Pneumonia is a serious infection of the lungs that causes the air sacs in the lungs to fill with pus and other liquid. The infection may be caused by bacteria, viruses, fungi, and mycoplasma. In general, pneumonia is divided into 2 types: community-acquired, or hospital- or nursing home-acquired.


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You may get pneumonia through a simple encounter with an organism that you breathe into your lungs. Whether or not illness occurs depends several factors, including the contagiousness of the organism, the number of organisms that are inhaled, and the ability of the immune system to fight infections.

In the United States, pneumonia is a very common illness, especially among people who are elderly.