flu can cause mild to severe illness, and at times can lead to death. Fever, vomiting, cough, and rhinorrhea (runny nose).