Surveillance Open Access
Like 0



The burden of Legionnaires’ disease (LD) in the European Union/European Economic Area (EU/EEA) has increased during the last decade, with notification rates increasing from 1.2 to 1.4/100,000 population in 2012–16, to 1.8–2.2 within 2017–19.


To measure weekly excess cases during 2017–19 based on previous trends and determine whether a significant change in trend occurred, and to examine any differences in age, sex or level of imported infections.


We collated 2012–19 annual surveillance data from The European Surveillance System (TESSy) reported by EU/EEA countries. A retrospective prediction by a dynamic regression model was created from 2012–16 data to assess excess cases in 2017–19. Interrupted time series (ITS) analysis was performed to determine if a significant change in trend occurred in 2017–19 compared with the previous 5 years.


We found a 33.9% increase in cases in 2017–19 compared with the number predicted. The ITS also found a significant trend increase in 2017–19 compared with 2012–16. A significant trend increase was observed from 2017 most strongly among older age groups (> 60 years) and non-imported cases.


Our study showed a significant increasing trend in LD cases in the EU/EEA during 2017–19 compared with the previous 5 years. The distribution of cases per week suggests an overall amplification of the seasonal trends. These findings underscore that LD continues to be an infectious disease of public health concern in the EU/EEA, warranting further research into determinants of the increase.


Article metrics loading...

Loading full text...

Full text loading...



