Fever and diarrhea may be caused by acute gastroenteritis or viral infection with fever, and it is recommended to treat the symptoms in conjunction with the symptoms under the guidance of a doctor. 1. Acute gastroenteritis: Severe gastroenteritis will cause the body to develop an immune response and show symptoms of fever. As the intestines are infected by bacteria or viruses, it will lead to congestion of the gastrointestinal mucosa causing reduced digestive ability and symptoms of diarrhea. 2. Viral infections: viral infections can cause the body to develop an immune response, further symptoms of fever, fever at the same time the body will also release inflammatory factors, inflammatory factors will lead to gastrointestinal dysfunction symptoms of diarrhea. Acute gastroenteritis and viral infections can cause fever and diarrhea, it is recommended to go to the hospital to determine the cause of the disease, under the guidance of the doctor for treatment.