Legionella in water - what is worth knowing?

Although we don't usually consider what lurks in water systems, there are microorganisms that can thrive there - silently and without any obvious warning signs. One of these is the Legionella bacteria, responsible for serious respiratory infections. This topic is particularly common in public buildings, hotels, and hospitals, but it also applies to private homes.

What is Legionella and where does it occur?

Legionella is a type of bacteria naturally found in aquatic environments - lakes, rivers, and soil. Problems arise when the bacteria enter artificial water systems, such as hot water systems, showers, air conditioning systems, or jacuzzis. Under favorable conditions, it can multiply rapidly there.

The best conditions for Legionella to thrive are:

• water temperature between 25–45°C,
• water stagnation (e.g., in infrequently used systems),
• the presence of biofilm and sediment,
• and lack of adequate disinfection.

Importantly, the mere presence of bacteria in water isn't the biggest threat. Infection most often occurs through inhaling water aerosols-tiny droplets suspended in the air, for example, while showering.

Legionellosis - Why is it dangerous?

Infection with the Legionella bacteria can lead to a disease called Legionnaires' disease. There are two main forms:

• Legionnaires' disease - a severe form of pneumonia that may require hospitalization, and
• Pontiac fever - a milder form, resembling the flu.

Symptoms may include:

• High fever,
• cough and shortness of breath,
• muscle aches,
• general weakness.

The elderly, those with weakened immune systems, smokers, and those with chronic illnesses are most at risk. It's worth emphasizing that the disease is not transmitted from person to person – the source of infection is the environment.

Where is the greatest risk?

Although Legionella can appear in many places, it's worth paying particular attention to:

• hot water systems,
• showers and water faucets,
• cooling towers and air conditioning systems,
• swimming pools, spas, jacuzzis,
• water tanks and heaters.

The risk increases wherever water comes into contact with air and can create aerosols.

Why is Legionella testing so important?

The presence of Legionella cannot be detected with the naked eye – water can be clear and seemingly clean. Therefore, the only effective way to control it is through regular microbiological testing.

Testing allows:

• to detect the presence of bacteria in the system,
• to assess the level of contamination,
• to take preventive measures before a real threat occurs.

In many facilities (e.g., hospitals and hotels), Legionella monitoring is mandatory. Increasingly, residential building owners and property managers are also choosing to do so.

How to prevent Legionella growth?

The good news is that Legionella growth can be effectively limited. Preventive measures are crucial:

• maintaining the appropriate water temperature (warmth above 55°C),
• regularly flushing the system,
• avoiding water stagnation,
• cleaning and disinfecting the system,
• inspecting the technical condition of the system.

In practice, this means that even simple measures – such as regularly using infrequently used water points – can make a difference.

Summary

Legionella is an example of a microorganism that demonstrates the importance of monitoring water quality, not only chemically but also microbiologically. Although the threat is invisible, its consequences can be serious.

Therefore, regular water testing and appropriate preventive measures are not just a matter of meeting requirements – they are, above all, a real contribution to user safety. In a world where we increasingly prioritize quality of life, it's worth remembering that clean water means not only the absence of contaminants visible to the naked eye, but also the absence of those invisible to the naked eye.