In 1976, convention attendants at the American Legion in Philadelphia came down with a lung infection that was assumed to be pneumonia. However, once it was discovered this disease was different, it was named Legionnaires’ disease after the American Legion.



Legionnaires’ disease is caused by a type of bacteria called Legionella, which are found naturally in water-based environments. The Legionellosis infection develops in two distinct forms: Legionnaire’s disease, resulting in pneumonia-like symptoms, and Pontiac Fever, which is a milder version of the infection.


Exposure and Risk Factors

Transmission of the disease occurs by breathing in aerosolized water containing bacteria, found in showers, whirlpools, cooling towers and hot water systems.

  • You can become infected by breathing in infected water vapors.
  • Outbreaks occur when multiple people breathe in the same contaminated vapors (however, it is not contagious from person to person).
  • Adults ages 65 and older are more at risk because of their weakened immune systems, as well as smokers and chronic lung disease sufferers.



Signs of Legionnaires’ disease usually become evident 2-14 days after being exposed to the bacteria.

  • Symptoms include high fever, chills, cough, muscle aches and headaches
  • X-rays and blood work are needed to detect evidence of the bacteria.
  • Pontiac Fever includes many of the symptoms of Legionnaires’ disease; however, usually they disappear on their own without treatment.


Since Legionnaires’ disease mirrors the symptoms of pneumonia, many sufferers go undiagnosed each year. Most cases are found in the summer and early fall, but the disease can happen any time of year. The disease can be very serious and cause death in 5-30 percent of cases, but most people can be successfully treated with antibiotics.



  • Because the disease is caused by naturally occurring bacteria, the most you can do to prevent its transmission is to keep Legionella out of the water supply.
  • If you use or own a whirlpool tub, ensure it has been properly disinfected before use.
  • Use respirators or masks if you work with commercial air conditioning or water treatment systems.
  • Stop smoking! The healthier you are, the easier it will be for your immune system to battle disease.


Content: Zywave, Inc.