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Legionella – Why is this suddenly as common as avocado toast?

It seems like every day we hear a new story about a Legionella outbreak – whether it is an offshoot of the Flint, Michigan lead crisis or the more recent 140 plus confirmed cases linked to the NC State Fair in October 2019. We know there is no shortage of other news in the world, so why are we hearing so much about this now? Let’s take a closer look.

Legionnaires’ disease got its name after an outbreak of pneumonia among attendees of an American Legion convention in Philadelphia in 1976. Years later, the bacterium that caused this illness was discovered and named “Legionella pneumophila.” This bacterium also causes Pontiac fever, a milder illness than Legionnaires’ that resembles the flu. Both Legionnaires’ disease and Pontiac fever, jointly referred to a legionellosis, are reported to local health departments for investigation.

Since 2000, the number of legionellosis cases has continued to rise annually. Health departments reported nearly 7,500 cases throughout the US in 2017. Just last week, on November 6, 2019, the CDC reported 9,933 cases of legionellosis, with Legionnaires’ disease making up the vast majority of those cases. That is more than an eight-fold increase since the numbers began to climb nearly two decades ago.

The National Academies of Sciences, Engineering, and Medicine estimates that as many as 70,000 people may suffer from the disease each year, according to a report released in August.

Why is this?

Many experts believe a number of factors are responsible for the increase including old and failing infrastructures; an aging population; an increase in awareness and testing for the disease; water conservation efforts and even climate change. But are there other reasons? Are we missing the real problem?

But there are other reasons, and they may not be as obvious…

Legionella bacterium is found throughout the world, primarily in water and moist environments (e.g., lakes, rivers, ground water and soil). People get Legionnaires’ disease or Pontiac fever by breathing in small droplets of water in the air that contain Legionella or by aspirating on drinking water that is contaminated with Legionella. Legionellosis outbreaks have been associated with buildings or structures that have complex water systems, such as hotels and resorts, long-term care facilities, hospitals, and cruise ships. Implicated sources of infection include water used for showering, hot tubs, decorative fountains, and even cooling towers (structures that contain water and a fan as part of centralized air-cooling systems). Many regulations and guidelines have been developed, some not informed by science, in hopes of helping buildings and facilities to decrease the incidence of legionellosis.

So, if there are more regulations, why are we not seeing a decrease in incidence?

The commitment to fighting this problem is an expensive undertaking. According to an article from Medicalxpress, in 2012, the yearly cost of treating Legionnaires’ disease, based on hospitalization claims, was $434 million (likely much higher today). Add to that the cost of remediation if Legionella bacterium is found– flushing out the water systems or complete replacement to get rid of the bacteria. This year, California alone has spent $8.5 million cleaning up an outbreak that resulted in the death of one inmate at a Stockton prison.

Finding Legionella bacterium can be catastrophic. Disruption of business, negative media coverage, lawsuits and potential financial ruin are all real possibilities. That kind of fear can lead building managers to avoid testing or actively looking for Legionella, said Laura Ehlers, who directed the recent study for the National Academies.

In addition, even facilities that have water management plans in place are still finding Legionella showing up on water testing setting into motion a cycle of treating and testing. Even with a good water management plan, Legionella risk is ever present, according to Jonathan Garoutte, administrator of the Missouri health department’s section for environmental public health. “Legionella finds places within large complex water systems to hide,” he said.

Ehlers also identified an unusual source: the green building movement. She said LEED-certified buildings and other efforts to conserve water often hold that water at temperatures that are unsafe and have “made a growth dish for Legionella.”

All regulatory agencies agree that a testing requirement would be very expensive for smaller facilities and would divert attention from analyzing the safety of the system as a whole. A key question for facilities is how to proactively guard against the bacteria so that if Legionella is found with testing, they will not end up footing millions of dollars in bills.

With this knowledge, we must now ask ourselves whether our focus on testing and the development of regulations for expensive water treatment programs is having unintended effects. Are we focusing on meeting ineffective regulations or are we instead analyzing the body of science and knowledge about this potentially deadly disease and using it to develop common sense guidelines to control the eventual growth of this bacteria? Legionella may still be everywhere, but let’s use science-based methodologies to render it no more worrisome than an overabundance of avocado toast.

For more information about Legionella and how to reduce risk, contact the experts at Cogency at

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