Legionnaires’ disease in Europe 2015.
Date: 2017-12-07
Institutions: European Centre for Disease Prevention and Control
Subjects: activity report, disease prevention, health control, infectious disease, public health

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SURVEILLANCE REPORT

Legionnaires’ disease in Europe 

2015

www.ecdc.europa.eu

ECDC SURVEILLANCE REPORT 

Legionnaires’ disease in Europe 

2015 

This report of the European Centre for Disease Prevention and Control (ECDC) was coordinated by Julien Beauté 
and Emmanuel Robesyn. 

Acknowledgements 
We would like to thank all ELDSNet members for their dedication in reporting national Legionnaires’ disease data 
and reviewing this report: 
Daniela Schmid, Günther Wewalka (Austria); Toon Braeye, Olivier Denis, Denis Piérard, Sophie Quoilin (Belgium); 
Lili Marinova, Iskra Tomova (Bulgaria); Ivan Radic, Aleksandar Simunovic, Ingrid Tripković (Croatia), Despo 
Pieridou, Ioanna Gregoriou, Maria Koliou (Cyprus); Vladimir Drašar, Irena Martinkova (Czech Republic); Charlotte 
Kjelsø, Søren Anker Uldum (Denmark); Irina Dontsenko, Rita Peetso (Estonia); Sari Jaakola; Jaana Kusnetsov; Outi 
Lyytikäinen; Silja Mentula (Finland); Christine Campese, Sophie Jarraud, Agnes Lepoutre (France); Bonita Brodhun, 
Christian Lück (Germany); Georgia Spala, Emanuel Velonakis (Greece); Ágnes Fehér, Ildikó Ferenczné Paluska 
(Hungary); Thorolfur Gudnason, Guðrún Sigmundsdóttir (Iceland); Mary Hickey, Tara Mitchell, Joan O’Donnell, 
Darina O'Flanagan (Ireland); Maria Grazia Caporali, Maria Luisa Ricci, Maria Cristina Rota (Italy); Antra Bormane, 
Jelena Galajeva, Oksana Savicka (Latvia); Migle Janulaitiene, Simona Zukauskaite-Sarapajeviene (Lithuania); Paul 
Reichert (Luxembourg); Jackie Maistre Melillo, Tanya Melillo Fenech, Graziella Zahra (Malta); Petra Brandsema, Ed 
IJzerman, Leslie Isken, Daan Notermans (Netherlands); Dominique Caugant, Heidi Lange, Joanne Michelle 
Fernandez Ocampo (Norway); Michal Czerwinski, Katarzyna Piekarska (Poland); Teresa Fernandes, Maria Teresa 
Marques (Portugal); Daniela Badescu, Gratiana Chicin (Romania); Danka Šimonyiová, Margita Špaleková (Slovak 
Republic); Eva Grilc, Maja Sočan, Darja Kese (Slovenia); Rosa Cano-Portero, Carmen Pelaz Antolin (Spain); 
Margareta Löfdahl (Sweden); Eleanor Anderson; Tim Harrison; Falguni Naik; Nick Phin; Kevin Pollock; Alison Potts; 
Elaine Stanford (United Kingdom), Cátia Cunha, Birgitta de Jong, Lara Payne Hallström, Teija Korhonen, Anna 
Renau-Rosell (ECDC). 

Suggested citation: European Centre for Disease Prevention and Control. Legionnaires’ disease in Europe, 2015. 
Stockholm: ECDC; 2017. 

Stockholm, June 2017 

ISBN 978-92-9498-071-7 

ISSN 2362-9835 

doi 10.2900/692621 

Catalogue number TQ-AR-17-001-EN-N 

© European Centre for Disease Prevention and Control, 2017 

Reproduction is authorised, provided the source is acknowledged 

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Legionnaires’ disease in Europe, 2015 

Contents 

Abbreviations ................................................................................................................................................ v 

Executive summary ........................................................................................................................................ 1 

1 Background ................................................................................................................................................ 2 

2 Methods ..................................................................................................................................................... 3 
2.1 The European Legionnaires’ Disease Surveillance Network ...................................................................... 3 
2.2 Data collection .................................................................................................................................... 3 
2.2.1 Legionnaires’ disease .................................................................................................................... 3 
2.2.2 Travel-associated Legionnaires’ disease .......................................................................................... 4 
2.2.3 Event-based surveillance ............................................................................................................... 4 
2.3 Data analysis ...................................................................................................................................... 4 
2.3.1 Legionnaires’ disease .................................................................................................................... 4 
2.3.2 Travel-associated Legionnaires’ disease .......................................................................................... 4 

3 Results ....................................................................................................................................................... 5 
3.1 Legionnaires’ disease ........................................................................................................................... 5 
3.1.1 Cases .......................................................................................................................................... 5 
3.1.3 Mortality .................................................................................................................................... 11 
3.1.4 Clinical and environmental microbiology ....................................................................................... 13 
3.2 Travel-associated Legionnaires’ disease ............................................................................................... 18 
3.2.1 Cases ........................................................................................................................................ 18 
3.2.2 Clinical microbiology ................................................................................................................... 21 
3.2.3 Travel: visits and sites ................................................................................................................ 22 
3.2.4 Clusters ..................................................................................................................................... 23 
3.2.5 Investigations and publication of accommodation sites .................................................................. 24 
3.3 Outbreaks (not travel-associated) ....................................................................................................... 24 

4 Discussion ................................................................................................................................................ 26 

5 Conclusion ................................................................................................................................................ 27 

References .................................................................................................................................................. 28 

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TECHNICAL REPORT 

Figures 

Figure 1. Notification rate of Legionnaires’ disease in the EU/EEA, by year of reporting, 1995–2015 ...................... 6 
Figure 2. Number of Legionnaires’ disease cases by month of reporting, EU/EEA, 2011–2015 ............................... 7 
Figure 3. Notifications of Legionnaires’ disease per 100 000 population, by reporting country, EU/EEA, 2015 ......... 8 
Figure 4. Notification rates of Legionnaires’ disease per 100 000, by sex and age group, EU/EEA, 2015 ................. 9 
Figure 5. Reported case–fatality ratio of Legionnaires’ disease by sex and age group, EU/EEA, 2015 ................... 12 
Figure 6. Distribution of sampling sites testing positive for Legionella, EU/EEA, 2015 ......................................... 17 
Figure 7. Distribution of sampling sites testing positive for Legionella and matching with clinical isolates, EU/EEA, 
2015 ........................................................................................................................................................... 17 
Figure 8. Number of travel-associated cases of Legionnaires’ disease reported to ELDSNet, 1987–2015 ............... 18 
Figure 9. Number of travel-associated cases of Legionnaires’ disease by month of disease onset, 2015 ............... 20 
Figure 10. Number of travel-associated cases of Legionnaires’ disease, by age group and sex, 2015 ................... 21 
Figure 11. Number of accommodation site visits and clusters of travel-associated cases of Legionnaires’ disease, by 
destination country, EU/EEA and neighbouring countries, 2015 ........................................................................ 22 
Figure 12. Number of accommodation site visits and clusters of travel-associated cases of Legionnaires’ disease, by 
destination country, worldwide, 2015 ............................................................................................................. 23 
Figure 13. Number of cases of travel-associated Legionnaires’ disease per cluster, 2015 .................................... 23 
Figure 14. Number of standard clusters of travel-associated Legionnaires’ disease per destination area (NUTS2), 
EU/EEA, 2015 .............................................................................................................................................. 24 

Tables 

Table 1. Completeness of reporting for Legionnaire’ disease cases, selected variables, EU/EEA, 2011–2015 .................... 5 
Table 2. Reported cases and notifications of Legionnaires’ disease per 100 000 population, by reporting country, 
EU/EEA, 2015 ...................................................................................................................................................... 8 
Table 3. Reported cases of Legionnaires’ disease, by country and setting of infection, EU/EEA, 2015a ........................... 10 
Table 4. Reported cases of Legionnaires’ disease by setting of infection and age group, EU/EEA, 2015 ......................... 10 
Table 5. Reported outcome of Legionnaires’ disease and case–fatality ratio by reporting country, EU/EEA, 2015 ........... 11 
Table 6. Reported case fatality of Legionnaires’ disease by setting, EU/EEA, 2015 ........................................................ 12 
Table 7. Adjusted predictors of fatal outcome of Legionnaires’ disease, EU/EEA, 2015 .................................................. 13 
Table 8. Reported laboratory methods and proportion of cases reported for each method, by reporting country, 
EU/EEA, 2015 .................................................................................................................................................... 14 
Table 9. Reported culture-confirmed cases of Legionnaires' disease and Legionella isolates, by species, EU/EEA, 2015 .. 14 
Table 10. Reported culture-confirmed cases of Legionnaires' disease and L. pneumophila isolates by serogroup, EU/EEA, 
2015 .......................................................................................................................................................................... 15 
Table 11. Reported monoclonal subtype for L. pneumophila serogroup 1 isolates, EU/EEA, 2015 .................................. 15 
Table 12. Environmental follow-up status of reported domestic cases of Legionnaires’ disease, by reporting country, 
EU/EEA, 2015 ............................................................................................................................................................. 16 
Table 13. Legionella findings of environmental investigations, by reporting country, EU/EEA, 2015 ............................... 16 
Table 14. Number of travel-associated cases of Legionnaires’ disease reported to ELDSNet, by reporting country, 
2010–2015 ........................................................................................................................................................ 18 
Table 15. Time to reporting (days between date of onset and reporting to ELDSNet), by reporting country, 2015 ......... 19 
Table 16. Reported diagnostic methods in travel-associated cases of Legionnaires’ disease, 2015 ................................. 21 
Table 17. Reported species or L. pneumophila serogroup in travel-associated cases of Legionnaires’ disease, 2015 ....... 22 

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Legionnaires’ disease in Europe, 2015 

Abbreviations 

CF 

CI 

EEA 

Case fatality 

Confidence interval 

European Economic Area 

ELDSNet 

European Legionnaires’ Disease Surveillance Network 

ESCMID 

European Society of Clinical Microbiology and Infectious Diseases 

ESGLI 

EU 

ESCMID study group for legionella infections 

European Union 

EWGLINET 

The European surveillance scheme for travel associated Legionnaires’ disease (2002–2010) 

IQR 

LD 

MAb 

NUTS 

PCR 

PR 

TALD 

TESSy 

UAT 

Interquartile range 

Legionnaires’ disease 

Monoclonal antibodies 

Nomenclature of territorial units for statistics 

Polymerase chain reaction 

Prevalence ratio 

Travel-associated Legionnaires’ disease 

The European Surveillance System 

Urinary antigen test 

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Legionnaires’ disease in Europe, 2015 

Executive summary 

This surveillance report is based on Legionnaires’ disease (LD) surveillance data collected for 2015. The 
surveillance is carried out by the European Legionnaires’ Disease Surveillance Network (ELDSNet) and coordinated 
by the European Centre for Disease Prevention and Control (ECDC) in Stockholm. Data were collected by appointed 
ELDSNet experts in each European country and electronically reported to The European Surveillance System 
(TESSy) database. 

