Patients with pneumonia may have neither cough nor fever, especially children and elderly people who may have atypical symptoms, such as abdominal pain and diarrhea, while some patients may only have poor mental health, and some patients may have nausea, vomiting, loss of appetite, and general lethargy. These patients may not go to the respiratory department first, but often go to the gastroenterology department, and after examination, they are finally found to have a lung infection. Therefore, if you have symptoms such as mental lethargy, loss of appetite, abdominal pain, or diarrhea, you should also be on the alert for pneumonia.