[Translate to english:] Legionellen


Testing for bacterial burden in water installations

Legionella are bacteria that occur naturally in open bodies of water and drinking water. They occur primarily in locations where warm water provides the optimum conditions for their multiplication. As a result, any warm water installation could be affected, such as hot water pipes, hot water tanks or boilers. 

Depending on the concentration of the bacteria (inhaled as aerosols/droplets), they can lead to illnesses. 

A high number of legionella bacteria in water will mean a high risk of infection for particular categories of people. The Swiss Federal Office for Public Health (BAG) has proposed limit values for sanitary installations above which, a reduction in the legionella burden is recommended and/or is urgently necessary. 

As an accredited Swiss contract laboratory, we can provide you with technically correct sampling in accordance with ISO 19458 and the investigation of water samples for legionella bacteria. 

Retirement homes, public baths, schools, hotels, service areas and the owners and administrators of detached houses and apartment blocks can take advantage of our services. 

Can we help you?
We’d be pleased to advise you.

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Head of Order Management Food & Feed Services

Sascha Theobald

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What are legionella?

Legionella - with the type considered to be the most dangerous L. pneumophila - are rod-shaped bacteria that occur in water. They can multiply best at a temperature range between 25 and 45 °C and can survive for a short time temperatures of 60 °C. Under 20 °C, almost no legionella multiplication takes place. Legionella do not cause disease when in drinking water or from skin contact. If however, they are inhaled as an aerosol in small water droplets, they can lead to legionellosis (also called “Legionnaire’s disease”) by colonising the lung tissue.

Legionella can also get into the lungs as an aerosol, e.g. when showering
Legionella can also get into the lungs as an aerosol, e.g. when showering

Incidence rates

The rate of disease is approximately 2 people per 100,000 inhabitants with a confirmed diagnosis of pronounced Legionnaire’s disease which leads to death in over 5 % of cases. Additionally, there are a very large number of unknown cases of a milder form of the disease which appear as flu-like illnesses (Pontiac fever).

There are regular occurrences of high levels of illnesses (locally restricted epidemics) due to massively contaminated warm water systems (air conditioning systems, cooling towers, swimming pools and others similar facilities).

This occurs because an increased concentration of legionella in aerosol form means the risk of infection also increases. 

Examples of the incidence of legionella

  • Water heating and hot water distribution systems
  • Swimming pools
  • Air washers in air conditioners
  • Cooling towers
  • Biofilms
  • Hospitals
  • School showers and other public showers
  • Bathtubs, ward baths
  • Unused pipes
  • Water tanks
  • Cold water supply lines to thermostatic mixing valves
  • Cold water supply lines with a warming influence from outside or with long periods of inactivity, e.g. infrequently used fire-extinguishing pipelines with a connection for drinking water


In what cases is it sensible to test for legionella?

In Switzerland, it is not currently mandatory to investigate for legionella. Monitoring of the legionella status is however strongly recommended as part of the duty of care for retirement and care homes, for public facilities with warm water baths at an increased risk (spas and whirlpools) as well as hotels. The Swiss Federal Office for Public Health has defined limit and tolerance values for these installations and corrective measures must be taken if these values are exceeded.

For water heating systems in apartment buildings and blocks of flats and also in private houses, monitoring is particularly recommended if the temperature in the hot water system cannot be kept or is not kept permanently above 60 °C. The Swiss Federal Office for Public Health has also published limit values for these installations.

Germ count determination of legionella in the microbiological laboratory
Germ count determination of legionella in the microbiological laboratory

How should samples be taken?

Depending on the purpose of the investigation (monitoring of the sampling point, of the pipeline system or of the functioning of the water heaters), appropriate and representative sampling must be performed. The trained sample takers from UFAG Laboratorien AG will be pleased to provide support here so that the microbiological water investigations can provide a clear statement over the condition of the water heating facilities. The basis for sample taking is described in the Swiss EN ISO 19458 standard. If you are in the position to be able to take the samples yourself, then we can provide you with the sample containers (sterile disposable bottles).

Assessing the results of the legionella investigation analyses

The complete absence of legionella in water cannot be achieved at a reasonable expense. Complete absence is however not necessary, because the risk of infection is low when there is only a small number of bacteria.

We can advise you on the basis of the recommendations of the Swiss Federal Office for Public Health (BAG) whether you should be considering decontamination. If desired, we would be pleased to provide contacts to specialist companies that can provide support for this. 


Our services in detail:

  • Consultation on the determination of legionella
  • Bacteria count determination of legionella
  • Additional services are according to the directory of services or upon request.
Legionella: Rod-shaped bacteria
Legionella: Rod-shaped bacteria

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