Clarifying the cause

Cooling tower was the source of the legionella infections

Legionella multiply in water.

(Bild: Manuel Schwaiger)

A heavily contaminated cooling tower at a plant in the Lower Rhine Valley was shut down 14 days ago and there have been no new cases since Tuesday. A total of 47 people were infected with legionella. 

Since the beginning of the year, there has been an increase in legionella infections in the Vorarlberg lowlands, with a total of 47 cases. In the search for the source of the germs, a cooling tower at a plant came under suspicion, which was shut down 14 days ago and extensively renovated. The fact that the last two new cases were reported at the beginning of this week now indicates "that the identified source is highly likely to be correct", the state said on Friday.

Similarities identified
Due to the incubation period of Legionnaires' disease of two to ten days, the illnesses were not expected to end immediately, it said. The state's environmental institute had detected contamination in several households and cooling towers during its search for the cause. An analysis of the Legionella strains detected in infected persons revealed a genetic relationship. It is therefore assumed that they may have been infected by the same source of infection. The sequencing results and environmental samples subsequently showed similarities: The same Legionella type was detected in the cooling tower of the operating plant in the Lower Rhine Valley.

The possible source of the germs was thus found. However, the state stated that it was necessary to wait and see whether there were any other sources. The last two cases were reported at the beginning of the week, the onset of illness in both people was around two weeks ago. There have been no new cases since then. However, it is possible that there could be further isolated cases because some people only develop symptoms later or there could be other sources. The Environmental Institute will therefore take samples from other possible sources.

Nebulized water
The pathogen that causes Legionella pneumophila, the Legionella pneumophila bacterium, is transmitted through nebulized water. The droplets containing the pathogen can spread in the air and be inhaled. Possible sources of infection are showers, humidifiers, taps, cooling towers or air conditioning systems. Transmission is also possible in swimming pools via waterfalls, slides, whirlpools and fountains.

Legionella causes two different diseases in humans: Legionnaires' disease and Pontiac fever. The former is a severe pneumonia. Pontiac fever has a milder course with flu-like symptoms and usually heals on its own. In the current outbreak in Vorarlberg, two people had a severe course of the disease.