Impact of lockdown and non-pharmaceutical interventions on the epidemiology of Legionnaires’ disease: Legionnaire’s disease and COVID-19

Impact of lockdown and non-pharmaceutical interventions on the epidemiology of Legionnaires’ disease

Legionnaire’s disease and COVID-19


  • Matteo Riccò Azienda USL di Reggio EmiliaV.le Amendola n.2 - 42122 REServizio di Prevenzione e Sicurezza negli Ambienti di Lavoro (SPSAL)Dip. di Prevenzione


Legionella, Legionnaires’ disease, non-pharmaceutical interventions, COVID-19


Background and aim. In order to cope with the requirements of COVID-19 pandemic and prevent overwhelming of the healthcare systems, during 2020 social distancing measures were proposed, and generalized lockdown. Aim of our study is to ascertain whether non-pharmaceutical intervention did have any impact on the epidemiology of Legionnaires’ disease (LD), a respiratory infectious disease without interhuman spreading.

Methods. Official national reports from 4 index countries in European Union (i.e. Germany, France, Italy, and Spain) were retrieved. The study included all cases notified during 2020 COVID-19 outbreak, versus the cases referred during the same period in 2019. Subgroup analyses for hospital-associated and travel-associated LD cases, as well as for lethality estimates were performed.

Results. A sustained drop for incidence rate was confirmed, at EU-level (3.5 per 100,000 vs. 5.3 per 100,000) as well as in the national estimates. The decrease was particularly evident in Italy (RR 0.880, 95%CI 0.839 to 0.905), despite a transient surge in notification rates during the month of June, 2020. Subgroup analyses demonstrated a fall in travel-associated cases (-66.8% at EU level), while hospital-associated cases decreased in absolute number when compared to 2019, but where substantially stable in terms when compared to EU estimates. While Case Fatality Ratio increased in comparison with 2019, no significant trend was similarly identified in comparison to EU estimates.

 Conclusions. Lockdown measures have impacted on the epidemiology of LD in Europe during 2020, but some heterogeneities were identified both across the assessed countries, and the various subgroup. Even though the absolute number of total cases did substantially decrease in 2020 compared to 2019, the effect of non-pharmaceutical interventions was mostly indirect, through a reduced interaction of individuals with environments at potentially high-risk for human infections (e.g. hospitals, accommodation sites, etc.).

Author Biography

Matteo Riccò, Azienda USL di Reggio EmiliaV.le Amendola n.2 - 42122 REServizio di Prevenzione e Sicurezza negli Ambienti di Lavoro (SPSAL)Dip. di Prevenzione

Dipartimento di Sanità Pubblica

Dirigente Medico di Medicina del Lavoro


Flaxman S, Mishra S, Gandy A, Unwin HJT, Mellan TA, Coupland H, et al. Estimating the effects of non-pharmaceutical interventions on COVID-19 in Europe. Nature 2020;584:257–61.

Müller O, Razum O, Jahn A. Effects of non-pharmaceutical interventions against COVID-19 on the incidence of other diseases. The Lancet Regional Health - Europe 2021;6:100139.

Riccò M, Peruzzi S, Balzarini F. Public perceptions on non-pharmaceutical interventions for west nile virus infections: A survey from an endemic area in Northern Italy. Trop Med Infect Dis 2021;6:116.

Hall CB, Weinberg GA, Iwane MK, Blumkin AK, Edwards KM, Staat MA, et al. The Burden of Respiratory Syncytial Virus Infection in Young Children. New England Journal of Medicine 2009;360:588–98.

Hall CB. Respiratory Syncytial Virus and Parainfluenza Virus. N Engl J Med 2001;344:1917–26.

Ullrich A, Schranz M, Rexroth U, Hamouda O, Schaade L, Diercke M, et al. Impact of the COVID-19 pandemic and associated non-pharmaceutical interventions on other notifiable infectious diseases in Germany: An analysis of national surveillance data during week 1–2016 – week 32–2020. The Lancet Regional Health - Europe 2021;6:100103.

Bonita Brodhun, Udo Buchholz. Legionarskrankheit in Deutschland - 2010 bis 2020. vol. 2021. Berlin: 2021.

Direction des maladies infectieuses, Santé Publique France. Bilan des cas de légionellose notifiés en France en 2020. Paris: 2021.

Rota MC, Caporali MG, Bella A, Scaturro M, Giannitelli S, Ricci ML. I risultati del sistema di sorveglianza della legionellosi in Italia nel 2020 durante la pandemia di COVID-19. Boll Epidemiol Naz 2021;2:9–16.

Graham FF, Hales S, White PS, Baker MG. Review Global seroprevalence of legionellosis - a systematic review and meta-analysis. Scientific Reports 2020;10:1–11.

Gonçalves I, Simoes LC, Simoes M. Legionella pneumophila. Trends Microbiol 2021:S0966-842X(21)00113-X.-undefined.

Herwaldt LA, Marra AR. Legionella: A reemerging pathogen. Current Opinion in Infectious Diseases 2018;31:325–33.

Burstein D, Zusman T, Degtyar E, Viner R, Segal G, Pupko T. Legionella pneumophila 2009;5:31–2.

Doublet P, Khodr A, Kay E, Gomez-Valero L, Jarraud S, Buchrieser C, et al. Molecular epidemiology, phylogeny and evolution of Legionella. Infection, Genetics and Evolution 2016;43:108–22.

