Pneumonia

Definition

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

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

Pneumonia can range from mild to severe, even fatal. The severity depends on the type of organism causing pneumonia as well as your age and underlying health.

Alternative Names

Causes

Bacterial pneumonias tend to be the most serious and, in adults, the most common cause, especially 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