Gastrointestinal flu is caused by a viral infection, commonly seen in the summer and fall seasons, and its symptoms often include those of both upper respiratory tract infections and acute gastroenteritis. Symptoms of upper respiratory infection include fever, chills, dizziness, headache, fatigue, general muscle pain, sore throat, cough, etc.; symptoms of acute gastroenteritis are vomiting, diarrhea, abdominal bloating, abdominal pain, etc., often presenting as watery stools. This disease can be diagnosed through routine blood tests and stool exams, which help distinguish it from bacterial infections causing diarrhea. Treatment typically involves oral antiviral medications and anti-diarrheal drugs.