I posted what the cdc says about it...if you have the flu there is a sudden onset of symptoms.
Flu Symptoms
Influenza (flu) can cause mild to severe illness, and at times can lead to death. Flu is different from a cold. Flu usually comes on suddenly. People who have flu often feel some or all of these symptoms:
- fever* or feeling feverish/chills
- cough
- sore throat
- runny or stuffy nose
- muscle or body aches
- headaches
- fatigue (tiredness)
- some people may have vomiting and diarrhea, though this is more common in children than adults.
*It’s important to note that not everyone with flu will have a fever.
Signs and Symptoms Cold Influenza (Flu)
Symptom onset with Influenza/Flu- Abrupt
https://www.cdc.gov/flu/symptoms/symptoms.htm