pneumonia

Inflammation of the lungs, generally due to bacterial or viral infection but also to particulate matter or gases. It is characterized by a build-up of fluid in the alveoli, the clustered air sacs (at the ends of the air passages) where oxygen exchange takes place.

Symptoms include fever and pain in the chest. With widespread availability of antibiotics, infectious pneumonia is much less common than it was. However, it remains a dire threat to patients whose immune systems are suppressed (including transplant recipients and AIDS and cancer victims) and to those who are critically ill or injured. Pneumocystis pneumonia is a leading cause of death in AIDS. A vaccine against bacterial pneumonia is recommended for people over 65 and other high-risk groups.