FollowingUnfollow SUCCESS! FollowingUnfollow. cspencer. 5 Answers. 85 Helpful Votes. A. It takes approximately 24-48 hours for initial symptoms to appear after exposure to the influenza virus. If you suspect you have the flu, seek medical treatment quickly.Tamiflu, if taken within the first 48 hours of symptoms occurring, can reduce the time it takes to heal and can reduce symptoms.ollowingUnfollow SUCCESS! FollowingUnfollow. cspencer. 5 Answers. 85 Helpful Votes. A. It takes approximately 24-48 hours for initial symptoms to appear after exposure to the influenza virus. If you suspect you have the flu, seek medical treatment quickly.