Pneumonia is a serious infection or inflammation of one or both lungs.

Pneumonia is caused by the inhalation of infected microorganisms (tiny, single-celled living organisms, such as bacteria, viruses, fungi or protozoa) spread through contact with an infected person. The microorganisms enter the body through the mouth, nose and eyes. If the body's resistance is down, the natural process of fighting off diseases is weakened and the microorganisms are free to spread into the lungs and the lungs'...