Legionellosis or Legionaires' Disease
in Your Home

Legionellosis is a serious and sometimes fatal form of pneumonia caused by the Legionella bacterium species found naturally in the environment thriving in warm water and warm damp places.

They are commonly found in lakes, rivers, creeks, hot springs, soil and potting mix. The bacteria was first identified in 1977, as the cause of an outbreak of severe pneumonia in a convention center in which 34 people died in the U.S. in 1976 but the organism has been around for decades with cases as far back as 1947 confirmed.

The CDC (Center for Disease Control) estimates 8,000 to 18,000 people get Legionaires' disease each year with estimates of 5% to 30% of these resulting in related deaths.

The bacterial organisms can be spread by aerosols such as wind and infection results from inhalation of the contaminated water sprays or mist-producing devices like air conditioning systems, water heaters, whirlpools, showers, room humidifiers, decorative water fountains, and spas. The bacteria are not spread from one person to another.


Legionellosis has two forms:

  • Pontiac fever: a mild respiratory infection requiring no treatment (may even go undiagnosed).
  • Legionnaires' disease: a serious and potentially fatal form of pneumonia treatable with antibiotics.

Persons with Pontiac fever have fever and muscle aches but do not have the pneumonia. They usually get better in 2 to 5 days without treatment.

Persons with Legionaires' disease are generally much sicker. They usually have fever (from 102F - 105F), chills, and a cough, which might produce sputum. Some people also have muscle aches, headache, tiredness, loss of appetite, and occasionally diarrhea making the disease hard to diagnose from other types of pneumonia or flu symptoms.


Possible sources of Legionellosis include:

  • Cooling towers
  • whirlpool spas
  • Domestic water system - shower heads and aerators
  • Decorative fountains and misters
  • HVAC, humidifiers, and HVAC ductwork
  • Nebulizers and other respiratory-care equipment
  • warm stagnant water

Control methods include:

  • Using sterile water for rinsing nebulization devices and other respiratory-care equipment
  • Do not use large-volume room-air humidifiers that create aerosols unless they can be sterilized and disinfected daily.
  • Keep HVAC drip pans cleaned and dry making sure they drain adequately
  • Ensure that water from condensation and other sources does accumulate in HVAC ductwork
  • Ensure decorative fountains are cleaned on a routine basis
  • Ensure plant misters and other forms of misters are routinely cleaned
  • Replace heavily scaled faucets and shower heads
  • Avoid faucet aerators
  • Choose copper pipe over other materials. Copper resists Legionella colonization. Steel is second best. Plastics are the worst.
  • Maintain an adequate level of a biocide such as chlorine in a spa or pool

Anyone can get legionellosis, but the illness most often strikes middle-aged and older persons, especially those who smoke cigarettes or have chronic lung disease. Persons whose immune systems are weakened by cancer, kidney failure requiring dialysis, diabetes, or HIV infection are also at high risks.

Elimination of the bacterial breading ground will minimize the risk.

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