The surveillance data are from two different schemes:  

 

 

Cases reported from European Union (EU) Member States, Iceland and Norway, with the following 
objectives: 
 
 
 
 

to monitor trends over time and to compare them across Member States 
to provide evidence-based data for public health decisions and actions at EU and/or Member State level 
to monitor and evaluate prevention and control programmes targeting LD at national and European level 
to identify population groups at risk and in need of targeted preventive measures. 

Reports of travel-associated cases of Legionnaires’ disease (TALD), including reports from countries outside 
the EU/EEA. This approach aims primarily at identifying clusters of cases that may otherwise not have been 
detected at the national level, thus enabling timely investigations and control measures at the implicated 
accommodation sites in order to prevent further infections. 

All notified cases 

For 2015, 7 034 cases of LD were reported by 28 EU Member States, plus Iceland and Norway. The number of 
notifications per 100 000 inhabitants was 1.37, which was the highest ever observed. Four countries (France, 
Germany, Italy, and Spain) accounted for 69% of cases. Notification rates ranged from 0.01 per 100 000 
inhabitants in Bulgaria to 5.14 per 100 000 in Slovenia. Most cases (69%) with known probable setting of infection 
were community-acquired, while 22% were travel-associated, and 8% were linked to healthcare facilities. Cases 
over 50 years of age accounted for 81% of all cases. The male-to-female ratio was 2.5. Case fatality was 8% in 
2015, comparable to previous years.  

Most cases (89%) were confirmed by urinary antigen test, and approximately 13% were culture-confirmed, but an 
increasing proportion of cases (10%) are reported to have been diagnosed by PCR. L. pneumophila serogroup 1 
was the most commonly identified pathogen, accounting for 81% of culture-confirmed cases. 

ECDC is giving priority to assisting countries with notification rates below one per million inhabitants to improve 
both diagnosis and reporting of LD.  

Travel-associated Legionnaires’ disease 

For 2015, 1 141 cases of TALD were reported by 22 EU/EEA countries and three other countries. This is lower than 
the total number of reported TALD cases because cases who stayed with relatives or friends are not reported 
under this scheme. The case numbers for 2015 were 20% higher than in 2014 (955 cases). Six countries (the 
United Kingdom, Italy, France, the Netherlands, Germany and Spain) reported three quarters of the cases. The 
1 141 TALD cases made a total of 1 606 international journeys, 1 221 (76%) of which were within the EU/EEA. 
Similar to previous years, there were twice as many male than female cases, and the median age was 62 years. 

A total of 155 standard clusters1 was detected, 17% more than in the previous year, which is in line with the 
overall increase in cases. Satisfactory control measures were implemented in a timely manner in all but eight 
notified clusters, with ELDSNet receiving feedback from a first risk assessment within two weeks and a final 
assessment within six weeks. The eight remaining accommodation site names were temporarily published on the 
ECDC website.  

Sixty percent of the clusters of travel-associated Legionnaires’ disease involved cases from different countries and 
would probably not have been detected without the international collaboration in ELDSNet. 

1 Clusters associated with only one accommodation site.  

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1 Background 

Legionnaires’ disease (LD) is a severe and sometimes fatal form of an infection with Legionella spp. These gram-
negative bacteria are found in freshwater and soil worldwide and tend to contaminate man-made water 
systems [1]. The disease was first described and named after a large outbreak among members of a US 
organisation of war veterans (American Legion) in the 1970s [2]. People are infected through inhalation of 
contaminated aerosols or aspiration of contaminated water. Person-to-person transmission has only been reported 
once [3]. LD is typically described as a severe pneumonia that may be accompanied by systemic symptoms such as 
fever, diarrhoea, myalgia, impaired renal and liver functions, and delirium. Known risk factors for LD include 
increasing age, being of male sex, smoking, chronic lung disease, diabetes, and various conditions associated with 
immunodeficiency [4]. In Europe, most cases (approximately 70%) are community-acquired and sporadic [5]. 
Studies suggest that the incidence of LD may be higher under certain environmental conditions such as warm and 
wet weather [6,7]. 

Legionnaires’ disease is notifiable in all EU and EEA countries, but is thought to be underreported for two main 
reasons. Firstly, it is underdiagnosed by clinicians who only rarely test patients for LD before empirically prescribing 
broad-spectrum antibiotics likely to cover Legionella spp. Secondly, some health professionals fail to notify cases to 
health authorities [1].  

The reported situation in Europe is heterogeneous, with a broad range of notification rates across countries 
reflecting both the quality of the national surveillance system and the local risk for LD. Some countries (e.g. France, 
Italy or the Netherlands) have already assessed their systems’ sensitivity, mainly through capture-recapture studies, 
and showed improvement over time [8–10]. For other countries such as Greece, a study using TALD notification 
and tourism denominator data strongly suggested substantial under-ascertainment [11]. In eastern and south-
eastern countries (e.g. Bulgaria, Poland or Romania), the numbers of cases reported have remained very low and 
are unlikely to reflect the true burden of LD [12,13]. Differences in laboratory practice may also partly explain 
these differences in notification rates [14]. 

Since 2010, the surveillance of LD in Europe has been operated by ELDSNet under the coordination of ECDC. Two 
distinct LD surveillance systems are currently in place. One is based on an annual reporting of all LD cases, the 
other on the daily reporting of TALD cases. Since some countries are unable to link the two reporting methods (i.e. 
TALD cases reported daily and those reported annually), it is not possible to merge the two databases. 

This is the seventh annual report presenting the analysis of disaggregated LD surveillance data in Europe and the 
sixth annual report covering both surveillance systems [14]. 

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Legionnaires’ disease in Europe, 2015 

2 Methods 

2.1 The European Legionnaires’ Disease Surveillance 
Network 

ELDSNet involves 28 EU Member States, plus Iceland and Norway. The network aims to identify relevant public 
health risks, enhance the prevention of cases through the detection of clusters, and monitor epidemiological trends. 
The latter objective provides the rationale for the annual collection, analysis and reporting of LD cases notified 
during the previous year. 

2.2 Data collection 

2.2.1 Legionnaires’ disease  

National data collected by appointed ELDSNet members in each country were electronically reported to the TESSy 
database, following a strict protocol. The deadline for 2015 data submission was 1 May 2016. Following data 
validation and cleaning, data for analysis were extracted on 8 February 2017. All LD cases in 2015 meeting the 
European case definition (see box below) were included.  

The EU case definition was amended in August 2012, and since then it has no longer been possible to report 
probable cases by only referring to an epidemiological link. TALD cases with a history of travelling abroad were 
reported by their country of residence. Cases are classified as travel-associated if they stayed at an 
accommodation site away from home during an incubation period of two to ten days prior to falling ill.  

EU case definition of Legionnaires’ disease [15] 

Clinical criteria 

Any person with pneumonia 

Laboratory criteria for case confirmation 

At least one of the following three: 

 
 
 

Isolation of Legionella spp. from respiratory secretions or any normally sterile site; 
Detection of Legionella pneumophila antigen in urine; 
Significant rise in specific antibody level to Legionella pneumophila serogroup 1 in paired serum samples. 

Laboratory criteria for a probable case 

At least one of the following four: 

 

 
 

 

Detection of Legionella pneumophila antigen in respiratory secretions or lung tissue e.g. by DFA staining 
using monoclonal-antibody-derived reagents; 
Detection of Legionella spp. nucleic acid in respiratory secretions, lung tissue or any normally sterile site; 
Significant rise in specific antibody level to Legionella pneumophila other than serogroup 1 or other 
Legionella spp. in paired serum samples; 
Single high level of specific antibody to Legionella pneumophila serogroup 1 in serum. 

Case classification 

Probable case: Any person meeting the clinical criteria AND at least one positive laboratory test for a probable 
case. 

Confirmed case: Any person meeting the clinical AND the laboratory criteria for case confirmation. 

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2.2.2 Travel-associated Legionnaires’ disease  

Individual cases of TALD are reported to ECDC on a daily basis via TESSy. The reporting country is generally the 
country where the case is diagnosed. Therefore, the reporting country can differ from the case’s country of 
residence. Case reports include age, sex, date of onset of disease, method of diagnosis and travel information for 
the places where the case had stayed from two to ten days prior to onset of disease. Only cases who stayed at a 
commercial (or public) accommodation site are reported (as opposed to cases of LD who stayed with relatives or 
friends). After receiving the report, each new case is classified as a single case or as part of a cluster, in 
accordance with the definitions agreed by the network: 

 

 

A single case: a person who stayed at a commercial accommodation site in the two to ten days before 
onset of disease; the site has not been associated with any other case of Legionnaires’ disease in the 
previous two years. 

