Legionella bacteria occur naturally in soil and water. When water heats up, the bacteria can spread through the tap water. People can then become ill by breathing in the mist of this contaminated water.
For example, through the mist from a shower, sauna, whirlpool, bubble bath, sprinkler system or fountain. It can also come from mist from high-pressure jets, car washes, events with water attractions, air humidification systems (apnea equipment!), plant sprinklers, gardening and splashing rainwater. Humid weather conditions also seem to have an influence. People do not get legionella contamination by drinking this water.
Legionella bacteria can grow very quickly in warm water. Especially if the water temperature is between 20°C and 50°C.


Legionnaires' disease (legionellosis)
The Legionella bacteria (Legionella pneumophila) can cause Legionnaires' disease (legionellosis), which may be accompanied by rapidly developing headache, muscle pain, joint pain, pneumonia with high fever (above 39°C), chills, shortness of breath, rapid breathing and a dry cough. People can be severely ill. Some have diarrhea and vomiting. Some people die from this disease.
People with Legionnaires' disease cannot infect others.


The time between the infection and the first complaints (incubation period) varies from two to twenty days, but is on average one week.
Some people are more vulnerable to getting sick:

  • elderly people
  • people in poor health
  • people who use medications that weaken their immune system
  • smokers

In case neurological complaints occur with a pneumonia, the doctor must be alert to the possibility of a legionella contamination.


Neurological complaints in pneumonia

It is not generally known that the Legionella bacteria can also cause neurological complaints. Yet it happens a lot. A CT scan or MRI scan cannot always provide clarity. Sometimes the scan shows reduced blood flow or (reversible) damage (hyperintensity) in the white matter or in the brain area (corpus callosum). Reversible injury means that the injury can recover. Legionella is almost never found in the spinal fluid.


Possible neurological findings


Reported neurological complaints with legionella infection

  • Headache
  • Dysarthria, difficulty articulating, difficulty speaking
  • Choppy speech, different 'melody' of the speech, slowed pace
  • Ataxia, coordination disorder, difficulty walking and trunk ataxia
  • Involuntary tremor, intention tremor, shaking, trembling or trembling
  • Eye complaints: gaze paralysis and downward nystagmus (wobbling eyes where in this case the movement goes up and down)
  • Pronounced complaints of cerebellar involvement
  • Amnesia
  • Disorientation, confusion with possible "floppy" behavior

*NB! Not all complaints need to occur.


Reversible complaints with recovery and long-term or permanent complaints

In many people, after treatment with antibiotics, the neurological complaints turned out to be temporary in nature and after a period of time the scan no longer showed any abnormalities.

After months, recovery of walking and talking was reported. Recovery can take a long time, ranging from months to years.

For some, neurological complaints turned out to be long-lasting or even permanent. In that case, one will speak of brain damage or NAH (Non-Congenital Brain Injury). 
One must be alert to the invisible consequences of brain injury.


HUS (Hemolytic Uremic Syndrome)

HUS, Hemolytic Uremic Syndrome, is usually caused by (intestinal) bacteria and viruses.


  • Accelerated breakdown of red blood cells (hemolysis)
  • Deficiency of platelets
  • Poor kidney function/kidney failure (uremia)


The bacteria and viruses can destroy the red blood cells in the blood. This causes a shortage of red blood cells. The lining of the blood vessels (the endothelium) can become damaged, causing platelets to clump and blood clots to form in the blood. The kidneys also no longer function properly because the urea level increases.

Urea is a substance that is normally filtered from the blood by the kidneys. The blood clots can cause cerebral infarctions, but can also damage the kidneys (thrombotic microangiopathy).
The body reacts so strongly because the substance toxin is produced. It mainly happens with verotoxin and Shiga toxin.


HUS due to legionella infection

HUS, without production of toxins (atypical HUS / aHUS) can,
among other things, caused by the Legionella bacteria. This also causes intense disruption of the body's immune system. In atypical HUS, blood clots can develop with the risk of cerebral infarction or kidney damage. The red blood cells can also break down and damage the inner lining of the blood vessels.

Read more about HUS.


Tips to prevent legionella bacteria in your tap water:

  1. Prevent stagnant water in warm environments
  2. Set the temperature of the boiler or central heating boiler to at least 55⁰. The bacteria are killed at temperatures above 60⁰.
  3. Use all taps in the house at least once a week.
  4. After the holiday, rinse the pipes in the house thoroughly. Prevent inhalation of water spray during flushing by immersing the shower head in a bucket of water or in the sink with the stopper in place. Otherwise, keep the shower head close to the drain.
  5. If you are on holiday and you suspect that the taps have not been used for a while, also flush the pipes, as described under 4.
  6. Rinse garden hoses and high-pressure hoses thoroughly after use.
  7. Clean humidifiers every week and fill them with fresh water. Make sure the water has boiled so that all bacteria are killed.
  8. Also pay attention to self-made showers from a water bag at the campsite.

See also here 


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