Pneumonia is an infection of the lungs. It usually starts as an infection in the upper respiratory tract (nose and throat) and develops when fluid collects in the lungs. The congestion makes it difficult to breathe.

The infection can be caused by various microorganisms such as viruses, bacteria or fungi. Factors that increase the risk of pneumonia include premature birth, second-hand smoke, asthma, sickle-cell anemia (abnormally shaped oxygen-carrying blood cells), heart defects, weak immune system, poor nutrition status or spending time in crowded places.

Symptoms of pneumonia include chills, cough, fever, nasal congestion, rapid breathing, wheezing, vomiting, chest pain, abdominal pain, decreased activity, pale or bluish nails and lips, and loss of appetite. The condition is diagnosed with blood tests, chest X-ray and sputum culture.

Pneumonia is treated with antibiotics. If your blood oxygen level is lower than normal, your doctor will place an oxygen mask or tube in your nostrils to facilitate breathing. Some types of pneumonia can be prevented with a vaccine.