A cluster: two or more cases who stayed at the same commercial accommodation site in the two to ten 
days before onset of disease, and whose dates of onset were within the same two-year period. 

If two or more clusters have at least one case in common, the combined cluster is notified as a ‘complex cluster’. 
A cluster of three cases or more, with onset of disease within a three-month period, is called a ‘rapidly evolving 
cluster’, and a summary report is sent to tour operators. When a cluster is detected, an investigation by public 
health authorities is required at the accommodation site. Preliminary results from such a risk assessment and the 
initiation of control measures should be reported back to ELDSNet by nationally appointed contact points within 
two weeks of the alert, using a preliminary form (Form A). A final form (Form B) is then used to report – within a 
further four weeks – the final results of environmental sampling and control measures. If the forms are not 
returned timely, or if they state that actions and control measures are unsatisfactory, ECDC publishes the name of 
the accommodation site associated with the cluster on its website and informs tour operators accordingly.  

2.2.3 Event-based surveillance 

ECDC identifies and monitors health threats through epidemic intelligence activities from a broad range of formal 
and informal sources on a daily basis. These threats, including outbreaks of Legionnaires’ disease, are documented 
and monitored through a dedicated database and a standard protocol. Experts evaluate and select threats that 
may require further attention by the nationally appointed contact points, depending on the potential impact these 
threats could have on the health of EU residents. More details on tools used for threat detection and threat 
communication can be found on an ECDC webpage dedicated to epidemic intelligence [16].  

In 2016, ELDSNet started a new data collection for outbreaks of non-travel associated Legionnaires’ disease. Data 
from the previous year are collected using a standardised questionnaire and submitted as an Excel spreadsheet. 
Data categories include the reporting country, the number of outbreaks, the size of the outbreaks, epidemiological 
and microbiological information of the investigation, and whether a vehicle or source was found.  

2.3 Data analysis 

2.3.1 Legionnaires’ disease  

Cases that were reported without specifying the laboratory method were excluded from the analysis. Since 
countries use diverse dates for national statistical purposes, TESSy collects the so-called ‘date used for statistics’ 
which can be the date of onset, diagnosis, or notification. Only cases with a 2015 date used for statistics were 
included in the analysis. Since environmental investigations are the responsibility of the Member States, we only 
analysed variables related to investigations of domestic cases. 

The distribution of cases and subsets with a fatal outcome were described by relevant independent variables. 
Continuous variables were summarised as medians with interquartile ranges (IQRs [Q1–Q3]) and compared across 
strata by using the Mann-Whitney U test. Prevalence ratios were calculated to test possible associations between 
categorical variables and are presented with their 95% confidence intervals, assuming a Poisson distribution. Age-
standardised rates were calculated using the direct method and the average age structure of the EU population for 
the period 2000–2010.  

2.3.2 Travel-associated Legionnaires’ disease  

We analysed the TALD data at the level of cases, travel visits and accommodation sites, and clusters. All reported 
cases with a date of onset in 2015 and their travel records were included in the analysis. For cases, we analysed 
epidemiological and diagnostic characteristics and described the temporal and geographic distribution. The number 
of travel visits and clusters were mapped at country level. The number of clusters within the EU/EEA was 
additionally mapped at level 2 of the nomenclature of territorial units for statistics (NUTS 2). 

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3 Results 

3.1 Legionnaires’ disease 

3.1.1 Cases 

Case validation and data completeness 
For 2015, 7 034 cases were reported by 30 countries.  

Overall, data completeness2 was stable between 2011 and 2015 (Table 1), with an increasing proportion of cases 
that were reported with a known outcome.  

Table 1. Completeness of reporting for Legionnaire’ disease cases, selected variables, EU/EEA,  
2011–2015 

Variable 

Date of onset (complete date) 

Outcome (not reported as unknown) 
Probable country of infection a (not missing) 

Place of residence (not missing or not reported at country level) 

Sequence type (not missing) 

Setting of infection (not missing or reported as unknown) 

Environmental investigation (not reported as unknown) 
Legionella found b (not missing or reported as unknown) 
Positive sampling site c (not missing or reported as unknown) 

2011 
% 

2012 
% 

2013 
% 

2014 
% 

2015 
% 

97.7 

69.9 

97.3 

47.5 

3.3 

90.8 

39.9 

92.1 

82.7 

98.3 

71.1 

93.7 

41.0 

4.1 

88.2 

49.2 

90.4 

77.9 

95.2 

76.8 

94.4 

49.5 

4.2 

88.8 

62.4 

97.6 

94.5 

94.8 

79.1 

91.6 

60.7 

4.4 

86.5 

67.9 

91.2 

99.9 

94.6 

80.2 

94.9 

55.1 

4.3 

87.4 

48.5 

95.1 

97.8 

a Completeness determined in cases reported to have been imported. 
b Completeness determined in cases reported to have prompted an environmental investigation. 
c Completeness determined in cases for which positive findings in an environmental investigation were reported. 

Case classification and notification rate 
Of the 7 034 notified cases, 6 570 (93.4%) were classified as confirmed and the remaining 464 (6.6%) as probable. 
Of 464 probable cases, 201 (43.3%) were reported by Germany. In 2015, the overall notification rate of 
Legionnaires’ disease was 1.37 per 100 000 population, which was the highest ever observed (Figure 1).  

2 Data completeness was calculated at time of analysis. Since reporting countries have the possibility to update their data, 
completeness for earlier years might differ from what was presented in previous reports.  

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Figure 1. Notification rate of Legionnaires’ disease in the EU/EEA*, by year of reporting, 1995–2015 

* EWGLINET member countries not belonging to the EU/EEA were excluded for 1995–2008. 

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Seasonality and geographical distribution 
Of the 6 960 cases that were reported with a timestamp for the month of reporting, 4 062 (58.4%) were reported 
between June and October. The number of cases increased over the 2011−2015 period (Figure 2). 

Figure 2. Number of Legionnaires’ disease cases by month of reporting, EU/EEA, 2011–2015 

Country-specific notification rates ranged from 0.01 cases per 100 000 inhabitants in Bulgaria to 5.14 per 100 000 
in Slovenia (Figure 3 and Table 2). The four largest reporting countries (France, Germany, Italy, and Spain) 
accounted for 69% of cases. Conversely, the 15 lowest reporting countries merely accounted for 3% of cases 
(Table 2). Age-standardised notification rates did not differ substantially from crude notification rates (Table 2).  

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Figure 3. Notifications of Legionnaires’ disease per 100 000 population, by reporting country, 
EU/EEA, 2015 

Table 2. Reported cases and notifications of Legionnaires’ disease per 100 000 population, by 
reporting country, EU/EEA, 2015 

Country 

Cases a 
(n) 

Population 
(n) 

Notification rate 
(n/100 000) 

Age-standardised 
notification rate 
(n/100 000) 

Average 
notification  
rate 
2010–14 
(n/100 000) 

Slovenia 

Denmark 

Italy 

Netherlands 

Spain 

France 

Austria 

Belgium 

Sweden 

Portugal 

Malta 

Norway 

106 

185 

1 553 

419 

1 024 

1 389 

160 

165 

142 

145 

6 

60 

2 062 874 

5 659 715 

60 795 612 

16 900 726 

46 449 565 

66 415 161 

8 576 261 

11 258 434 

9 747 355 

10 374 822 

429 344 

5 166 493 

Czech Republic 

120 

10 538 275 

Croatia 

Latvia 

Germany 

Luxembourg 

48 

22 

865 

5 

4 225 316 

1 986 096 

81 197 537 

562 958 

United Kingdom 

412 

64 875 165 

Hungary 

Estonia 

58 

6 

9 855 571 

1 313 271 

8 

5.14 

3.27 

2.55 

2.48 

2.21 

2.09 

1.87 

1.47 

1.46 

1.40 

1.40 

1.16 

1.14 

1.14 

1.11 

1.07 

0.89 

0.64 

0.59 

0.46 

4.98 

3.24 

2.23 

2.39 

2.12 

2.07 

1.79 

1.44 

1.42 

1.30 

1.38 

1.22 

1.10 

1.08 

1.09 

0.95 

0.91 

0.65 

0.56 

0.43 

3.57 

2.52 

2.26 

2.01 

1.86 

1.97 

1.40 

1.14 

1.32 

2.02 

1.38 

0.83 

0.78 

- 

1.89 

0.93 

1.04 

0.55 

0.38 

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Legionnaires’ disease in Europe, 2015 

Country 

Cases a 
(n) 

Population 
(n) 

Notification rate 
(n/100 000) 

Age-standardised 
notification rate 
(n/100 000) 

Average 
notification  
rate 
2010–14 
(n/100 000) 

Finland 

Iceland 

Greece 

Slovakia 

Lithuania 

Ireland 

Cyprus 

Poland 

Romania 

Bulgaria 

17 

1 

29 

14 

7 

11 

2 

23 

5 

1 

5 471 753 

329 100 

10 858 018 

5 421 349 

2 921 262 

4 628 949 

847 008 

38 005 614 

19 870 647 

7 202 198 

0.31 

0.30 

0.27 

0.26 

0.24 

0.24 

0.24 

0.06 

0.03 

0.01 

EU/EEA total 

7 000 

513 946 449 

1.37 

a Cases with known age and sex. 

0.27 

0.36 

0.25 

0.27 

0.25 

0.30 

0.25 

0.06 

0.03 

0.01 

1.31 

0.22 

0.62 

0.26 

0.17 

0.18 

0.24 

0.51 

0.04 

0.01 

0.01 

1.20 

Age and sex 
The median age at date of onset was 63 years (IQR 53–74). It was significantly higher in females (67 years, IQR 
55–78) than in males (62 years, IQR 52–73) (p<0.01). Notification rates increased with age, with a maximum of 
6.60 cases per 100 000 population in males aged 80 years and older (Figure 4). People older than 50 years of age 
accounted for 5 699 (81.4%) of 7 000 cases with known age and sex. Of the 7 000 cases with known age and sex, 
4 989 (71.3%) were male. In all age groups, LD was more common in males, with an overall male-to-female ratio 
of 2.5:1. The male-to-female ratio peaked at 3.4 in the age group of 40–49 years. 

