An inflammation of the lungs that's usually caused by infection with bacteria, viruses, fungi or other organisms.
Pneumonia is a particular concern for older adults and people with chronic illnesses or impaired immune systems, but it can also strike young, healthy people. Worldwide, it's a leading cause of death in children.
There are many kinds of pneumonia ranging in seriousness from mild to life-threatening. Pneumonia acquired while in the hospital can be particularly virulent and deadly. Although signs and symptoms vary, many cases of pneumonia develop suddenly, with chest pain, fever, chills, cough and shortness of breath. Infection often follows a cold or the flu, but it can also be associated with other illnesses or occur on its own.