Distributed Energy

The Threat of Legionnaire’s Disease

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In 1976 a pneumonia outbreak sickened 221 people and killed 34. The cause was a mystery that puzzled scientists for months. It was eventually traced to a bacterium that researchers named Legionella pneumophila because many of the affected individuals were members of the American Legion, exposed at a convention.

Legionella is typically found in freshwater environments. It thrives at temperatures of 95 and 115 degrees F, and between 5.0 and 8.5 pH. The bacterium becomes a problem when it colonizes in warm water, like that found and HVAC systems, cooling towers, water distribution pipes, and fountains.

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As temperatures rise and air conditioning systems crank into high gear this summer, facility managers are wise to consider the sanitation of their systems and the quality of the air they’re circulating.

Legionellosis, or legionella infection, is caused by the inhalation of water aerosols containing the bacteria. The CDC reports that 5,000 cases of Legionnaires’ disease are reported annually in the United States, but it also estimates that more than 90 percent of cases go unreported. People with compromised immune systems and respiratory illnesses are much more likely to become infected.

According to the Building Owners and Managers Association (BOMA), “Of the recent cases investigated by CDC, the most common source of building-associated Legionnaires’ disease outbreaks was drinkable water (56 percent), such as water used for showering, followed by cooling towers (22 percent) and hot tubs (seven percent).”

In 2015 the American Society of Heating Refrigeration Air Conditioning Engineers (ASHRAE) issued the first industry standard to address Legionnaires’ disease prevention, Standard 188-2015, Legionellosis: Risk Management for Building Water Systems.  The document offers risk management guidelines developed by industry experts and serves as a valuable resource for building owners and managers.

Some of the standard’s best practices include prevention plans for corrosion, scale, and deposits in water and cooling systems, in addition to annual washout and disinfection programs. The CDC also offers an informative toolkit to help building owners and facility personnel interpret the standards and further reduce their system’s risk of cultivating bacteria.

What steps does your organization take to prevent legionellosis? What strategies have you found most useful? BE_bug_web

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  1. Laura————very interesting article. This bug (Legionella) along with Serratia are fond of growing in water systems. Both are serious pathogens and are becoming increasingly resistant to antibiotics. Nonetheless, the State of California not only allows the use of recycled water to be used for cooling towers and irrigation of hospital landscape, but actively promotes its use. The State also refuses to consider the transfer of antibiotic resistant genes, a serious public health issue with recycled water. Thus there is what’s known as a “legal fiction” here as the water can be legal but on examination hardly safe. Thus there is a schism here: what is safe versus what is legal, including what is profitable and what is politically acceptable. When you rely on your politician, even the best money can buy, for medical advice, I think you are in trouble.

    Dr Edo McGowan

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