Pneumonia is an inflammation of the lungs most often caused by infection with bacteria or a virus. Pneumonia can make it hard to breathe because the lungs have to work harder to get enough oxygen into the bloodstream.

Symptoms of pneumonia caused by bacteria often begin suddenly and may follow an upper respiratory infection, such as influenza (flu) or a cold. Common symptoms include fever, a cough that often produces colored mucus (sputum) from the lungs, and rapid, often shallow breathing.

Older adults may have different, fewer, or milder symptoms. The major sign of pneumonia in older adults may be a change in how well they think (confusion or delirium) or a worsening of a lung disease they already have.

Symptoms of pneumonia not caused by bacteria (nonbacterial) include fever, cough, and shortness of breath, and there may be little mucus production.

Antibiotics are used to treat pneumonia caused by bacteria.