The spread of legionella these days is quite alarming as people are falling victim to it on a daily basis. Legionellosis is a collective term for diseases caused by legionella bacteria including the most serious Legionnaires’ disease, as well as the similar but less serious conditions of Pontiac fever and Lochgoilhead fever.


What is Legionnaires’ disease and who does it affect?

Caused due to legionella, this condition is actually a fatal form of pneumonia and everyone is susceptible to infection. The risk of contracting this disease goes up with age, but there are specific groups it affects such as those over 45 years of age, people suffering from chronic respiratory or kidney disease, smokers and heavy drinkers, anyone with an impaired immune system, and individuals with diabetes, lung and heart disease. Symptoms of this disease include high temperature, feverishness and chills, muscle pains, headaches, cough, diarrhea and signs of mental confusion, etc.


Where does it come from?

The bacterium legionella pneumophila and related bacteria are common in natural water sources such as rivers, lakes and reservoirs, but usually in low numbers. They may also be found in purpose-built water systems such as cooling towers, evaporative condensers, hot and cold water systems and spa pools in all kinds of premises. However, the conditions are rarely right for people to catch the disease from these sources.


How do people get it?

When people are exposed to the bacteria growing in purpose-built systems where water is maintained at a temperature high enough to encourage growth, it is likely that outbreaks of the illness will occur. The disease is contracted when they inhale small droplets of water suspended in the air, which contain the bacteria. They can also succumb if contaminated water goes into the lungs while drinking. At times, certain situations enhance the risk from legionella – take a look:

  • Water is stored and re-circulated.
  • As mentioned, it is quite possible for breathable water droplets to be generated and dispersed. For instance, aerosol is created by cooling towers or water outlets.
  • Deposits like rust, sludge, scale, organic matter and biofilms are present for boosting bacterial growth. They provide a source of nutrients for the organism to thrive.
  • Water temperature the water temperature in all or some parts of the system may be between 20-45 °C, which is ideal for growth.

How to prevent Legionella growth

If conditions are favorable, the bacteria may grow increasing the risks of Legionnaires’ disease and it is therefore important to control the threats by introducing appropriate measures. Here goes:


The disinfectant amounts have to be correct

If the disinfectant levels (chlorine, mono-chloramine, chlorine dioxide, ultraviolet light, and ozone) in the water systems of your building are less than what they should be, there are high chances of legionella growing in the water. In some buildings, processes such as heating, storing, and filtering can reduce the amount of available disinfectant, allowing legionella to grow if steps are not taken to stop it. If required, please arrange for long-term supplemental disinfectants to be added to the water to up the levels of disinfectant, which in turn stops the legionella from spreading.


The water temperature has to be right

Legionella grows best within a certain temperature range (77°F-108°F). To keep water outside the range for legionella growth, it is necessary to maintain an optimum temperature. Hot water should be kept warm, while cold water needs to be chilly.  In warm climates, water in pipes that carry cold water may reach a temperature that allows Legionella to grow. When it comes to hot water, the water heaters should be maintained at correct temperature while following local and state anti-scald regulations. At times, maximum temperatures allowed by your state may be too low to limit legionella growth. Engineering controls that mix hot and cold water together at or near the point of use can reduce the risk of scalding while allowing water in pipes to remain hot enough to limit legionella growth.


Stop stagnation

When the smooth flow of water is affected due to some reason, it causes stagnation in some areas. Biofilm growth occurs, which leads to water temperatures dropping to levels for allowing legionella to grow and decrease levels of disinfectant as well. Understand the flow of water in your building so the risky areas where water might become stagnant, can be identified better.


Operate and maintain equipment

Maintaining and operating your building’s equipment effectively will help prevent biofilm, organic debris, and corrosion from contaminating your water system; all of these provide a habitat and nutrients for legionella.


Keep tabs on external aspects

It is crucial to keep an eye on external factors that can impact the water entering a building that encourages legionella in complex water systems. Construction, water main breaks, etc. are important factors to take into account.

Seek professional help so you can conduct a regular risk assessment for legionella in the building you reside.