How is lung infection caused?

Lung infection, also known as pneumonia, refers to inflammation of the terminal airways, alveoli and lung interstitium, caused by pathogenic microorganisms, physical and chemical factors, immune damage, allergies and drugs. Bacterial pneumonia is the most common pathogen of pneumonia. Pneumonia can be caused by the following ways: 1. air inhalation;2. blood dissemination;3. spread near the infected site;4. aspiration of bacteria colonized in the upper respiratory tract.