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The Link Between Cooling Towers and Legionnaires’ Disease

Posted in Legionella,Legionnaire's disease,Our Blog,Outbreaks & Recalls on May 28, 2019

Lately there have been a lot of reports of Legionnaires’ disease in the news.  New York has been the recent front-page outbreak, but it has become an increasing problem in the United States.  As recent as 2015 (less than 5 years) Legionnaires’ disease has claimed 12 lives in New York and sickened another 120 people and counting. This leaves a lot of questions, like what’s the deal with Cooling Towers and Legionnaires’ Disease?

If you haven’t heard of this disease, you may not be alone.  It is relatively new to the surveillance scene, so there haven’t been too many reports until recent years.  Is it because it wasn’t around before?  Unlikely.  The Legionella bacterium has been around for ages.  An increase in testing is likely the reason for the recent uptick in statistics.  The disease presents symptoms similar to common pneumonia infection and may even look the same on a chest x-ray.  If not specifically diagnosed, the pneumonia illness will be treated like typical pneumonia, but without proper antibiotic treatment, illness will persist longer with worsened symptoms.

What is Legionnaires’ Disease?

Symptoms of Legionnaires’ disease include cough, shortness of breath, fever, muscle aches, and headaches.  Additional symptoms include diarrhea, nausea, and confusion.  Symptoms often appear within 2 to 10 days after exposure, but it could take up to 2 weeks for some to experience these symptoms.

Most victims will require hospitalization.  A staggering 1 in 10 people infected will die.  There is no vaccine for Legionnaires’ disease at this time.

Legionnaires’ is often associated with cooling towers and hot tubs as these are areas where the bacteria can grow and thrive.  These infection hubs also aerosolize water, allowing the bacteria to make its way into the unknowing host quite easy.

The more recent outbreaks have been linked to cooling towers.  But why cooling towers?  How does that work?

Why Cooling Towers?

Let’s start by figuring out what a cooling tower is and does.  Do you remember learning about thermodynamics in school?  Chances are unless you are in engineering or some other science degree you might have skimmed over the topic.

Thermodynamics is a simple concept of heat transfer in its basic sense.  Hot things don’t want to be hot.  Heat will move from a hotter place to a cooler place.  For those that live in the South, we know that all too well.  But, Summer insulation woes aside, a cooling tower is used to remove heat from a building or facility.

Water is literally sprayed down a tower.  Air comes in from the sides of the tower and passes through the falling water.  While this happens, a heat exchange occurs.  The heat and evaporated water evaporates out of the top and the cooled water collects at the bottom of the tower and used in air-conditioning systems.  The cycle continues over and over with the used warmed water pumped back into the tower, heat transfer, then cold water at the bottom.  Rise, wash, repeat.

Cooling towers have many industrial uses, but the ones that are hot topics for Legionnaires’ disease are heating, ventilation, and air conditioning (HVAC) applications.

The Link Between Legionnaires’ Disease and Cooling Towers

If not properly maintained and disinfected, the large amounts of water found in cooling towers are potential breeding grounds for Legionella bacteria.  Legionella bacteria are “heat loving bacteria,” making the warm temperatures found in cooling towers an ideal home.  The nutrients, sediment, heterotrophic biofilm, and amoebae contribute to the perfect environment for these bacteria.

A few years ago, scientists from the Center for Disease Control and Prevention’s (CDC) Pneumonia Response and Surveillance Laboratory with funding from the CDC Office of Advance Molecular Detection conducted a study using surveillance samples of 196 cooling towers to “determine the distribution of Legionella in a subset of regionally diverse US CT’s [cooling towers] and characterize the associated microbial communities.”

These samples were taken between July 2016 and September 2016 across 8 of the 9 continental US climate regions.  These samples were screen and grown on cultures to further characterize the bacteria.  The scientists found that 84% (164 samples out of 196 taken) were positive for the harmful bacteria.  Samples from all climate regions were positive.  That is a significant rate of occurrence!

If building managers and companies know that there is a risk for Legionella bacteria, you would think that they would do something to help prevent it.  In fact, not doing something to prevent it could make the company vulnerable to damages from those who become infected with this serious illness as a result of neglect.

So, what can building managers and companies do?

Prevention Measures to Reduce the Growth of Legionella Bacteria

Legionella is a bacteria.  Bacteria require specific conditions to thrive.  While the nature of cooling towers gives them an ideal environment, there are preventative measures that companies can take to reduce the risk.

Choose a Healthy Water Source

Companies may choose to use municipal or well water from a holding tank as a water source.  This can contain impurities such as sediment, sludge, and rust.  In some cases, surface water may be used sourced from lakes, rivers, or reservoirs.  These are more dangerous sources, as they could be naturally laced with nutrients and microorganisms naturally found in the environment.

Disinfecting the cooling tower and any holding tank used to house the water twice a year is a start.  If sourcing environmental water, it should be first treated with an antimicrobial before it is introduced to the cooling tower.

Regular Disinfection Protocol

Cooling towers are not a closed system.  They are open to the environment.  As a result, bacteria that are killed with a disinfection process will quickly recolonize.  To help reduce this recolonization, changing up the chemicals is necessary.  Alternating between two non-oxidizing biocides or alternating between an oxidizing antimicrobial with a non-oxidizing antimicrobial may help.

Manage Biofilms

Dirt, dust, and other particles that fall into the cooling tower from the outside environment contribute to the biofilms that can form in the fooling tower.  These biofilms are essential for Legionella bacteria as it provides the needed nutrients for the bacteria to grow and thrive.  Appropriate detergents and cleaning maintenance are important to minimize the risk of Legionella growth.

Early Diagnosis is Key to Survival

If you begin experiencing symptoms similar to pneumonia or Legionnaires’ disease and have stayed in a hotel or been in a hot tub recently, let your doctor know.  Proper diagnosis can be the difference between life and death.  Without this key information, your doctor may not think to order a simple test that will provide a better treatment plan, otherwise you may receive generic pneumonia treatment.

Stay tuned to MakeFoodSafe.com for information on Legionnaires’ disease outbreaks and other news.

By: Heather Van Tassell, Contributing Writer (Non-Lawyer)