Figure 4. Notification rates of Legionnaires’ disease per 100 000, by sex and age group, 
EU/EEA, 2015 

9 

 
 
 
 
 
 
 
 
 
 
 
Legionnaires’ disease in Europe, 2015 

SURVEILLANCE REPORT 

Settings 
Of 6 144 cases with reported setting of infection, 4 226 (68.8%) were reported as community-acquired (Table 3). 
In 2015, travel-related and healthcare-associated cases accounted for 21.7% and 7.7% of the total, respectively. 
The remaining cases (1.9%) were reported with other probable settings of infection. The distribution of cases by 
probable setting of infection has remained unchanged since 2008. Healthcare-associated cases represented a 
substantial proportion of cases in older age groups and in those under 20 years of age (Table 4).  

Table 3. Reported cases of Legionnaires’ disease, by country and setting of infection, EU/EEA, 2015a 

Community  Nosocomial 

Other 
healthcare 

Travel 
abroad 

Domestic 
travel 

Other 

Total 

Country 

n 

(%) 

Austria 
Belgium b 

Bulgaria 

Croatia 

Czech Republic 

Denmark 

Estonia 

Finland 

France 
Germany b 

Greece 
Hungary b 

Iceland 

Ireland 

Italy 

n 

7 

4 

0 

2 

6 

(%) 

(4.4) 

(7.1) 

(0.0) 

(4.2) 

(5.6) 

(8.0) 

(60.5) 

13 

(66.7) 

(37.5) 

1 

0 

(16.7) 

(0.0) 

115 

(71.9) 

29 

(51.8) 

(100) 

(93.8) 

(82.2) 

1 

45 

88 

98 

4 

6 

n 

1 

2 

0 

0 

0 

7 

0 

0 

(%) 

(0.6) 

(3.6) 

(0.0) 

(0.0) 

(0.0) 

(4.3) 

(0.0) 

(0.0) 

n 

34 

19 

0 

0 

5 

(%) 

(21.3) 

(33.9) 

(4.7) 

43 

(26.5) 

1 

(16.7) 

10 

(62.5) 

n 

3 

2 

0 

1 

6 

1 

0 

0 

(%) 

(1.9) 

(3.6) 

(0.0) 

(2.1) 

(5.6) 

(0.6) 

(0.0) 

(0.0) 

n 

0 

0 

0 

0 

2 

0 

0 

0 

(%) 

n 

(%) 

160 

(100) 

56 

(100) 

1 

(100) 

48 

(100) 

(1.9) 

107 

(100) 

162 

(100) 

6 

(100) 

16 

(100) 

820 

(59.2)  107 

(7.7) 

61 

(4.4) 

107 

(7.7) 

197 

(14.2) 

93 

(6.7)  1 385  (100) 

234 

(57.4) 

18 

19 

(65.5) 

1 

(4.4) 

(3.4) 

0 

0 

6 

18 

(81.8) 

0 

0 

(54.5) 

(1.7) 

107 

(26.2) 

42 

(10.3) 

6 

1 

1 

3 

(20.7) 

(4.5) 

(100) 

(27.3) 

2 

0 

0 

2 

(6.9) 

(0.0) 

(0.0) 

(18.2) 

0 

1 

3 

0 

0 

(0.0) 

408 

(100) 

(3.4) 

(13.6) 

29 

22 

1 

(100) 

(100) 

(100) 

11 

(100) 

1 221  (78.5) 

83 

25 

(1.6) 

178 

(11.4) 

12 

(0.8)  1 556  (100) 

Latvia 
Lithuania b 
Luxembourg b 

19 

(90.5) 

(33.3) 

1 

0 

Netherlands 

242 

(57.9) 

Norway 

Poland b 
Portugal b 

Slovakia 

Slovenia 

Spain 

23 

(38.3) 

2 

(28.6) 

9 

(64.3) 

103 

(97.2) 

916 

(89.5) 

United Kingdom 

150 

(36.4) 

0 

1 

0 

2 

0 

0 

2 

0 

34 

14 

75 

(68.8) 

11 

(10.1) 

0 

0 

2 

2 

1 

0 

(100) 

(0.7) 

147 

(35.2) 

24 

(0.0) 

(0.0) 

(5.5) 

(0.0) 

(0.0) 

(2.1) 

37 

(61.7) 

5 

9 

3 

3 

12 

(71.4) 

(8.3) 

(21.4) 

(2.8) 

(1.2) 

(0.2) 

205 

(49.8) 

0 

0 

8 

0 

0 

35 

42 

(9.5) 

(33.3) 

(0.0) 

(5.7) 

(0.0) 

(0.0) 

(7.3) 

(0.0) 

(0.0) 

(3.4) 

(10.2) 

0 

0 

0 

0 

0 

0 

0 

0 

0 

6 

0 

21 

(100) 

3 

2 

(100) 

(100) 

418 

(100) 

60 

(100) 

7 

(100) 

109 

(100) 

14 

(100) 

106 

(100) 

1 024  (100) 

412 

(100) 

7 

0 

0 

0 

0 

37 

0 

0 

0 

3 

0 

0 

6 

0 

0 

(5.3) 

(0.0) 

(33.3) 

(0.5) 

(14.3) 

(3.3) 

(3.4) 

21 

1 

(0.0) 

(0.0) 

(0.0) 

(0.0) 

(2.4) 

(0.0) 

(0.0) 

(0.0) 

Total 

4 226  (68.8)  324 

(5.3)  146 

(2.4)  785  (12.8)  546 

(8.9)  117 

(1.9)  6 144  (100) 

a Cyprus, Malta, Romania, and Sweden did not report setting of infection. 
b Country reported 50% or more cases without probable setting of infection. 

Table 4. Reported cases of Legionnaires’ disease by setting of infection and age group, EU/EEA, 2015 

Community  Nosocomial 

Other 
healthcare 

Travel 
abroad 

Domestic 
travel 

Other 

Total 

n 

16 

63 

(%) 

(66.7) 

(76.8) 

207 

(74.7) 

532 

(72.7) 

958 

(68.6) 

977 

(66.7) 

783 

(65.1) 

687 

(71.5) 

n 

6 

4 

3 

19 

49 

78 

92 

73 

(%) 

(25.0) 

(4.9) 

(1.1) 

(2.6) 

(3.5) 

(5.3) 

(7.6) 

(7.6) 

n 

0 

0 

3 

5 

7 

10 

30 

91 

(%) 

(1.1) 

(0.7) 

n 

2 

10 

26 

97 

(%) 

(8.3) 

(12.2) 

(9.4) 

(13.3) 

n 

0 

3 

28 

61 

(%) 

(3.7) 

(10.1) 

(8.3) 

(0.5) 

230 

(16.5)  112 

(8.0) 

(0.7) 

235 

(16.0)  147 

(10.0) 

(2.5) 

148 

(12.3)  134 

(11.1) 

(9.5) 

37 

(3.9) 

61 

(6.3) 

n 

0 

2 

10 

18 

41 

18 

16 

12 

(%) 

(2.4) 

n 

24 

82 

(%) 

(100) 

(100) 

(3.6) 

277 

(100) 

(2.5) 

732 

(100) 

(2.9)  1 397  (100) 

(1.2)  1 465  (100) 

(1.3)  1 203  (100) 

(1.2) 

961 

(100) 

4 223  (68.8)  324 

(5.3)  146 

(2.4)  785  (12.8)  546 

(8.9)  117 

(1.9)  6 141  (100) 

Country 

0-19 

20-29 

30-39 

40-49 

50-59 

60-69 

70-79 

≥80 

Total 

10 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
SURVEILLANCE REPORT 

Legionnaires’ disease in Europe, 2015 

Time to diagnosis 
Both date of onset and date of diagnosis were available in only 26.8% of cases (1 884/7 034). The median time 
from date of onset to diagnosis was five days (IQR 3–7), similar to previous years. 

3.1.3 Mortality 

Time and location 
The reported mortality rate of LD in 2015 was 0.09 cases per 100 000 inhabitants, which was consistent with the 
rates recorded since 2008, which have been hovering between 0.07 and 0.09 per 100 000. Of 5 642 cases with a 
known outcome, 456 were reported to have died, giving a case–fatality ratio (CFR) of 8.1%. In countries that 
reported less than 25% of cases with unknown outcome, the average CFR was 7.6% (Table 5). 

