Legionellosis comprises clinical conditions triggered by Legionella species, primarily manifesting as Legionnaires' disease, a serious pneumonia, and Pontiac fever, a milder upper respiratory syndrome. These pathogens naturally inhabit freshwater environments, with Legionella pneumophila being the predominant agent responsible for sporadic cases and large outbreaks worldwide [1][2][5][4].
Disease overview
BacterialLegionellosis
军团菌病
Evidence-backed informationEN 5/7 applicable sections · ZH 5/7 applicable sectionsUpdated Sep 3, 2026
Legionellosis encompasses infections caused by Legionella bacteria, ranging from mild febrile illness to severe pneumonia known as Legionnaires' disease. It represents a substantial global health burden, frequently underreported but consistently documented with high incidence and significant healthcare costs. The condition remains a prominent cause of both community- and hospital-acquired pneumonia requiring intensive care [1][2][3][4].
Read the full clinical and epidemiological profile6
Symptom onset typically occurs two to ten days post-exposure, presenting with cough, dyspnea, high fever, myalgias, and headaches. Gastrointestinal disturbances like nausea, vomiting, and diarrhea frequently accompany the primary pulmonary symptoms. Severe progression often necessitates intensive care admission, characterized by profound lung injury requiring respiratory support, extrapulmonary manifestations, and non-specific laboratory abnormalities [1][2][3][4].
The pathogen exhibits a worldwide distribution, though reported incidence fluctuates significantly due to varying diagnostic capabilities and surveillance infrastructure. In regions with established monitoring, annual detection rates approximate 10 to 15 cases per million individuals, with overall numbers rising alongside improved molecular testing. Cases are classified by acquisition context, including community, travel, hospital, and increasingly recognized occupational settings. Population-level mortality estimates vary broadly from 4% to over 40%, heavily dependent on healthcare facility type, patient demographics, and intervention timeliness [2][5][3][4].
Infection occurs exclusively through inhalation of aerosolized water droplets or aspiration of contaminated liquids, with no evidence of direct human-to-human spread. Environmental reservoirs encompass natural freshwater bodies and engineered artificial systems such as cooling towers, hot water tanks, and potable water networks. Certain bacterial species also persist in horticultural substrates, establishing potting mixes as an alternative exposure route [1][2].
Mitigation relies primarily on rigorous engineering controls and systematic maintenance protocols for artificial water infrastructure to inhibit bacterial colonization and aerosol generation. Because prophylactic immunization is unavailable, public health strategies emphasize routine water quality monitoring, temperature regulation, and structural upkeep across residential, commercial, and institutional facilities [1].
- 1Wikipedia contributors. Legionnaires' disease - Wikipedia [Internet]. Wikipedia. cited 3 Sept 2026.Available from: https://en.wikipedia.org/wiki/Legionnaires'_disease
- 2World Health Organization. Legionellosis [Internet]. cited 3 Sept 2026.Available from: https://www.who.int/news-room/fact-sheets/detail/legionellosis
- 3Rello J et al. Severe Legionnaires' disease. Ann Intensive Care. 2024 Apr 2. PMID: 38565811. doi: 10.1186/s13613-024-01252-y.PubMed: https://pubmed.ncbi.nlm.nih.gov/38565811/
- 4Viasus D et al. Legionnaires' Disease: Update on Diagnosis and Treatment. Infect Dis Ther. 2022 Jun. PMID: 35505000. doi: 10.1007/s40121-022-00635-7.PubMed: https://pubmed.ncbi.nlm.nih.gov/35505000/
- 5Principe L et al. Legionellosis in the occupational setting. Environ Res. 2017 Jan. PMID: 27717486. doi: 10.1016/j.envres.2016.09.018.PubMed: https://pubmed.ncbi.nlm.nih.gov/27717486/
Coverage
Reporting countries and regions
AustraliaAU
AustriaAT
BelgiumBE
BulgariaBG
CanadaCA
CroatiaHR
CyprusCY
CzechiaCZ
DenmarkDK
EstoniaEE
FinlandFI
FranceFR
GermanyDE
GreeceGR
Hong Kong, ChinaHK
HungaryHU
IcelandIS
IrelandIE
ItalyIT
JapanJP
LatviaLV
LiechtensteinLI
LithuaniaLT
LuxembourgLU
MaltaMT
NetherlandsNL
New ZealandNZ
NorwayNO
PolandPL
PortugalPT
RomaniaRO
SingaporeSG
SlovakiaSK
SloveniaSI
South KoreaKR
SpainES
SwedenSE
SwitzerlandCH
Taiwan, ChinaTW
United KingdomGB
United StatesUS
Trends by reporting country
Monthly patterns over time
Research Radar
Recent related research
Legionella longbeachae and Legionellosis
Emerging Infectious Diseases
Literature links are provided for discovery and do not alter or validate the surveillance series above.
Data access
Page dataset index with source links and update metadata.
Official sourcesAuthority, cadence, notes55
Austria AGES Radar for Infectious Diseases
Austria
AGES Radar monthly national source. Internal ingestion retains native categories; public release is disabled pending licence review.
Australia NINDSS
Australia
Australian national notifiable diseases surveillance dashboard.
Australia NINDSS — Australian Capital Territory
Australian Capital Territory, Australia
Australian NINDSS monthly state/territory notifications for Australian Capital Territory, kept separate from the Australia national aggregate.
Australia NINDSS — New South Wales
New South Wales, Australia
Australian NINDSS monthly state/territory notifications for New South Wales, kept separate from the Australia national aggregate.
