Pneumonia is an infection of the lungs with a range of possible causes. It can be a serious and life-threatening disease.
It normally starts with a bacterial, viral, or fungal infection.
The lungs become inflamed, and the tiny air sacs, or alveoli, inside the lungs fill up with fluid.
Pneumonia can occur in young and healthy people, but it is most dangerous for older adults, infants, people with other diseases, and those with impaired immune systems.
In the United States (U.S.), around 1 million people are treated in the hospital for pneumonia each year, and around 50,000 die from the disease.
Here are some key points about pneumonia.
Pneumonia is an infection of the lungs that can cause mild to severe illness in people of all ages.
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