Pneumonia is an infection of the small air sacs of the lungs (alveoli) and the tissues around them.
Pneumonia is one of the most common causes of death worldwide.
Often, pneumonia is the final illness that causes death in people who have other serious, chronic diseases.
Some types of pneumonia can be prevented by immunization.
In the United States, about 2 to 3 million people develop pneumonia each year, and 60,000 of them die. In the United States, pneumonia, along with influenza, is the eighth leading cause of death and is the leading infectious cause of death. Pneumonia is the most common cause of death among infections that develop while people are hospitalized and is the most common overall cause of death in developing countries. Pneumonia is also one of the most common serious infections in children and in infants, with an annual incidence of 34 to 40 cases per 1,000 children in Europe and North America.