Pneumonia is an inflammatory illness of the lung. Frequently, it is described as lung parenchyma/alveolar (microscopic air-filled sacs of the lung responsible for absorbing oxygen from the atmosphere) inflammation and (abnormal) alveolar filling. Pneumonia can result from a variety of causes, including infection with bacteria, viruses, fungi, or parasites, and chemical or physical injury to the lungs. Its cause may also be officially described as idiopathic, that is unknown, when infectious causes have been excluded. ...

Pneumonia is an inflammatory illness of the lung. Frequently, it is described as lung parenchyma/alveolar (microscopic air-filled sacs of the lung responsible for absorbing oxygen from the atmosphere) inflammation and (abnormal) alveolar filling. Pneumonia can result from a variety of causes, including infection with bacteria, viruses, fungi, or parasites, and chemical or physical injury to the lungs. Its cause may also be officially described as idiopathic, that is unknown, when infectious causes have been excluded.
Typical symptoms associated with pneumonia include cough, chest pain, fever, and difficulty in breathing. Diagnostic tools include x-rays and examination of the sputum.
Pneumonia is a common illness which occurs in all age groups, and is a leading cause of death among the elderly and people who are chronically and terminally ill. Vaccines to prevent certain types of pneumonia are available. The prognosis depends on the type of pneumonia, the appropriate treatment, any complications, and the person's underlying health.