Pneumonia Types Legionnaires

In 1976, an outbreak of pneumonia at an American Legion convention in Philadelphia led to the identification of a new type of pneumonia called Legionnaire’s disease. According to the Centers for Disease Control and Prevention, Legionnaire’s disease hospitalizes 8,000 to 18,000 Americans every year. Although healthy people usually recover, Legionnaire’s disease is fatal in 5 to 30 percent of cases, making it one of the deadliest types of pneumonia.

Legionnaire’s Disease Causes

Legionnaire’s disease is caused by a bacterium called Legionella. Legionella is present in the environment, and thrives in damp, warm areas. Legionnaire’s disease causes include contamination of water systems, including:

  • Air conditioning systems
  • Fountains
  • Swimming pools
  • Water misters
  • Whirlpool spas.

Once Legionella enters a water system, it becomes airborne in contaminated water droplets. The majority of Legionnaire’s disease cases occur when people breathe in infected water droplets. Large, complex water systems seem more susceptible to Legionnaire’s disease than smaller systems, so most outbreaks occur in larger buildings or on cruise ships.

In addition, some people catch Legionnaire’s disease by drinking contaminated water and accidently getting some of the liquid into the lungs (a condition known as aspiration). A small number of infections result from working with contaminated soil. Legionella can also cause a mild illness called Pontiac disease, which doesn’t progress into any types of pneumonia.

Legionnaire’s Disease Risk Factors

Legionnaire’s disease causes pneumonia, but not everyone exposed to the bacteria develops pneumonia. Risk factors for Legionnaire’s disease include:

  • Age 65 or older
  • Cancer
  • Chronic lung disease
  • Diabetes
  • Kidney disease
  • Smoking
  • Weakened or compromised immune systems.

People who maintain air conditioning cooling towers also have a higher than normal risk of Legionnaire’s disease.

Legionnaire’s Disease Symptoms

Legionnaire’s disease symptoms begin within two to 14 days after exposure to the Legionella bacteria. Legionnaire’s disease causes:

  • Chest pain
  • Chills and a fever of 104 degrees Fahrenheit or higher
  • Confusion
  • Coughing, possibly with mucus or blood
  • Diarrhea
  • Dyspnea (shortness of breath)
  • Fatigue
  • Headaches
  • Loss of appetite
  • Muscle aches and pain
  • Nausea and vomiting.

Complications of Legionnaire’s Disease

While Legionnaire’s disease causes pneumonia, the bacteria can also infect wounds and internal organs other than the lungs. In addition, Legionnaire’s disease can cause life-threatening complications such as:

  • Acute kidney failure
  • Respiratory failure
  • Septic shock.

Legionnaire’s Disease Treatment

Legionnaire’s treatment includes introducing antibiotics as soon as possible. Generally speaking, the sooner Legionnaire’s disease treatment begins, the better the outcome.

Legionnaire’s Disease Prevention

Legionnaire’s disease prevention is primarily based on maintaining clean water systems. Individuals can also lower their risk of Legionnaire’s disease — and other types of pneumonia — by not smoking.


Centers for Disease Control and Prevention Staff. (2008). Patient facts: Learn more about Legionnaire’s disease. Retrieved March 8, 2010, from the Centers for Disease Control and Prevention Web site:

Mayo Clinic Staff. (2008). Legionnaire’s disease. Retrieved March 8, 2010, from the Mayo Clinic Web site:

Occupational Safety and Health Administration Staff. (2008). Legionnaire’s disease. Retrieved March 8, 2010, from the Occupational Safety and Health Administration Web site: