Pneumonia is an infection of the lungs that may be caused by bacteria, viruses or fungi. Pneumonia symptoms may vary depending on the cause of the infection, but can include fever, chills, cough, pain in the chest when breathing or coughing, fatigue, nausea or diarrhea. People who are at a higher risk for serious complications from pneumonia should seek immediate treatment from a qualified physician when such symptoms occur. This particularly applies to children aged two and younger; adults aged 65 and up; those with compromised immune systems heart problems or lung conditions; and people who are undergoing immunosuppressive therapy. You should see a doctor if you have a fever over 102° F for several days, persistent and productive cough, difficulty breathing or chest pain. A vaccine may help prevent some kinds of pneumonia.