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.

Pneumococci organism
Lungs
Pneumonia
White nail syndrome
Pneumococcal pneumonia
Respiratory system

Alternative Names

Causes, incidence, and risk factors

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

Symptoms

The main symptoms of pneumonia are:

• Cough with greenish or yellow mucus; bloody sputum happens on occasion
• Fever with shaking chills
• Sharp or stabbing chest pain worsened by deep breathing or coughing
• Rapid, shallow breathing 
• Shortness of breath

• Headache
• Excessive sweating and clammy skin
• Loss of appetite
• Excessive fatigue 
• Confusion  in older people

Signs and tests

If you have pneumonia, you may be working hard to breathe, or may be breathing fast. Crackles are heard when listening to your chest with a stethoscope. Other abnormal breathing sounds may also be heard through the stethoscope or via percussion (tapping on your chest wall).

The following tests may show signs of pneumonia:

• Chest x-ray
• Gram's stain and culture of your sputum to look for the organism causing your symptoms
• CBC to check white blood cell count; if high, this suggests bacterial infection
• Arterial blood gases to check how well you are oxygenating your blood
• CAT scan of the chest
• Pleural fluid culture if there is fluid in the space surrounding the lungs

Expectations (prognosis)

With treatment, most patients will improve within two weeks. Elderly or debilitated patients who fail to respond to treatment may die from respiratory failure.

Complications

Empyema or lung abscesses are infrequent, but serious, complications of pneumonia. They occur when pockets of pus form around or inside the lung. These may sometimes require surgical drainage.

Calling your health care provider

Call your doctor if:

• You have worsening respiratory symptoms.
• You have shortness of breath, shaking chills, or persistent fevers.
• Your breathing is rapid or painful.
• You cough up bloody or rust-colored mucus.
• You have chest pain that worsens when you cough or inhale.
• You have night sweats or unexplained weight loss.
• You have a weak immune system, as with HIV or chemotherapy.

Infants with pneumonia may not have a cough. Call your doctor if your infant makes grunting noises or the area below the rib cage is retracting while breathing.

Prevention

• Wash your hands frequently, especially after blowing your nose, going to the bathroom, diapering, and before eating or preparing foods.
• Don't smoke. Tobacco damages your lung's ability to ward off infection.
• Wear a mask when cleaning dusty or moldy areas

Vaccines can help prevent pneumonia in children, the elderly, and people with diabetes, asthma, emphysema, HIV, cancer, or other chronic conditions:

• Pneumococcal vaccine (Pneumovax, Prevnar) prevents Streptococcus pneumoniae.
• Flu vaccine prevents pneumonia and other infections caused by influenza viruses. It must be given yearly to protect against new viral strains.
• Hib vaccine prevents pneumonia in children from Haemophilus influenzae type b.

Taking deep breaths may help prevent pneumonia if you are in the hospital -- for example, while recovering from surgery. Often, a breathing device will be given to you to assist in deep breathing.

If you have cancer or HIV, you should talk to your doctor about additional ways to prevent 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.

---

Review Date:10/31/2005
Reviewed By: Frederic F. Little, M.D., Department of Allergy and Pulmonary/Critical Care Medicine, Boston University School of Medicine, Boston, MA. Review provided by VeriMed Healthcare Network.