Pneumonia

Pneumonia is an inflammatory condition of the lung—affecting primarily the microscopic air sacs known as alveoli. It is usually caused by infection with viruses or bacteria and less commonly other microorganisms, certain drugs and other conditions such as autoimmune diseases.

Typical symptoms include a cough, chest pain, fever, and difficulty breathing. Diagnostic tools include x-rays and culture of the sputum. Vaccines to prevent certain types of pneumonia are available. Treatment depends on the underlying cause. Presumed bacterial pneumonia is treated with antibiotics. If the pneumonia is severe, the affected person is generally admitted to hospital.

Pneumonia affects approximately 450 million people a year and results in about 4 million deaths (7% of the world's total). Although pneumonia was regarded by William Osler in the 19th century as "the captain of the men of death", the advent of antibiotic therapy and vaccines in the 20th century has seen improvements in survival. Nevertheless, in developing countries, and among the very old, the very young and the chronically ill, pneumonia remains a leading cause of death.