Table 5. Reported outcome of Legionnaires’ disease and case–fatality ratio by reporting country, 
EU/EEA, 2015 

Survival 

Death 

Unknown 

Total  Case fatality a 

Country 

Ireland 

Poland 

Malta 

Czech Republic 

Hungary 

Sweden 

Denmark 

Spain 

France 

United Kingdom 

Slovenia 

Germany 

Portugal 

Latvia 

Greece 

Austria 

Netherlands 

Croatia 

Bulgaria 

Cyprus 

Estonia 

Iceland 

Romania 

Slovakia 

Belgium 

Finland 

Italy 

Lithuania 

Luxembourg 

Norway 

n 

8 

19 

5 

102 

50 

124 

164 

709 

1 182 

387 

100 

780 

132 

21 

25 

154 

405 

47 

1 

2 

6 

1 

5 

14 

74 

0 

621 

4 

3 

41 

Subtotal 
EU/EEA total c 

5 186 

4 443 

(%) 

(72.7) 

(82.6) 

(83.3) 

(85.0) 

(86.2) 

(87.3) 

(88.6) 

(69.2) 

(85.1) 

(93.9) 

(94.3) 

(90.2) 

(91.0) 

(95.5) 

(86.2) 

(96.3) 

(96.7) 

(97.9) 

(100) 

(100) 

(100) 

(100) 

(100) 

(100) 

(37.8) 

(0.0) 

(39.9) 

(57.1) 

(60.0) 

(68.3) 

(73.7) 

(85.6) 

n 

3 

4 

1 

18 

8 

18 

21 

72 

117 

25 

6 

44 

7 

1 

1 

6 

13 

1 

0 

0 

0 

0 

0 

0 

5 

0 

80 

1 

0 

4 

456 

366 

(%) 

(27.3) 

(17.4) 

(16.7) 

(15.0) 

(13.8) 

(12.7) 

(11.4) 

(7.0) 

(8.4) 

(6.1) 

(5.7) 

(5.1) 

(4.8) 

(4.5) 

(3.4) 

(3.8) 

(3.1) 

(2.1) 

(0.0) 

(0.0) 

(0.0) 

(0.0) 

(0.0) 

(0.0) 

(2.6) 

(0.0) 

(5.1) 

(14.3) 

(0.0) 

(6.7) 

(6.5) 

(7.0) 

n 

0 

0 

0 

0 

0 

0 

0 

243 

90 

0 

0 

41 

6 

0 

3 

0 

1 

0 

0 

0 

0 

0 

0 

0 

117 

17 

855 

2 

2 

15 

1 392 

384 

(%) 

(0.0) 

(0.0) 

(0.0) 

(0.0) 

(0.0) 

(0.0) 

(0.0) 

(23.7) 

(6.5) 

(0.0) 

(0.0) 

(4.7) 

(4.1) 

(0.0) 

(10.3) 

(0.0) 

(0.2) 

(0.0) 

(0.0) 

(0.0) 

(0.0) 

(0.0) 

(0.0) 

(0.0) 

(59.7) 

(100) 

(54.9) 

(28.6) 

(40.0) 

(25.0) 

(19.8) 

(7.4) 

n 

11 

23 

6 

120 

58 

142 

185 

1 024 

1 389 

412 

106 

865 

145 

22 

29 

160 

419 

48 

1 

2 

6 

1 

5 

14 

196 

17 

1 556 

7 

5 

60 

7 034 

5 193 

% 

27.3 

17.4 

16.7 

15.0 

13.8 

12.7 

11.4 

9.2 

9.0 

6.1 

5.7 

5.3 

5.0 

4.5 

3.8 

3.8 

3.1 

2.1 

0.0 

0.0 

0.0 

0.0 

0.0 

0.0 
NA b 

NA 

NA 

NA 

NA 

NA 

8.1 

7.6 

a Denominator: cases with known outcome (survivals and deaths) 
b Not applicable if ≥25% of outcomes unknown 
c Includes only countries where <25% of outcomes unknown 

11 

 
 
 
 
 
 
 
 
 
 
Legionnaires’ disease in Europe, 2015 

SURVEILLANCE REPORT 

Age and sex 
Case–fatality ratio was higher for older age groups in males and females (Figure 5). In people over 50 years of 
age, the CFR increased with age, showing a similar pattern in males and females. In older age groups, the CFR 
was slightly higher in males than females. 

Figure 5. Reported case–fatality ratio of Legionnaires’ disease by sex and age group, EU/EEA, 2015 

Settings  
The CFR was almost four times higher in healthcare-associated cases (nosocomial and other healthcare) than in 
community-acquired cases (Table 6). This is not surprising since healthcare-associated cases are probably more 
likely to have underlying conditions. Cases with a history of travel abroad had the lowest CFR. This could be due to 
a healthy traveller effect. 

Table 6. Reported case fatality of Legionnaires’ disease by setting, EU/EEA, 2015 

Setting 

Other healthcare 

Nosocomial 

Community 

Domestic travel 

Travel abroad 

Other 

Total 

Deaths 
n 

35 

76 

238 

27 

17 

3 

396 

Total 
n 

122 

271 

3 245 

412 

739 

104 

4 893 

CF 
% 

28.7 

28.0 

7.3 

6.6 

2.3 

2.9 

8.1 

Adjusted predictors for fatal outcome 
In a multivariable analysis adjusted for age and sex, healthcare-associated cases were significantly associated with 
a higher risk for fatal outcome (Table 7). Both being female and a history of travel abroad were protective. 

12 

 
 
 
 
 
 
 
 
 
 
 
SURVEILLANCE REPORT 

Legionnaires’ disease in Europe, 2015 

Table 7. Adjusted predictors of fatal outcome of Legionnaires’ disease, EU/EEA, 2015 (n=4 879) 

Risk factor 

Age 

Sex 

Female 

Male 

Odds 
ratio 

95%CI 

P-value 

Cases 
exposed 
% 

1.05 

1.04-1.06 

<0.01 

100 

1 (ref.) 

1.40 

1.10-1.79 

0.01 

Probable setting of infection  

Community 

Nosocomial 

Other healthcare 

Travel abroad 

Domestic travel 

Other 

1 (ref.) 

4.37 

2.67 

0.36 

0.88 

0.47 

3.21-5.96 

<0.01 

1.72-4.15 

<0.01 

0.22-0.59 

<0.01 

15.0 

0.58-1.34 

0.15-1.51 

0.56 

0.21 

8.5 

2.1 

28.9 

71.1 

66.4 

5.6 

2.5 

3.1.4 Clinical and environmental microbiology 

Laboratory methods 
For the 7 034 cases reported, 8 052 laboratory tests were performed, 6 234 (77.4%) of which were urinary antigen 
detections. Of the 30 countries reporting cases, 11 reported more than one test per case, with an average of 1.3 
tests per case. The distribution of tests varied greatly across countries (Table 8).  

Culture confirmations were not reported by 13 countries, but accounted for 41.1% of diagnoses in Denmark and 
83.3% in Estonia. Of the countries not reporting any culture confirmations in 2015, seven (Bulgaria, Croatia, 
Cyprus, Latvia, Lithuania, Malta, Romania) have never reported any culture confirmation. Some large reporting 
countries such as Italy or Spain relied almost exclusively on urinary antigen tests (UAT). Of 7 034 cases, 6 234 
(88.6%) were UAT-positive, a proportion similar to 2014. Over the past five years, the proportion of PCR-
diagnosed cases continuously increased from below 2.5% in 2010 to 10.5% in 2015. In 2015, the proportion of 
PCR-ascertained cases was at least 20% in five countries (the Czech Republic, Denmark, Luxembourg, Sweden, 
and the UK). In Denmark, this proportion was above 75%. 

13 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
Legionnaires’ disease in Europe, 2015 

SURVEILLANCE REPORT 

Table 8. Reported laboratory methods and proportion of cases reported for each method, by 
reporting country, EU/EEA, 2015  

Country 

Urinary 
antigen 

Culture 

Laboratory test method* 
Single high 
titre 

PCR 

Fourfold 
titre rise 

Direct immune-
fluorescence 

Total 
tests 

Total 
cases 

(%) 

n 

(%) 

n 

(%) 

Austria 

Belgium 

Bulgaria 

Croatia 

Cyprus 

n 

(%) 

n 

(%) 

122 

(76.3)  30 

(18.8) 

n 

5 

(%) 

(3.1) 

165 

(84.2) 

1 

48 

2 

(100) 

(100) 

(100) 

7 

0 

0 

0 

(3.6) 

21 

(10.7) 

0 

0 

0 

Czech Republic 

104 

(86.7)  28 

(23.3)  41 

(34.2) 

n 

3 

1 

0 

0 

0 

3 

(1.9) 

(0.5) 

(2.5) 

Denmark 

93 

(50.3)  76 

(41.1)  139  (75.1)  10 

(5.4) 

1 

(16.7) 

16 

(94.1) 

5 

0 

(83.3) 

0 

1 

(5.9) 

1 324  (95.3)  345  (24.8)  125 

(9.0) 

0 

0 

4 

(0.3) 

598 

(69.1)  64 

(7.4)  139  (16.1)  51 

(5.9) 

13 

(1.5) 

Estonia 

Finland 

France 

Germany 

Greece 

Hungary 

Iceland 

Ireland 

Italy 

Latvia 

Lithuania 

Luxembourg 

Malta 

Norway 

Poland 

Portugal 

Romania 

Slovakia 

Slovenia 

Spain 

Sweden 

(10.3) 

(5.2) 

27 

43 

1 

(93.1) 

(74.1) 

(100) 

10 

(90.9) 

3 

3 

0 

0 

1 494  (96.0)  35 

(2.2) 

18 

(81.8) 

5 

4 

6 

(71.4) 

(80.0) 

(100) 

0 

0 

0 

0 

0 

4 

0 

2 

2 

0 

0 

1 

0 

49 

16 

(81.7) 

(69.6) 

2 

0 

(3.3) 

(0.0) 

126 

(86.9)  18 

(12.4) 

5 

14 

79 

(100) 

(100) 

0 

0 

(74.5)  26 

(24.5) 

995 

(97.2)  59 

(5.8) 

9 

3 

0 

0 

0 

1 

1 

(15.0) 

(13.0) 

(0.9) 

(0.1) 

3 

(10.3) 

(6.9) 

14 

(24.1) 

0 

0 

(18.2) 

(0.1) 

18 

(1.2) 

(20.0) 

(18.2) 

(28.6) 

(0.0) 

(21.7) 

4 

2 

0 

0 

0 

0 

5 

0 

0 

0 

0 

7 

Netherlands 

381 

(90.9)  79 

(18.9)  65 

(15.5) 

0 

2 

0 

0 

0 

0 

1 

0 

0 

4 

(1.0) 

(0.5) 

(0.3) 

(1.7) 

(0.4) 

(1.4) 

(0.7) 

