Defending against Legionella

Sept. 28, 2015

As Legionnaires’ disease outbreaks grow, the water industry must take steps to protect human health.

In the October issue of Water Technology, Technical Editor Dr. Joseph Cotruvo outlined why the need for the U.S. Environmental Protection Agency (EPA) to develop guidelines that encourage supplemental disinfection, especially in the wake of an increased number of Legionnaires’ disease outbreaks.

According to the Centers for Disease Control’s (CDC) Morbidity and Mortality Weekly Report (MMWR) covering the years 2011-2012, waterborne disease outbreaks numbered 431 cases of 10 microbial diseases and 102 hospitalizations. Legionella was responsible for 21 outbreaks and 111 cases. It was the only cause of any of the deaths.

Legionella is often found in small systems, and Cotruvo notes many legionellosis cases occur in hospitals, long-term care facilities, hotels and apartment buildings. The MMWR reported that 12 deaths occurred in hospitals/health care and long-term facilities, while two deaths occurred in the hotels category and one happened in the apartment category.

The sources of the outbreaks highlighted in the MMWR were sometimes unknown, but others were traced back to ornamental fountains, a cooling tower and a storage tank, writes Cotruvo. A recent outbreak in New York City was traced back to cooling towers. Ice machines are another potential contamination point. Outbreaks were also reported at San Quentin State Prison, a veterans home in Quincy, Illinois, and others occurred internationally. Some cases in the U.S. and around the world are likely underreported.

Cotruvo shares that current regulations hinder supplemental disinfection efforts in drinking water systems. Treatment options exist to remove Legionella and viruses, but reseeding could occur in the following situations:

  • If a few microorganisms survive water treatment
  • From soil contamination in water line leaks and breaks
  • During plumbing repairs
  • New construction in which the plumbing system has not been properly disinfected prior to commissioning and the facility’s placement into service

The EPA’s Safe Drinking Water Act was issued more than 30 years ago when regrowth issue were not under consideration, explains Cotruvo. The CDC recommends aggressive monitoring following outbreaks. While the connection between water and biofilm Legionella is not well-understood, regular monitoring and maintenance may reduce risks.

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