Healthwise

Typical flu presents with sudden onset fever, chills, diffuse body aches, cough and significant fatigue. The incubation period is usually about 3 to 5 days after you have been exposed. The usual duration is around 7 days, but one can feel weak and tired for longer than that. Usually if you have a normal immune system and no significant chronic illness, symptomatic treatment is all that is needed. Your immune system will eliminate the virus. Sometimes there can be complications like a secondary bacterial bronchitis or pneumonia. If you are becoming worse rather than better after 7 days, it is reasonable to see a doctor.

People who are immune compromised or have chronic medical problems, like those over 65, young children below 5, pregnant females, and those with chronic conditions like COPD, cancer, heart trouble, asthma, are more likely to get complications after getting the flu. It is reasonable for them to see a doctor as soon as flu is suspected since it might be reasonable to treat them for flu.