0 

1 

0 

0 

6 

0 

0 

0 

0 

6 

0 

0 

1 

0 

0 

0 

0 

3 

(0.7) 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

0 

1 

0 

0 

0 

0 

1 

0 

0 

0 

0 

0 

0 

0 

0 

0 

n 

160 

196 

1 

48 

2 

176 

319 

6 

17 

n 

160 

196 

1 

48 

2 

120 

185 

6 

17 

1 802  1 389 

865 

865 

33 

65 

1 

12 

29 

58 

1 

11 

(0.1) 

1 556  1 556 

22 

22 

7 

5 

6 

7 

5 

6 

(0.2) 

532 

419 

60 

24 

60 

23 

145 

145 

5 

14 

5 

14 

106 

106 

1 075  1 024 

194 

598 

142 

412 

101 

(71.1)  18 

(12.7)  61 

(43.0)  14 

(9.9) 

United Kingdom 

386 

(93.7)  92 

(22.3)  117  (28.4) 

0 

(0.0) 

(0.7) 

13 

(1.3) 

Total 

6 234  (88.6)  890  (12.7)  737  (10.5)  139  (2.0)  50 

(0.7) 

2 

(0.0)  8 052  7 034 

* More than one method per case possible 

Pathogens 
Of 890 culture-confirmed cases, 855 (96.1%) were due to L. pneumophila (Table 9). Serogroup 1 accounted for 
732 (85.6%) of 855 culture-confirmed cases with L. pneumophila ( 

Table 10). Four subtypes (Allentown/France, Benidorm, Knoxville and Philadelphia) accounted for 78.8% of the 
170 L. pneumophila serogroup 1 isolates that were subtyped using monoclonal antibodies (MAb) (Table 11). In 
addition, three L. pneumophila serogroup 5 isolates were of Cambridge subtype and one L. pneumophila serogroup 
4 isolate was of Portland subtype. 

Table 9. Reported culture-confirmed cases of Legionnaires' disease and Legionella isolates, by 
species, EU/EEA, 2015 

Species 

L. anisa 

L. bozemanii 

L. longbeachae 

Culture-confirmed cases 

n 

1 

2 

7 

(%) 

(0.1) 

(0.2) 

(0.8) 

14 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
SURVEILLANCE REPORT 

Legionnaires’ disease in Europe, 2015 

Species 

L. pneumophila 

L. other species 

L. species unknown 

Total 

Culture-confirmed cases 

n 

855 

13 

12 

890 

(%) 

(96.1) 

(1.5) 

(1.3) 

(100) 

Table 10. Reported culture-confirmed cases of Legionnaires' disease and L. pneumophila isolates by 
serogroup, EU/EEA, 2015 

Serogroup 

1 

2 

3 

4 

5 

6 

7 

8 

10 

12 

14 

15 

L. pneumophila non serogroup 1 

L. pneumophila serogroup mixed 

L. pneumophila SG unknown 

Total 

Culture-confirmed cases  
with L. pneumophila 

n 

732 

3 

18 

7 

5 

11 

3 

1 

4 

1 

1 

5 

5 

5 

54 

855 

(%) 

(85.6) 

(0.4) 

(2.1) 

(0.8) 

(0.6) 

(1.3) 

(0.4) 

(0.1) 

(0.5) 

(0.1) 

(0.1) 

(0.6) 

(0.6) 

(0.6) 

(6.3) 

(100) 

Table 11. Reported monoclonal subtype for L. pneumophila serogroup 1 isolates, EU/EEA, 2015 

Monoclonal subtype 

Philadelphia 

Allentown 

Allentown/France 

Benidorm 

France 

Knoxville 
Subtotal MAb 3/1 positive a 

OLDA 

Oxford 

OLDA/Oxford 

Bellingham 

Subtotal MAb 3/1 negative 

n 

41 

1 

21 

29 

1 

43 

(%) 

(24.1) 

(0.6) 

(12.4) 

(17.1) 

(0.6) 

(25.3) 

136 

(80.0) 

7 

1 

18 

8 

34 

(4.1) 

(0.6) 

(10.6) 

(4.7) 

(20.0) 

Total 

170 

(100) 

a Monoclonal types are grouped by the presence (or lack) of the virulence-associated epitope recognised by the MAb 3/1 
(Dresden Panel). 

Environment 
Environmental investigation status was available for 2 601 (48.5%) of 5 359 cases known to not have travelled 
abroad within the incubation period (Table 12). An investigation was carried out in 910 (35.0%) of these 2 601 
cases with known status. Legionella was detected in 430 (49.5%) of 868 investigations for which environmental 
findings were reported (Table 13), with 456 sampling sites testing positive: 411 samples from water systems (77 
hot water systems, 26 cold water systems and 308 non-specified water systems), 22 cooling towers, 13 pools and 
10 sampling sites reported as ‘other’ (Figure 6). In 42 (9.8%) of the 430 cases with positive environmental 

15 

 
 
 
 
 
 
 
 
 
 
 
 
Legionnaires’ disease in Europe, 2015 

SURVEILLANCE REPORT 

findings, isolates could be matched to clinical isolates: 34 from water systems, four pools, two cooling towers, one 
site reported as ‘other’ and one unknown (Figure 7).  

Table 12. Environmental follow-up status of reported domestic cases of Legionnaires’ disease, by 
reporting country, EU/EEA, 2015* 

Country 

Austria 

Belgium 

Bulgaria 

Croatia 

Cases without 
investigation 
n 

(%) 

7 

0 

1 

0 

(5.6) 

(100) 

Czech Republic 

13 

(12.7) 

Denmark 

Estonia 

Finland 

France 

Germany 

Greece 

Hungary 

Ireland 

Italy 

Latvia 

Lithuania 

Netherlands 

Norway 

Poland 

Portugal 

Slovakia 

Slovenia 

Spain 

United Kingdom 

Total 

0 

5 

0 

0 

0 

20 

3 

2 

1 110 

2 

0 

(100) 

(87.0) 

(14.3) 

(25.0) 

(72.5) 

(9.5) 

223 

(82.3) 

0 

0 

50 

8 

103 

0 

144 

1 691 

(50.0) 

(72.7) 

(100) 

(0.0) 

(69.6) 

(31.6) 

Cases with investigation 

Status unknown 

Total 

n 

117 

0 

0 

0 

89 

24 

0 

0 

0 

0 

3 

18 

5 

421 

19 

3 

39 

19 

2 

48 

3 

0 

37 

63 

910 

(%) 

(92.9) 

(87.3) 

(20.2) 

(13.0) 

(85.7) 

(62.5) 

(27.5) 

(90.5) 

(100) 

(14.4) 

(82.6) 

(100) 

(48.0) 

(27.3) 

(3.7) 

(30.4) 

(17.0) 

n 

2 

37 

0 

48 

0 

95 

0 

6 

1 278 

301 

0 

0 

1 

0 

0 

0 

9 

4 

0 

2 

0 

0 

975 

0 

(%) 

(1.6) 

(100) 

(100) 

(79.8) 

(100) 

(100) 

(100) 

(12.5) 

(3.3) 

(17.4) 

(2.0) 

(96.3) 

2 758 

(51.5) 

n 

126 

37 

1 

48 

102 

119 

5 

6 

1 278 

301 

23 

21 

8 

1 531 

21 

3 

271 

23 

2 

100 

11 

103 

1 012 

207 

5 359 

* Cases with settings reported as ‘unknown’ or ‘travel abroad’ were not included 

Table 13. Legionella findings of environmental investigations, by reporting country, EU/EEA, 2015* 

Legionella detected 

Legionella not detected 

Result unknown 

Total 

n 

48 

51 

19 

2 

18 

1 

167 

14 

3 

21 

0 

2 

26 

(%) 

(41.0) 

(57.3) 

(79.2) 

(66.7) 

(100) 

(20.0) 

(39.7) 

(73.7) 

(100) 

(53.8) 

(100) 

(54.2) 

n 

69 

38 

5 

1 

0 

4 

251 

5 

0 

17 

0 

0 

21 

(%) 

(59.0) 

(42.7) 

(20.8) 

(33.3) 

(80.0) 

(59.6) 

(26.3) 

(43.6) 

(43.8) 

n 

0 

0 

0 

0 

0 

0 

3 

0 

0 

1 

19 

0 

1 

(%) 

n 

117 

89 

24 

3 

18 

5 

(0.7) 

421 

19 

3 

39 

19 

2 

48 

(2.6) 

(100) 

(2.1) 

Country 

Austria 

Czech Republic 

Denmark 

Greece 

Hungary 

Ireland 

Italy 

Latvia 

Lithuania 

Netherlands 

Norway 

Poland 

Portugal 

16 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
SURVEILLANCE REPORT 

Legionnaires’ disease in Europe, 2015 

Slovakia 

Spain 

United Kingdom 

Total 

2 

25 

31 

430 

(66.7) 

(67.6) 

(49.2) 

(47.3) 

1 

0 

26 

438 

(33.3) 

(0.0) 

(41.3) 

(48.1) 

0 

12 

6 

42 

(32.4) 

(9.5) 

(4.6) 

3 

37 

63 

910 

* Cases with settings reported as ‘unknown’ or ‘travel abroad’ were not included 

Figure 6. Distribution of sampling sites testing positive for Legionella, EU/EEA, 2015 

Figure 7. Distribution of sampling sites testing positive for Legionella and matching with clinical 
isolates, EU/EEA, 2015 

17 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
Legionnaires’ disease in Europe, 2015 

SURVEILLANCE REPORT 

3.2 Travel-associated Legionnaires’ disease 

3.2.1 Cases 

Notifications 
ELDSNet received reports of 1 141 cases of TALD with date of onset in 2015, 20% more cases than in 2014, and 
the highest annual number of TALD cases ever reported to the network (Figure 8). 

