Pneumonia is an inflammation of your lungs, usually caused by infection. Bacteria, viruses, fungi or parasites can cause pneumonia. Pneumonia is a particular concern if you're older than 65 or have a chronic illness or impaired immune system. It can also occur in young, healthy people.

Pneumonia can range in seriousness from mild to life-threatening. Pneumonia often is a complication of another condition, such as the flu. Antibiotics can treat most common forms of bacterial pneumonias, but antibiotic-resistant strains are a growing problem. The best approach is to try to prevent infection.