Pneumonia is an infection of the lungs that is caused by bacteria, viruses, fungi, or parasites. It is characterized primarily by inflammation of the alveoli in the lungs or by alveoli that are filled with fluid (alveoli are microscopic sacs in the lungs that absorb oxygen). The signs of pneumonia come from both the infection and the reaction in the lungs, which intumonia come from both the infection and the reaction in the lungs, which interfeerferes with air flow.
Pneumonia can be very serious, because it directly interferes with your body’s ability to exchange carbon dioxide and oxygen. The severity of pneumonia depends on which organism is causing the infection. Depending on the location of the infection, certain symptoms are more likely to develop.