Pneumonia is particularly serious in people with impaired immune systems, particularly AIDS patients, in whom pneumonia causes about half of all deaths. The disease is also very dangerous in people with cirrhosis, sickle cell anemia, multiple myeloma, and in those who have had their spleens removed. Legionella is particularly virulent and can cause damage throughout the body. They are frequently a result of aspiration pneumonia, when a mixture of organisms is carried into the lung. Abscesses can cause hemorrhage in the lung if untreated, but antibiotics that target specific anaerobic bacteria and other organisms have significantly reduced their danger.
Viral pneumonia is usually very mild but there are exceptions.
Influenza pneumonia can be very serious. Complications of Pneumonia Bacteremia. Bacteremia is also a frequent complication of other gram-negative organisms, including Haemophilus influenzae. Pleural Effusions and Empyema. The narrow zone between these two pleural membranes normally contains a tiny amount of fluid that helps lubricate the lung.