Information on Legionella diseases

Changed on: 13.03.2018

The number of people in Europe suffering from Legionnaires’ disease (legionellosis) has increased in recent years. According to the European Centre for Disease Prevention and Control (ECDC), 7069 cases were reported in Europe in 2016 (compared with 5830 cases reported in 2013).
The number of cases has also risen in Austria: 100 cases of Legionnaires’ disease were documented in 2013, and 218 were documented in 2017 (out of a population of 8.772 million). In comparison, 490 cases in a population of 8.372 million were documented in Switzerland in 2017. Legionnaires’ disease is a severe, sometimes fatal pneumonia caused by bacteria of the genus Legionella (most common species: Legionella pneumophila). Although the number of Legionella outbreaks has remained constant over the years, the number of cases of Legionnaires’ disease has risen sharply.

Several factors are likely to be responsible for the increase in the number of cases in Austria:

  • An increase in the detection rate of cases of Legionnaires’ disease in patients with pneumonia as a result of the increased use of rapid tests (qualitative detection of the Legionella pneumophila antigen in the urine samples of patients)
  • The increased reporting of cases of Legionnaires’ disease through the electronic laboratory reporting obligation that has been in force since the beginning of 2014
  • An actual increase in the number of Legionella cases as a result of global climate change is being debated. In 2014, a connection between a particularly warm, humid summer and an increased number of cases was observed in the Netherlands and England. In the spring and summer of 2017, the number of cases of Legionnaires’ disease reported was up to 40% higher than expected in many European countries, including Austria.

The Austrian Society for Infectious Diseases and Tropical Medicine (ÖGIT) and AGES have taken measures to raise awareness of this disease. A new ÖGIT guideline aims to optimise the diagnosis, treatment, and prevention of the disease. As the National Reference Centre for Legionella Infections, AGES conducts training courses for public health officials as well as other staff of health authorities and associated institutions in cooperation with the regional health authorities:

7 March 2018: Sampling for Legionella and food-borne infections

A Legionella infection is caused by inhaling aerosols (i.e. ultra-fine water droplets) or ultra-fine dust particles contaminated with Legionella. Drinking water that contains Legionella does not pose a health risk. Smokers as well as individuals with weakened immune systems and chronic lung diseases are at risk. Transmission from person to person has not yet been proven.

Legionella tends to proliferate in the complex water systems of large buildings (e.g. hospitals/nursing homes, tourist accommodation, and swimming pools). However, these bacteria can also be found in the water supply systems of residential complexes and other water-containing systems (e.g. cooling towers, whirlpools, humidification systems, decorative fountains, and car washes as well as natural thermal springs and their distribution systems) and multiply to numbers that are unsafe for humans. At temperatures between 25 and 45°C and in stagnant water, Legionella multiplies in biofilms (i.e. layers of slime in which micro-organisms are embedded). Only at temperatures above 60°C do Legionella die off quickly.


Legionnaires’ disease in Austria
Year Cases of LegionellaOf which deathsCase mortality rate
20131001414 %
2014135128,9 %
201516063,8 %
201616174,3 %
2017218104,6 %