What is pneumonia?
Pneumonia is an infection of the lower respiratory tract that can be caused by bacteria, viruses, and fungi. Viral pneumonia occurs when a respiratory virus like influenza or SARS-CoV-2 spreads infection into the lungs. Bacterial pneumonia occurs when certain bacteria—such as organisms that typically colonize in the nose and throat, or atypical bacteria—infect the lungs. Fungi are not contagious and do not usually cause infection in healthy people, but if a patient’s immune system is already compromised, fungal pneumonia can occur.
Pneumonia symptoms and signs include cough, fever, shortness of breath, fatigue, and chest pain. People who are high-risk or who are experiencing severe symptoms, like difficulty breathing or a persistent high fever, should be evaluated by a doctor immediately.