Figure 8. Number of travel-associated cases of Legionnaires’ disease reported to ELDSNet, 1987–
2015 

Cases were reported from 25 countries: 22 EU/EEA Member States and three non-EU/EEA countries: Switzerland 
(30 cases), the USA (6 cases), and Australia (2 cases). Two-thirds (66.2%) of all TALD cases were reported by only 
four countries (in decreasing order of frequency): the United Kingdom, Italy, France, and the Netherlands (Table 
14).  

The median time from date of onset to ELDSNet reporting was 17 days, ranging from 10 days (France) to 42 days 
(Germany) (Table 15). 

Table 14. Number of travel-associated cases of Legionnaires’ disease reported to ELDSNet, by 
reporting country, 2010–2015 

2010 

2011 

Number of reported cases 

2012 

2013 

2014 

2015 

n 
154 
142 
191 
148 
0 
67 
20 
25 
32 
16 
0 
19 
3 

(%) 
(17.8) 
(16.4) 
(22.1) 
(17.1) 

(7.8) 
(2.3) 
(2.9) 
(3.7) 
(1.9) 

(2.2) 

n 
116 
154 
162 
120 
0 
67 
28 
18 
32 
11 
0 
25 
0 

(%) 
(15.2) 
(20.2) 
(21.2) 
(15.7) 

(8.8) 
(3.7) 
(2.4) 
(4.2) 
(1.4) 

(3.3) 

n 
135 
156 
170 
113 
1 
68 
49 
13 
41 
19 
0 
27 
2 

(%) 
(16.2) 
(18.8) 
(20.5) 
(13.6) 
(0.1) 
(8.2) 
(5.9) 
(1.6) 
(4.9) 
(2.3) 

(3.2) 
(0.2) 

n 
115 
141 
161 
109 
34 
55 
24 
20 
25 
25 
0 
23 
0 

(%) 
(14.6) 
(17.9) 
(20.5) 
(13.9) 
(4.3) 
(7.0) 
(3.0) 
(2.5) 
(3.2) 
(3.2) 

(2.9) 

n 
160 
151 
186 
132 
54 
55 
51 
25 
37 
12 
10 
36 
7 

(%) 
(16.8) 
(15.8) 
(19.5) 
(13.9) 
(5.7) 
(5.8) 
(5.4) 
(2.6) 
(3.9) 
(1.3) 
(1.0) 
(3.8) 
(0.7) 

n 
213 
202 
200 
142 
76 
51 
38 
36 
32 
31 
30 
28 
14 

(%) 
(18.7) 
(17.7) 
(17.5) 
(12.4) 
(6.7) 
(4.5) 
(3.3) 
(3.2) 
(2.8) 
(2.7) 
(2.6) 
(2.5) 
(1.2) 

Reporting 
country 

United Kingdom 
Italy 
France 
Netherlands 
Germany 
Spain 
Sweden 
Norway 
Denmark 
Belgium 
Switzerland 
Austria 
Portugal 

18 

 
 
 
 
 
 
 
 
 
 
 
  
  
  
  
  
  
  
  
  
SURVEILLANCE REPORT 

Legionnaires’ disease in Europe, 2015 

Reporting 
country 

Czech Republic 
Finland 
United States of 
America 
Slovenia 
Ireland 
Greece 
Luxembourg 
Australia 
Latvia 
Bulgaria 
Lithuania 
Romania 
Israel 
Malta 
Turkey 
Thailand 
Andorra 
New Zealand 
Canada 
Cyprus 
Hungary 
Croatia 
Others 
Total 

2010 

2011 

Number of reported cases 

2012 

2013 

2014 

2015 

n 
5 
8 

11 

1 
7 
0 
3 
0 
1 
0 
0 
0 
0 
5 
0 
0 
0 
0 
0 
0 
2 
2 
2 
864 

(%) 
(0.6) 
(0.9) 

(1.3) 

(0.1) 
(0.8) 

(0.1) 

(0.6) 

(0.2) 

(1.2) 
(100) 

n 
7 
5 

5 

1 
4 
4 
0 
0 
1 
0 
0 
0 
0 
1 
0 
0 
0 
0 
0 
0 
2 
0 
0 
763 

(%) 
(0.9) 
(0.7) 

(0.7) 

(0.1) 
(0.5) 
(0.5) 

(0.1) 

(0.1) 

(0.3) 

(100) 

n 
5 
6 

6 

2 
7 
1 
1 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
1 
4 
4 
0 
831 

(%) 
(0.6) 
(0.7) 

(0.7) 

(0.2) 
(0.8) 
(0.1) 
(0.1) 

(0.1) 
(0.5) 
(0.5) 

(100) 

n 
5 
9 

9 

5 
8 
8 
1 
0 
1 
0 
0 
0 
1 
1 
3 
1 
0 
0 
2 
1 
0 
0 
0 
787 

(%) 
(0.6) 
(1.1) 

(1.1) 

(0.6) 
(1.0) 
(1.0) 
(0.1) 

(0.1) 

(0.1) 
(0.1) 
(0.4) 
(0.1) 

(0.3) 
(0.1) 

(100) 

n 
14 
2 

3 

3 
1 
4 
0 
0 
0 
0 
0 
0 
4 
2 
1 
1 
1 
1 
0 
0 
0 
0 
0 
953 

(%) 
(1.5) 
(0.2) 

(0.3) 

(0.3) 
(0.1) 
(0.4) 

(0.4) 
(0.2) 
(0.1) 
(0.1) 
(0.1) 
(0.1) 

(100) 

n 
11 
9 

6 

5 
5 
4 
2 
2 
1 
1 
1 
1 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
1 141 

(%) 
(1.0) 
(0.8) 

(0.5) 

(0.4) 
(0.4) 
(0.4) 
(0.2) 
(0.2) 
(0.1) 
(0.1) 
(0.1) 
(0.1) 

(100) 

a The reporting country is generally the country where the case is diagnosed. The reporting country is not necessarily identical 
with the country of residence. 

Table 15. Time to reporting (days between date of onset and reporting to ELDSNet), by reporting 
country, 2015 

Reporting country 

Number of cases 

Mean 

Median 

25th quantile 

75th quantile 

Time to reporting (days) 

France 

Greece 

Norway 

Austria 

Romania 

Ireland 

Netherlands 

Slovenia 

United Kingdom 

Latvia 

United States of America 

Belgium 

Finland 

Lithuania 

Switzerland 

Bulgaria 

Luxembourg 

Denmark 

Italy 

Sweden 

Australia 

Spain 

Czech Republic 

Portugal 

Germany 

Total  

200 

4 

36 

28 

1 

5 

142 

5 

213 

1 

6 

31 

9 

1 

30 

1 

2 

32 

202 

38 

2 

51 

11 

14 

76 

1 141 

15 

22 

17 

15 

13 

19 

22 

18 

23 

15 

28 

24 

33 

22 

32 

25 

25 

45 

57 

31 

35 

45 

79 

51 

49 

30 

10 

11 

11 

13 

13 

14 

14 

14 

14 

15 

16 

18 

20 

22 

22 

25 

25 

29 

30 

30 

35 

35 

38 

41 

42 

22 

8 

10 

8 

8 

13 

8 

10 

14 

10 

15 

14 

12 

14 

22 

15 

25 

16 

20 

16 

19 

26 

16 

36 

24 

24 

16 

15 

23 

16 

20 

13 

22 

22 

22 

22 

15 

29 

26 

41 

22 

40 

25 

34 

42 

65 

43 

44 

53 

104 

80 

62 

36 

The reported TALD cases came from a total of 36 countries. The majority of cases resided in those countries that 
reported the most cases, but according to ELDSNet data, 52 (4.6 %) cases were non-EU/EEA residents who came 
from Switzerland (29), the USA (6), Australia (5), Canada (2), China (2), New Caledonia (2), Argentina (1), Brazil 
(1), Guernsey (1), Guinea-Bissau (1), Israel (1), and Sri Lanka (1). 

19 

 
 
 
 
 
 
 
 
 
 
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
  
Legionnaires’ disease in Europe, 2015 

SURVEILLANCE REPORT 

Seasonality 
In 2015, two thirds of the cases fell ill between June and October, which is in line with the known seasonality of 
Legionnaires' disease (Figure 9). 

Figure 9. Number of travel-associated cases of Legionnaires’ disease by month of disease onset, 2015  

Age and sex 
Similar to previous years and the overall distribution of Legionnaires' disease, over two thirds (69%) of the 
reported TALD cases were male. Cases had a median age of 62 (IQR 53-71); 82% of cases occurred in people 50 
years and older (Figure 10). 

20 

 
 
 
 
 
 
 
 
 
 
 
SURVEILLANCE REPORT 

Legionnaires’ disease in Europe, 2015 

Figure 10. Number of travel-associated cases of Legionnaires’ disease, by age group and sex, 2015 

Outcome 
Outcome was provided for 611 (54%) TALD cases. Of these, 26 (4%) had died by the time of reporting. They were 
between 59 and 90 years old, and 21 were male. 

3.2.2 Clinical microbiology  

A total of 1 092 TALD cases (96%) were classified as confirmed; 49 (4%) were probable cases. Of 1 215 
laboratory tests used, 89% were UATs, 8% were PCRs and 4% were cultures (Table 16). 

Table 16. Reported diagnostic methods in travel-associated cases of Legionnaires’ disease, 2015  

Laboratory method 

n 

% 

Urinary antigen test (UAT) 

1 059 

87.2 

Nucleic acid amplification e.g. 
PCR 

Culture 

Single high titre 

Fourfold titre rise 

Total 

94 

48 

11 

3 

7.7 

4.0 

0.9 

0.2 

1 215  100 

Note: More than one method per case possible 

L. pneumophila serogroup 1 was reported as the causative microorganism in 770 (67%) TALD cases, whereas in 
362 (32%) cases the causative microorganism was unknown or not reported (Table 17). Monoclonal subtyping 
results were reported for cases with L. pneumophila serogroup 1 (14 cases, 1%): Benidorm (6 cases), Knoxville 
(4 cases), Allentown/France (2 cases), and Philadelphia (2 cases). The sequence type was reported for 17 cases 
(1%) from four countries: United Kingdom (6), Denmark (5), Sweden (4), and Germany (2). Three of the reported 
sequence types were ST 42, two were ST 23, and the others were a variety of single sequence types. 

