Gastrointestinal problems
The flu symptoms, especially in the early stages, can extend below the throat and chest. Some strains of the influenza virus are known can cause stomach problems such as nausea, diarrhea, abdominal pain, vomiting, and diarrhea. Dehydration is a serious complication of flu-related diarrhea and vomiting. You should drink water, fruit juices, soups, and sports drinks to avoid dehydration.