How is Legionnaires disease?

Updated: Mar 11, 2021
  • Author: Chinelo N Animalu, MD, MPH; Chief Editor: Michael Stuart Bronze, MD  more...
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Legionellae should be sought in hospitalized patients with an increased risk for infection and subsequent death. If 1 definite case or 2 possible cases of nosocomial LD occur among in patients, initiate an investigation for a hospital source.

Legionellae transmission can also be discouraged through the routine maintenance of cooling towers and the use of only sterile water for filling and rinsing nebulization devices. Improved design and maintenance of cooling towers and plumbing systems can also help.


Superheating water to 70-80°C, with flushing of distal sites, may help to prevent water contamination.

Copper-silver ionization units—which produce metallic ions that disrupt the bacterial cell wall, thus resulting in lysis and cell death—are very effective at eradicating legionellae; they provide sustained protection.

Ultraviolet light kills legionellae by damaging cellular deoxyribonucleic acid (DNA). This modality is effective when disinfecting localized areas, but because it provides no sustained protection, adjunctive treatments must be used.

Hyperchlorination of water is no longer recommended, because legionellae are fairly chlorine resistant, and chlorine decomposes at the higher temperatures found in the hot water systems it is used to treat.

Following reports of LD in newborns who were infected during water births, [5] the Arizona Department of Health Services issues recommendation for minimizing the risk of Legionella contamination in tubs used during the water birthing process, such as flushing out stagnant water and sediment from hoses by running hot water through it for 3 minutes before using it to fill the tub. [19]

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