21 

 
 
 
 
 
 
 
 
 
 
 
Legionnaires’ disease in Europe, 2015 

SURVEILLANCE REPORT 

Table 17. Reported species or L. pneumophila serogroup in travel-associated cases of Legionnaires’ 
disease, 2015 

L. pneumophila serogroup/L. species  Number/proportion of TALD cases  

1 

3 

6 

Mix of serogroups 

L. Longbeachae 

Pathogen unknown or not reported 

Total 

n 

770 

2 

2 

1 

4 

362 

1 141 

% 

67.5 

0.2 

0.2 

0.1 

0.4 

31.7 

100 

3.2.3 Travel: visits and sites 

The 1 141 TALD cases had made a total of 1 606 international journeys. Of these visits, 1 221 (76%) were within 
the EU/EEA, 353 (22%) were outside the EU/EEA ( 

Figure 11 and Figure 12), and 32 journeys were on ships. The three destination countries with most TALD-
associated travel visits were Italy (n=417, 26% of 1 606 visits), France (n=290, 18%), and Spain (n=130, 8%). 
For 17 visits, the accommodation type was not reported, which represents a 35% reduction in missing information 
compared with the previous year. Of the 1 589 visits for which the accommodation type was reported: 78% of the 
overnight stays were in hotels, 9% were on camping sites, 5% in apartments, 2% were on ships, and 2% were 
reported as other types of accommodation. 

Figure 11. Number of accommodation site visits and clusters of travel-associated cases of 
Legionnaires’ disease, by destination country, EU/EEA and neighbouring countries, 2015 

22 

 
 
 
 
 
 
 
 
 
 
 
 
SURVEILLANCE REPORT 

Legionnaires’ disease in Europe, 2015 

Figure 12. Number of accommodation site visits and clusters of travel-associated cases of 
Legionnaires’ disease, by destination country, worldwide, 2015 

3.2.4 Clusters 

In 2015, ELDSNet detected 167 new TALD clusters, 155 of which were standard clusters and 12 were complex 
clusters. The clusters were associated with accommodations in 32 countries (including ships) worldwide. There 
were four clusters on board ships, with a total of ten cases. 

Of the 167 clusters, 113 (68%) were comprised of two cases (Figure 13). The remaining clusters ranged between 
three and 12 cases. 

Figure 13. Number of cases of travel-associated Legionnaires’ disease per cluster, 2015 

23 

 
 
 
 
 
 
 
 
 
 
 
 
Legionnaires’ disease in Europe, 2015 

SURVEILLANCE REPORT 

In 60% of the clusters, the first two reported cases originated in different countries. Most of these clusters would 
probably not have been detected had it not been for the international surveillance of the ELDSNet network.  

The number of TALD clusters at subnational (NUTS2) level is shown in Figure 14. 

Based on the TALD surveillance scheme in 2015, 14 new and eight updates for rapidly evolving clusters were 
reported to tour operators.  

Figure 14. Number of standard clusters of travel-associated Legionnaires’ disease per destination 
area (NUTS2), EU/EEA, 2015 

3.2.5 Investigations and publication of accommodation sites 

For all 167 clusters, we received a preliminary (environmental) assessment report within two weeks of notification, 
followed by a final assessment report within six weeks of notification. Legionella was found in 60% (78/129) of all 
cluster sites where environmental water sampling results were reported. 

In 2015, the names of eight accommodation sites were published on the ECDC website, because assessment 
reports stated that satisfactory control measures were not implemented in a timely manner. 

3.3 Outbreaks (not travel-associated) 

In the new reporting scheme for community or healthcare-associated outbreaks, eleven countries reported 
between one and 20 outbreaks of two or more cases (54 in total). Of the 559 reported outbreak cases, 20 (3.6%) 
were reported to have died. Thirteen countries reported not having had any outbreak in 2015: Bulgaria, Cyprus, 
the Czech Republic, Greece, Malta, Latvia, Lithuania, Luxembourg, Norway, Slovakia, Ireland, Poland and Sweden. 
Six EU/EEA countries did not report.  

Nine countries reported 35 outbreaks of at least three cases: United Kingdom (10), Spain (9), France (4), 
Netherlands (3), Portugal (3), Hungary (2), Italy (2), Denmark (1), and Germany (1). One outbreak involved 304 
cases, six outbreaks with between 10 and 20 cases, and 28 with between three and nine cases.  

The three largest outbreaks occurred in Spain, Germany, and Portugal.  

Spain reported the largest outbreak with 304 cases, 278 of which were confirmed; 26 outbreaks were probable. 
Four cases died. Most cases occurred during two weeks in December in one town, Manzanares. The source could 
not be determined. Another outbreak in Spain involved 14 cases and was caused by a contaminated cooling tower.  

Germany experienced a large outbreak involving 19 cases, including one death (Bremen, November and 
December 2015). Legionella pneumophila serogroup 1 subtype Benidorm ST 2151 was detected in two patients. 

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Legionnaires’ disease in Europe, 2015 

This outbreak had a second wave at the beginning of 2016. Despite extensive epidemiological investigations, the 
source of infection was not found.  

Portugal reported an outbreak involving 17 cases, one of whom died, in an area close to a shopping centre in Porto 
with six cooling towers. No source could be identified.  

In fifteen of the outbreaks, the source was reported to have been found, and in another fourteen, a source was 
suspected. The suspected or confirmed source for seventeen outbreaks was reported to be the hot/cold water 
system, four outbreaks were connected to a cooling tower, and a further three could be linked to a spa pool. Ten 
different sequence types were reported. Sequence type 37 was found in two outbreaks, while all other sequence 
types were found only once. In eleven outbreaks, human and environmental isolates could be matched. 

25 

 
 
 
 
 
 
 
 
 
 
 
Legionnaires’ disease in Europe, 2015 

SURVEILLANCE REPORT 

4 Discussion 

With 7 034 cases reported, the notification rate of LD in the EU/EEA in 2015 was 1.37 cases per 100 000 
population, the highest ever observed. The overall notification rate increased over the 2011−2015 period. 

Four countries (France, Germany, Italy, and Spain) accounted for 69% of all notified cases although their 
combined populations only represent approximately 50% of the EU/EEA population. Many countries had a 
notification rate below 0.5 cases per 100 000 population, a situation unchanged over the past five years and 
unlikely to reflect the true incidence of LD in these countries. ECDC gives special attention to Bulgaria and Romania 
which only reported one and five cases in 2014 for populations of seven and 20 million, respectively. 

The main characteristics of the cases reported in 2015 were very similar to those reported in previous years: most 
cases were sporadic and community-acquired, and the disease affected mostly older males.  

Healthcare-associated cases were more likely to die most probably because they were more likely to have 
underlying conditions. Cases with a history of travel abroad had the lowest CFR. It is likely that people able to 
travel are overall in a better physical condition compared to those who cannot travel (‘healthy traveller effect’). 

Over the past five years, the proportion of cases reported to have been diagnosed by PCR has continuously 
increased from less than 2% in 2008 to 10% in 2015. PCR is increasingly recognised as an accurate and reliable 
diagnostic test for LD, possibility superior to UAT [17]. However, culture remains the gold standard, and the 
proportion of cases for which culture is performed remains low overall and varies substantially across countries.  

In 2015, 1 141 travel-associated cases of LD were reported, an increase of 20% for the second year in a row. This 
is in line with the increased overall Legionnaires’ disease notification rate. Further analyses may provide a better 
insight into the factors driving this year’s increase. 

A hundred fifty-five new standard travel-associated clusters were identified, over 50% more than only three years 
earlier. Sixty percent of the TALD clusters would most probably not have been detected without international 
collaboration, confirming the added value of ELDSNet’s daily TALD surveillance in protecting the health of travellers 
in the EU/EEA and other collaborating countries.  

26 

 
 
 
 
 
 
 
 
 
 
 
 
SURVEILLANCE REPORT 

Legionnaires’ disease in Europe, 2015 

5 Conclusion 

Legionnaires’ disease remains an important cause of preventable morbidity and mortality in Europe. Large 
outbreaks such as the one that occurred in Spain remind us of the challenges we face in preventing and controlling 
Legionnaires’ disease. 

ECDC gives priority assistance to countries with notification rates below one per million inhabitants in order to 
improve clinical awareness, laboratory diagnosis, and reporting of Legionnaires’ disease.  

In 2015, ELDSNET continued to demonstrate the effectiveness of daily TALD surveillance, the value of early 
detection, and the importance of following up on clusters. 

Regular checks for the presence of Legionella bacteria and appropriate control measures applied to man-made 
water systems may prevent cases of Legionnaires’ disease at tourist accommodation sites, in hospitals, in long-
term healthcare facilities or other settings where sizeable populations at higher risk may be exposed. 

27 

 
 
 
 
 
 
 
 
 
 
Legionnaires’ disease in Europe, 2015 

SURVEILLANCE REPORT 

References 

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Transmission of Legionnaires’ Disease. N Engl J Med. 2016 Feb 4;374(5):497–8.  

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of Legionnaires’ disease. Lancet Infect Dis. 2014 Jun;  

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Europe, 2009-2010. Eurosurveillance. 2013;18(10):20417.  

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8.   Van Hest NAH, Hoebe CJPA, Den Boer JW, Vermunt JK, Ijzerman EPF, Boersma WG, et al. Incidence and 

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[Internet]. Stockholm: ECDC; 2015. Available from: 
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