Felice A, Franchi M, de Martin S, Vitacolonna N, Iacumin L, Civilini M. Environmental surveillance and spatio-temporal analysis of Legionella spp. In a region of northeastern Italy (2002–2017). PLoS ONE 2019;14:1–23.

Cassell K, Davis JL, Berkelman R. Legionnaires’ disease in the time of COVID-19. Pneumonia 2021;13.

Palazzolo C, Maffongelli G, D’Abrano A, Lepore L, Mariano A, Vulcano A, et al. Legionella pneumonia: increased risk after COVID-19 lockdown? Italy, May to June 2020. Euro Surveill 2020;25:pii=2001372.

Rota MC, Caporali MG, Scaturro M, Girolamo A, Andrianou X, Ricci ML. Legionella pneumophila and SARS-COV-2 co-infection: The importance of laboratory diagnosis. Annali Dell’Istituto Superiore Di Sanita 2021;57:199–200.

Faccini M, Russo AG, Bonini M, Tunesi S, Murtas R, Sandrini M, et al. Large community-acquired Legionnaires’ disease outbreak caused by Legionella pneumophila serogroup 1, Italy, July to August 2018. Eurosurveillance 2020;25.

Napoli C, de Giglio O, Bertamino E, Montagna MT. Legionellosis in health care facilities: State of the art in control and prevention in Italy. Annali Di Igiene 2019;31:474–81.

Montagna MT, de Giglio O, Napoli C, Diella G, Rutigliano S, Agodi A, et al. Control and prevention measures for legionellosis in hospitals: A cross-sectional survey in Italy. Environmental Research 2018;166:55–60.

R Development Core Team. R a language and environment for statistical computing : reference index. R Foundation for Statistical Computing; 2010.

European Centre for Disease Prevention and Control. Legionnaires’ disease - Surveillance Atlas for Infectious Diseases. Stockholm: 2021.

Centro Nacional de Epidemiología Instituto de Salud Carlos III Ministerio de Ciencia Innovación. Resultados de la Vigilancia Epidemiológica de las enfermedades transmisibles. Informe anual. Años 2017-2018. Madrid: 2018.

European Centre for Disease Prevention and Control (ECDC). Guidelines for the implementation of non-pharmaceutical interventions against COVID-19 Key messages General considerations on NPI to control COVID-19. Stockholm: 2020.

Khodr A, Kay E, Gomez-Valero L, Ginevra C, Doublet P, Buchrieser C, et al. Molecular epidemiology, phylogeny and evolution of Legionella. Infection, Genetics and Evolution 2016;43:108–22.

Burillo A, Pedro-Botet ML, Bouza E. Microbiology and Epidemiology of Legionnaire’s Disease. Infectious Disease Clinics of North America 2017;31:7–27.

Riccò M, Peruzzi S, Ranzieri S, Giuri PG. Epidemiology of legionnaires’ disease in italy, 2004–2019: A summary of available evidence. Microorganisms 2021;9.

Keše D, Obreza A, Rojko T, Kišek TC. Legionella pneumophila—epidemiology and characterization of clinical isolates, Slovenia, 2006–2020. Diagnostics 2021;11.

Steffen R, Lautenschlager S, Fehr J. Travel restrictions and lockdown during the COVID-19 pandemic-impact on notified infectious diseases in Switzerland Running title: Impact of travel restrictions and lockdown on infectious diseases. 2020.

Ricketts KD, Joseph CA. The impact of new guidelines in Europe for the control and prevention of travel-associated Legionnaires’ disease. International Journal of Hygiene and Environmental Health 2006;209:547–52.

Mouchtouri VA, Rudge JW. Legionnaires’ Disease in Hotels and Passenger Ships: A Systematic Review of Evidence, Sources, and Contributing Factors. Journal of Travel Medicine 2015;22:325–37.

Núñez A, Sreeganga SD, Ramaprasad A. Access to healthcare during covid-19. International Journal of Environmental Research and Public Health 2021;18:1–12.

Czeisler MÉ, Marynak K, Clarke KEN, Salah Z, Shakya I, Thierry JM, et al. MMWR, Delay or Avoidance of Medical Care Because of COVID-19–Related Concerns — United States, June 2020. Morbidity and Mortality Weekly Report 2020;69:1250–7.

Verelst F, Kuylen E, Beutels P. Indications for healthcare surge capacity in European countries facing an exponential increase in coronavirus disease (COVID-19) cases, March 2020. Eurosurveillance 2020;25.

Statens Serum Institut - Denmark. Legionella 2020 Annual Report. Copenhagen: 2021.

Esterhuizen TM, Thabane L. Con: Meta-analysis: some key limitations and potential solutions. Nephrology Dialysis Transplantation 2016;31:882–5.

Imrey PB. Limitations of Meta-analyses of Studies with High Heterogeneity. JAMA Network Open 2020;3.

Principe L, Tomao P, Visca P. Legionellosis in the occupational setting. Environmental Research 2016:1–11.

Cunha BA, Burillo A, Bouza E. Legionnaires’ disease. The Lancet 2016;387:376–85.







How to Cite

Riccò M. Impact of lockdown and non-pharmaceutical interventions on the epidemiology of Legionnaires’ disease: Legionnaire’s disease and COVID-19. Acta Biomed [Internet]. 2022 Mar. 14 [cited 2024 Jul. 21];93(1):e2022090. Available from: