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When you think about water safety, Legionella probably isn't the first thing that comes to mind. Yet, this sneaky bacterium is more common—and more dangerous—than many realize. Let's dive into what Legionella is and why it's a bigger and more complex problem than you might think.
Legionella is a type of bacteria that naturally lives in freshwater environments like lakes and streams. Normally, these bacteria don't pose much of a threat. But when they find their way into artificial water systems, such as cooling towers, hot tubs, and plumbing systems, they can multiply and spread, causing serious health issues.
The bacteria can cause Legionnaires' disease, a severe form of pneumonia, and Pontiac fever, a milder flu-like illness. Legionnaires' disease can be particularly deadly, especially for the elderly, smokers, and people with weakened immune systems. The fatality rate is about 10% for otherwise healthy people, but reaches a staggering 25% for people with underlying conditions.
A common misconception is that consuming water with Legionella is what makes you sick. Rather, it’s the inhalation of contaminated water droplets that actually causes Legionnaire’s disease or Pontiac fever. People usually contract these illnesses from showers or hot tubs, when warm, vaporized water droplets containing Legionella are inhaled.
Legionella is a naturally occurring bacteria in freshwater sources. In these habitats, Legionella exist in low numbers and don’t pose any health risks. The real threat happens when the bacteria start to multiply to high numbers. But what would cause that to happen?
Artificial, man-made water systems often create the perfect conditions for Legionella to rapidly multiply: warm temperatures, stagnant water, and the right nutrients. This means that cooling towers, hot tubs, and decorative fountains often create the perfect environment for Legionella to thrive.
In 2018, the CDC reported approximately 10,000 cases of Legionnaire’s disease. But experts believe the actual number is much higher - possibly up to three times more -because the disease is so frequently underdiagnosed and underreported. It's easily mistaken for other forms of pneumonia, meaning that many cases go undiagnosed. Furthermore, the CDC reports that cases of Legionnaire’s disease have been increasing at a average rate of 9% per year, pointing to a dangerous trend in disease prevalence. Since 2000, the number of cases in the US has increased 10X, with a sharp upward trend since 2016. The reasons for this sharp increase are not clear, but there are a number of possible factors.
One strong contender is aging plumbing systems. Legionella are known to multiply at high rates within biofilms. Biofilms are sticky layers of mucus produced by bacteria when they accumulate on moist surfaces. Aging pipes are especially prone to biofilm formation, leaving them susceptible to Legionella growth and creating a major health risk. Water infrastructure throughout the US is aged and in need of replacement in many regions, increasing the risk of Legionnaire’s disease over time.
In the summer of 2015, the Bronx, New York, experienced one of the most significant outbreaks of Legionnaires' disease in recent history. The outbreak resulted in 138 reported cases and 16 deaths. Officials were initially puzzled as there were no common buildings visited by all these patients, and the people affected resided across a fairly large area. Officials then began investigating outdoor exposure from cooling towers as a possible source. The Opera House Hotel cooling tower was eventually identified as the source of this outbreak – these towers emanate warm mist which can spread Legionella, and the hotel’s cooling tower had not been properly maintained. This tragic event highlighted the severe consequences of neglecting water system maintenance and spurred immediate regulatory actions.
Following the outbreak, New York City implemented stringent regulations to prevent future incidents. The new rules required the registration, regular inspection, and maintenance of cooling towers. Building owners must now adhere to a rigorous schedule of cleaning and disinfecting, and they are mandated to report any Legionella test results to the city. These measures aim to significantly reduce the risk of Legionella proliferation in large building water systems and protect public health. New York City was the first city in the United States to implement legislation specific to the prevention of Legionella in building water systems.
Legionella might not be on everyone's radar, but it should be. The bacteria's ability to thrive in water systems common in large buildings makes it a hidden threat to public health. By understanding the risks and implementing strong preventative measures, we can keep our water systems safe and protect the people who rely on them.
