Pneumonia

Definition

Pneumonia is an infection of the lungs. Many different organisms can cause it, including bacteria, viruses, and fungi.

Alternative Names

Bronchopneumonia; Community-acquired pneumonia

Causes

Pneumonia is a common illness that affects millions of people each year in the United States.

Bacterial pneumonias tend to be the most serious and, in adults, the most common cause of pneumonia. The most common pneumonia-causing bacterium in adults is Streptococcus pneumoniae (pneumococcus).

Respiratory viruses are the most common causes of pneumonia in young children, peaking between the ages of 2 and 3. By school age, the bacterium Mycoplasma pneumoniae becomes more common.

In some people, particularly the elderly and those who are debilitated, bacterial pneumonia may follow influenza or even a common cold.

Many people contract pneumonia while staying in a hospital for other conditions. This tends to be more serious because the patient's immune system is often impaired due to the condition that initially required treatment. In addition, there is a greater possibility of infection with bacteria that are resistant to antibiotics.

See also:

• Aspiration pneumonia
• Atypical pneumonia
• CMV pneumonia
• Hospital-acquired pneumonia
• Legionella pneumonia
• Pneumocystis carinii pneumonia
• Pneumonia in immunocompromised host
• Viral pneumonia
• Walking pneumonia

References

Marx JA, Hockberger RS, Walls RM, eds. Rosen’s Emergency Medicine: Concepts and Clinical Practice. 5th ed. St. Louis, Mo: Mosby; 2002;

Cohen J, Powderly WG. Infectious Diseases. 2nd ed. New York, NY: Elsevier, 2004.

Mandell, GL, Bennett JE, Dolin R, eds. Principles of Infectious Diseases. 5th ed. New York, NY: Churchill Livingstone, 2000.

Mandell LA, Wunderink RG, Anzueto A, et al. Infectious Diseases Society of America/American Thoracic Society consensus guidelines on the management of community-acquired pneumonia in adults. Clin Infect Dis. 2007 Mar 1;44 Suppl 2:S27-72.

American Thoracic Society. Guidelines for the management of adults with hospital-acquired, ventilator-associated, and healthcare-associated pneumonia. Am J Respir Crit Care Med. 2005 Feb 15;171(4):388-416.