  1. Cunha BA, Burillo A, Bouza E. Legionnaires’ disease. Lancet. 2016;387(10016):376-85.  https://doi.org/10.1016/S0140-6736(15)60078-2  PMID: 26231463 
  2. European Centre for Disease Prevention and Control (ECDC). Legionnaires’ disease: Annual Epidemiological Report for 2016. Stockholm: ECDC; 2018. Available from: https://www.ecdc.europa.eu/en/publications-data/legionnaires-disease-annual-epidemiological-report-2016
  3. European Centre for Disease Prevention and Control (ECDC). Legionnaires’ disease: Annual Epidemiological Report for 2019. Stockholm: ECDC; 2021. Available from: https://www.ecdc.europa.eu/en/publications-data/legionnaires-disease-annual-epidemiological-report-2019
  4. European Centre for Disease Prevention and Control (ECDC). Legionnaires’ disease: Annual Epidemiological Report for 2020. Stockholm: ECDC; 2022. Available from: https://www.ecdc.europa.eu/en/publications-data/legionnaires-disease-annual-epidemiological-report-2020
  5. European Centre for Disease Prevention and Control (ECDC). TESSy metadata report. Stockholm: ECDC; 2022. Available from: https://www.ecdc.europa.eu/en/publications-data/tessy-metadata-report
  6. Hyndman RJ, Athanasopoulos G. Forecasting: principles and practice. 3d ed. Melbourne, Australia: OTexts; 2021.
  7. De Livera AM, Hyndman RJ, Snyder RD. Forecasting time series with complex seasonal patterns using exponential smoothing. J Am Stat Assoc. 2011;106(496):1513-27.  https://doi.org/10.1198/jasa.2011.tm09771 
  8. R Core Team. R: A language and environment for statistical computing. Vienna, Austria: R Foundation for Statistical Computing; 2021. Available from: https://www.R-project.org
  9. Bernal JL, Cummins S, Gasparrini A. Interrupted time series regression for the evaluation of public health interventions: a tutorial. Int J Epidemiol. 2017;46(1):348-55.  https://doi.org/10.1093/ije/dyw098  PMID: 27283160 
  10. Wang E, Cook D, Hyndman RJ. A new tidy data structure to support exploration and modeling of temporal data. J Comput Graph Stat. 2020;29(3):13.  https://doi.org/10.1080/10618600.2019.1695624 
  11. George F, Shivaji T, Pinto CS, Serra LAO, Valente J, Albuquerque MJ, et al. A large outbreak of Legionnaires’ Disease in an industrial town in Portugal. Rev Port Saude Publica. 2016;34(3):199-208.  https://doi.org/10.1016/j.rpsp.2016.10.001 
  12. European Centre for Disease Prevention and Control (ECDC). Legionnaires’ disease: Annual Epidemiological Report for 2018. Stockholm: ECDC; 2020. Available from: https://www.ecdc.europa.eu/en/publications-data/legionnaires-disease-annual-epidemiological-report-2018
  13. Buchholz U, Altmann D, Brodhun B. Differential seasonality of Legionnaires’ disease by exposure category. Int J Environ Res Public Health. 2020;17(9):3049.  https://doi.org/10.3390/ijerph17093049  PMID: 32353925 
  14. Barskey AE, Derado G, Edens C. Rising incidence of Legionnaires’ disease and associated epidemiologic patterns, United States, 1992-2018. Emerg Infect Dis. 2022;28(3):527-38.  https://doi.org/10.3201/eid2803.211435  PMID: 35195513 
  15. Eurostat Statistics Explained. Population structure and ageing. Section: The share of elderly people continues to increase. Luxembourg: European Commission; 2022. Available from: https://ec.europa.eu/eurostat/statistics-explained/index.php/Population_structure_and_ageing
  16. Eurostat Statistics Explained. Ageing Europe - statistics on population developments. Section: Older people – differences between the sexes. Luxembourg: European Commission; 2020. Available from: https://ec.europa.eu/eurostat/statistics-explained/index.php/Ageing_Europe_-_statistics_on_population_developments
  17. Cassell K, Thomas-Lopez D, Kjelsø C, Uldum S. Provincial trends in Legionnaires’ disease are not explained by population structure in Denmark, 2015 to 2018. Euro Surveill. 2021;26(25):2000036.  https://doi.org/10.2807/1560-7917.ES.2021.26.25.2000036  PMID: 34169817 
  18. Eurostat Statistics Explained. Tourism statistics - nights spent at tourist accommodation establishments, EU, 2009-2022. Luxembourg: European Commission. [Accessed: 14 Mar 2023]. Available from: https://ec.europa.eu/eurostat/statistics-explained/index.php?title=Tourism_statistics_-_nights_spent_at_tourist_accommodation_establishments&stable=1
  19. Lanternier F, Ader F, Pilmis B, Catherinot E, Jarraud S, Lortholary O. Legionnaire’s disease in compromised hosts. Infect Dis Clin North Am. 2017;31(1):123-35.  https://doi.org/10.1016/j.idc.2016.10.014  PMID: 28159172 
  20. Dyba T, Randi G, Bray F, Martos C, Giusti F, Nicholson N, et al. The European cancer burden in 2020: Incidence and mortality estimates for 40 countries and 25 major cancers. Eur J Cancer. 2021;157:308-47.  https://doi.org/10.1016/j.ejca.2021.07.039  PMID: 34560371 
  21. Pampaka D, Gómez-Barroso D, López-Perea N, Carmona R, Portero RC. Meteorological conditions and Legionnaires’ disease sporadic cases-a systematic review. Environ Res. 2022;214(Pt 4):114080.  https://doi.org/10.1016/j.envres.2022.114080  PMID: 35964674 
  22. Brandsema PS, Euser SM, Karagiannis I, Den Boer JW, Van Der Hoek W. Summer increase of Legionnaires’ disease 2010 in The Netherlands associated with weather conditions and implications for source finding. Epidemiol Infect. 2014;142(11):2360-71.  https://doi.org/10.1017/S0950268813003476  PMID: 24576486 
  23. Braeye T, Echahidi F, Meghraoui A, Laisnez V, Hens N. Short-term associations between Legionnaires’ disease incidence and meteorological variables in Belgium, 2011-2019. Epidemiol Infect. 2020;148:e150.  https://doi.org/10.1017/S0950268820000886  PMID: 32345387 
  24. Intergovernmental Panel on Climate Change (IPCC). Sixth assessment report. August 2021. Working Group 1: The Physical Science Basis. Regional Fact Sheet- Europe. Geneva: IPCC; 2021. Available from: https://www.ipcc.ch/report/ar6/wg1/downloads/factsheets/IPCC_AR6_WGI_Regional_Fact_Sheet_Europe.pdf
  25. World Meteorological Organisation (WMO). State of the Climate in Europe 2021. No.1304. Geneva: WMO; 2022. Available from: https://library.wmo.int/doc_num.php?explnum_id=11378
  26. Copernicus Climate Change Service. European State of the Climate 2019. Reading, UK: Copernicus; 2019. Available from: https://climate.copernicus.eu/sites/default/files/2020-04/ESOTC2019_summary.pdf
  27. European Environment Agency (EEA). EEA Report No 07/2022. Climate change as a threat to health and well-being in Europe: focus on heat and infectious diseases. Copenhagen: EEA; 2022. Available from: https://www.eea.europa.eu/publications/climate-change-impacts-on-health
  28. Rhoads WJ, Ji P, Pruden A, Edwards MA. Water heater temperature set point and water use patterns influence Legionella pneumophila and associated microorganisms at the tap. Microbiome. 2015;3(1):67.  https://doi.org/10.1186/s40168-015-0134-1  PMID: 26627188 
  29. Proctor CR, Dai D, Edwards MA, Pruden A. Interactive effects of temperature, organic carbon, and pipe material on microbiota composition and Legionella pneumophila in hot water plumbing systems. Microbiome. 2017;5(1):130.  https://doi.org/10.1186/s40168-017-0348-5  PMID: 28978350 

Data & Media loading...

Supplementary data

Submit comment
Comment moderation successfully completed
This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error