Influenza can cause diarrhea, but this is a minority occurrence. Influenza is a disease that appears after the respiratory system of a human body gets infected with the influenza virus. After infecting the human body, influenza primarily manifests symptoms like coughing, sore throat, and fever. However, some patients may develop gastrointestinal symptoms such as diarrhea, nausea, and vomiting after being infected with influenza. This situation is related to viral infection, not the commonly thought stomach flu or food poisoning. Some patients may also experience joint pain and a decrease in appetite. If a patient experiences diarrhea accompanied by respiratory infection symptoms and has tested positive for influenza antibodies, it is necessary to promptly use antiviral drugs for influenza. However, many doctors who do not have such experience in diagnosing influenza might mistake the nausea and diarrhea caused by influenza for gastroenteritis, leading to a delay in proper treatment. Therefore, if one has respiratory symptoms accompanied by gastrointestinal symptoms, the possibility of influenza should be considered.