Stomach pain, nausea, and fever are caused by gastrointestinal flu, bacterial dysentery, and food accumulation, etc. First of all, gastrointestinal flu is a cold disease caused by viruses entering the intestinal tract and invading the intestinal system. The virus also affects the immune system, so many people have fever. Secondly, dysentery is a disease caused by dysentery bacillus infection, which causes necrosis of the intestinal mucosa and the function of the intestinal tract, and during the disease, in addition to diarrhea, patients will also have symptoms such as stomach pain, nausea, vomiting, etc. Some people will have fever because of a large loss of water in the body. Lastly, pent-up food is especially common in children, mainly due to weakness of the spleen and stomach and lack of intestinal power. When there is pent-up food, the patient will not only have nausea, vomiting, stomach discomfort, but also low fever because of the prolonged stagnation of food and the resulting heat.