Legionellae – tiny germs in steam


Many people have a similar ritual every morning: wash, shower, have breakfast, clean their teeth and off to work. Hardly anybody is aware that they may already be exposing themselves to danger when they are whistling their favourite tune under the shower.

The invisible pathogens

Legionella bacteria can become a real problem. That’s no reason for any of us to panic. But fine steam from the shower or a slight mist over the water surface of the whirlpool bath provides ideal conditions for these invisible pathogens to get into our bodies. The bacteria measuring just 2 to 6 micrometres get into our organism by inhalation. There legionella pneumophila can cause diseases such as legionellosis, better known as Legionnaires’ disease. It is the most frequent form of legionellosis and, in addition to flu-like symptoms, can lead to pneumonia. By the way, the name “Legionnaires’ disease” goes back to an American Legion convention in Philadelphia, USA, where several attendees contracted the disease through contaminated air-conditioning systems. It is above all older people or those with a weakened immune system who are generally prone to the infection.

Legionnaires’ disease is the most common and also most dangerous form of legionellosis, accounting for 90% of cases.

Natural environment

Legionella bacteria are found all over the world and occur in natural fresh water biotopes. They are therefore also present in small amounts in groundwater and surface waters. They can, for example, also be present in any lake where you take a dip on sunny days. However, here you do not generally have to worry about getting an infection. The bacteria do not multiple freely in such waters but increase their population through intracellular replication in amoebae or other unicellular organisms.

A breeding ground in the system

Legionellen unter der Lupe

The bacteria multiple rapidly in water at warm temperatures between 25 and 45° Celsius and are only killed at temperatures of 60° Celsius upwards. Stagnant water, such as is found in water tanks or water pipes, can form a biofilm and therefore a small habitat producing a higher concentration of these germs. Therefore, in the event of contamination with legionella, a specialist company has to flush all draw-off points over a prolonged period in complex procedures using over 70° Celsius hot water in order to drive the bacteria out of the artificial biotope. It is not possible for the owner of the water system to do this themselves as hot water boilers normally do not have the necessary capacity.

Legionella infections in Europe

In Germany, it is estimated that up to 30,000 people contract legionellosis every year. However, according to the Robert Koch Institute, only very few cases are reported – in 2016 it was only 710 cases. One reason for the drastic difference may be that not every patient with pneumonia is tested for legionella bacteria. In the summer months, the number of reported cases increases, which can be linked to the holiday season and the consequent increased number of trips abroad or the more frequent use of air-conditioning systems.

The EU is also aware of this issue. For example, the European Centre of Disease Prevention and Control, which is based in Sweden, reported a total of 6,573 infections per 100,000 inhabitants from the European region in 2015. 881 cases were reported in Germany, while 1,556 infections, that is to say nearly twice as many, were registered in Italy.

ista tests drinking water systems

In view of the potentially serious consequences, in Germany there has been a notification and testing obligation for large-scale drinking water heating systems since 2001. The Drinking Water Ordinance has been revised several times since then – most recently in December 2012. According to the latest version, the systems in public buildings have to be tested at least once a year while those in commercially used buildings and apartment buildings must be tested at least every three years. The systems in single and two-family buildings and the drinking water heating systems of condominiums in which none of the units are rented out do not count as large-scale systems and are therefore not subject to the obligation to test for legionella. However, if you want to be on the safe side, you can still have such a drinking water analysis conducted.

After all, ten per cent of the private drinking water systems tested by ista in the last five years exceeded the maximum acceptable legionella concentration of 100 CFU (colony-forming units) per 100 ml of water!

The maximum acceptable legionella concentration for drinking water is 100 CFU per 100 ml of water!

It’s a landlord’s obligation

As a landlord and therefore property owner, you are obliged to have the apartments you rent out tested for possible legionella contamination. If the maximum acceptable levels are exceeded, this can not only put people’s health at risk, as already mentioned, but also cause legal problems for the owner. Under the Drinking Water Ordinance, he is obliged to test for legionella. In the event of definite contamination, rent reductions or compensation payments are the least of his worries. Only just back in 2008, a man died in Berlin of pneumonia caused by legionella bacteria. The landlord was then sued for compensation and damages for pain and suffering to the tune of € 23,000. Therefore, regular checks not only protect the person responsible but can also even save lives. With the ista drinking water analysis, such exceedance of maximum acceptable concentrations can be detected at an early stage.

Take samples and then what …?

But how is a drinking water analysis actually performed? In the first step, samples are taken from the drinking water system. They are analysed and in the best-case scenario found to be free of the rod-shaped bacteria. However, if this is not the case, the health authorities have to be notified. Then further, more in-depth tests are performed. Hazard analyses show the causes of the contamination before action is ultimately taken to eradicate the legionella bacteria.

Testing of possible legionella contamination
The drinking water analysis in 5 steps: (1) Sample-taking (2) Analysis (3) Notification (4) Hazard analysis (5) Eradication

Thermal disinfection at temperatures of over 70° Celsius should, however, only be performed by specialists. The same applies to so-called chlorination where the entire system is disinfected using chlorine. Once the drinking water system is free of legionella bacteria, checks are again performed and everything documented. Under the Drinking Water Ordinance, all documents have to be kept for 10 years.

Early detection of sources of infection

The rod-shaped bacteria primarily enter our bodies through the air we breathe. So showering in particular, but also the use of air-conditioning systems can become a real danger. Therefore, a regular, professional examination of drinking water systems is definitely to be recommended. After all, we should be able to continue getting off to a perfect start to the day by whistling our favourite tunes under the shower without any worries!

Picture credits: Shutterstock/SasinParaksa

Picture credits: Shutterstock/Jordi Prat Puig