Legionella in drinking water - occurrence, hazards and disposal

Legionella, the cause of the so-called Legionnaire's disease, can pose a serious health hazard. Again and again, there are deaths from legionella in drinking water. Legionella's biological properties, where exactly dangers exist, and how they can be eliminated are therefore explained in detail here.

Biological properties

Legionella are rod-shaped bacteria. Through their scourges they are able to move on their own. Legionella belong to the gram-negative bacteria.

Legionella need certain living conditions in order to multiply. These are:

  • warm water (fresh water or salt water)
  • a temperature range between about 25° C and 50° C - above and below they are not viable
  • regular water change (fresh water)
  • as little water movement as possible (stay in one place)

These conditions are always there where hot water treatment takes place. But there is also a risk in the tanks for air conditioners, in bathrooms and showers and cooling towers.

There is also a certain risk in water pipes with low extraction. Legionella can also survive well in so-called biofilms, slimy deposits of different types of bacteria on the wall of water pipes.

Dangerous species

The vast majority of the 48 legionella species is harmless to humans. Only Legionella pneumophilia is responsible for infections. However, L.pneumophilia is the most abundant species, accounting for almost 90% of all legionella in our environment.

Caused diseases

The disease mainly caused by Legionella is the Legionellosis or Legionnaire's disease.

It is always caused when legionella is inhaled. This happens wherever previously standing water, in which Legionella are located, is atomised:

  • in the shower
  • through lawn sprinkler
  • by air conditioning
  • by humidifier
  • through whirlpools
  • through mist basin

If the Legionella get into the deeper lung areas, this can cause severe bacterial pneumonia (pneumonia). This pneumonia can also be fatal.

Legionella are with up to 10% of the most common pathogens of pneumonia.

Risk groups for legionellosis

People with an intact immune system and intact lung function are usually only slightly endangered. Here also rarely occurs in existing legionella infection.

People with a weak immune system, smokers and people with kidney failure (renal insufficiency) are particularly susceptible to infections. In addition, also people who already have damage to the heart or lungs.

The most common infections so far involve middle-aged men. They get about two to three times as likely as women. In principle, however, legionellosis can occur at any age and in any gender, if the conditions are correspondingly unfavorable.

The legionellosis got her name because of her first appearance at a veterans congress in the United States 1976th There died 29 men out of 180 patients.

In general, it can be assumed that infections in people without impairments have a mortality rate of around 15 percent - in people with pre-existing diseases of the heart, lungs or kidneys, however, the mortality risk is just under 70 percent.

Pontiac fever

Pontiac fever is a disease also caused by legionella, but less dramatic and without pneumonia. The disease is similar to flu and has never before led to death.

Inflammation outside the lungs

Inflammation of the pericardium (endocarditis), pyelonephritis and wound infection by legionella have also been reported in a few cases. Although they sometimes take a difficult course, but are still easy to treat.

Treatment of Legionella infections

For the treatment of legionellosis antibiotics are available. Erythromycin is one of the first-choice antibiotics, and there are a number of broadband products to choose from that are also effective in legionellosis.

compulsory registration

Any detected Legionella disease must be reported by the laboratory that is diagnosing. The number of cases is constantly increasing, with 917 cases reported in 2013. In the previous year, it was one third less.

Verification obligation

According to the Drinking Water Ordinance, every major operator of water heaters must have an annual check on Legionella when the water is released in the commercial or public sector and is atomised.

This affects, among other things, kindergartens and schools. Since the end of 2011, property management companies, owners of multi-family houses and housing associations have had to carry out investigations. Here the examination interval is three years.

From a certain amount of Legionella further investigations, hazard analyzes and renovations are occasionally necessary and legally required.

Protection against Legionella

Various measures are possible for the killing of possibly existing Legionella cultures in water tanks.

If drinking water is stored cool - below 25° C - Legionella can not multiply and die off slowly.

Another possibility may be the regular warming of the water. This happens, for example, by so-called "legionella circuits". The problem is, however, that at high [water hardness] water hardness by heating a lot of lime is precipitated.

Disinfection measures, ultrafiltration, but also the use of hypochlorous acids are immediate measures that make sense only in case of a correspondingly high infestation.

Tips & Tricks

In many southern countries there is no protection against Legionella as in Germany. In addition, there are often structural deficiencies and generally very favorable for Legionella temperature. So be careful here.

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