Diarrhea
Here is one early sign of flu that no one wants to get. Diarrhea can happen for a number of reasons, whether it is because a meal did not agree with you or you regularly suffer from digestive issues, like irritable bowel syndrome (IBS). Or, you could be coming down with a case of the flu.
Keep in mind that you will not be getting just diarrhea when you have the flu, so be aware of any other signs from his list. If you are not experiencing any other flu-related symptoms, a sudden occurrence of diarrhea can be hinting to other things. See a doctor if your diarrhea does not improve.