Australia NINDSS — Northern Territory
Northern Territory, Australia
Australian NINDSS monthly state/territory notifications for Northern Territory, kept separate from the Australia national aggregate.
Australia NINDSS — Queensland
Queensland, Australia
Australian NINDSS monthly state/territory notifications for Queensland, kept separate from the Australia national aggregate.
Australia NINDSS — South Australia
South Australia, Australia
Australian NINDSS monthly state/territory notifications for South Australia, kept separate from the Australia national aggregate.
Australia NINDSS — Tasmania
Tasmania, Australia
Australian NINDSS monthly state/territory notifications for Tasmania, kept separate from the Australia national aggregate.
Australia NINDSS — Victoria
Victoria, Australia
Australian NINDSS monthly state/territory notifications for Victoria, kept separate from the Australia national aggregate.
Australia NINDSS — Western Australia
Western Australia, Australia
Australian NINDSS monthly state/territory notifications for Western Australia, kept separate from the Australia national aggregate.
ECDC Surveillance Atlas — Belgium Annual Baseline
Belgium
Belgium annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
ECDC Surveillance Atlas — Bulgaria Annual Baseline
Bulgaria
Bulgaria annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
Canada PHAC CNDSS Annual
Canada
Canada is the national jurisdiction; subdivision feeds are registered separately.
Public Health Ontario IDTO Monthly
Ontario, Canada
Ontario-level current-year preliminary monthly case counts from Public Health Ontario's IDTO report.
Switzerland FOPH IDD
Switzerland
Switzerland FOPH/BAG IDD mandatory reporting API normalized to national case rows. Monthly series may use the dashboard CHFL aggregate where CH-only monthly series are not exposed.
ECDC Surveillance Atlas — Cyprus Annual Baseline
Cyprus
Cyprus annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
ECDC Surveillance Atlas — Czechia Annual Baseline
Czechia
Czechia annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
Germany RKI SurvStat 2.0
Germany
RKI SurvStat national weekly notification export; raw ZIP exports are retained and recent weeks are overwritten for revisions.
ECDC Surveillance Atlas — Denmark Annual Baseline
Denmark
Denmark annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
ECDC Surveillance Atlas — Estonia Annual Baseline
Estonia
Estonia annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
ECDC Surveillance Atlas — Spain Annual Baseline
Spain
Spain annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
Finland THL Infectious Diseases Register
Finland
Finland THL Infectious Diseases Register national monthly case counts. The current month is ingested as provisional and the latest three months are refreshed for source revisions.
ECDC Surveillance Atlas — France Annual Baseline
France
France annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
ECDC Surveillance Atlas — United Kingdom Annual Baseline
United Kingdom
United Kingdom annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
ECDC Surveillance Atlas — Greece Annual Baseline
Greece
Greece annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
Hong Kong, China CHP Notifiable Diseases
Hong Kong, China
Hong Kong, China CHP annual notifiable infectious disease CSVs normalized to national monthly totals
ECDC Surveillance Atlas — Croatia Annual Baseline
Croatia
Croatia annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
ECDC Surveillance Atlas — Hungary Annual Baseline
Hungary
Hungary annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
Ireland HPSC Notifiable Diseases Hub
Ireland
Ireland HPSC national weekly notifiable-disease totals from the official ArcGIS FeatureServer. Internal ingestion is enabled; public release remains disabled pending written redistribution permission.
Iceland Directorate of Health Annual Dashboard
Iceland
National annual case notifications by disease. Published values can be revised retrospectively and remain annual period totals.
Iceland Directorate of Health STI Dashboard
Iceland
Monthly STI diagnosis facts from laboratory and registry surveillance; the official dashboard is published on a quarterly schedule.
Iceland Directorate of Health Respiratory Dashboard
Iceland
ISO-week respiratory diagnosis counts. Hospitalizations, samples, and vaccination indicators are separate measures and are not counted as diagnoses.
Iceland Directorate of Health Historical Registry
Iceland
Historical official registry tables for 1997–2021, with annual totals and disease-specific monthly notification facts retained at source grain.
Iceland Directorate of Health Legacy ICD Monthly
Iceland
Historical Saga EHR ICD encounter counts for 1997–2020. This clinical measure is non-comparable with registry notifications and is kept separate.
ECDC Surveillance Atlas — Italy Annual Baseline
Italy
Italy annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
JP NIID Weekly
Japan
Japan weekly infectious disease surveillance via NIID/JIHS.
Korea KDCA EID
South Korea
Korea KDCA notifiable infectious disease OpenAPI or portal/KOSIS downloads aggregated to national monthly notification counts.
ECDC Surveillance Atlas — Liechtenstein Annual Baseline
Liechtenstein
Liechtenstein annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
ECDC Surveillance Atlas — Lithuania Annual Baseline
Lithuania
Lithuania annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
ECDC Surveillance Atlas — Luxembourg Annual Baseline
Luxembourg
Luxembourg annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
ECDC Surveillance Atlas — Latvia Annual Baseline
Latvia
Latvia annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
ECDC Surveillance Atlas — Malta Annual Baseline
Malta
Malta annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
ECDC Surveillance Atlas — Netherlands Annual Baseline
Netherlands
Netherlands annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
Norway FHI MSIS Statistics Bank
Norway
Norway FHI MSIS national monthly notifications from the official Allvis frontend API; adapter contract checks guard the unversioned endpoint.
New Zealand PHF Science Monthly Notifiable Diseases
New Zealand
PHF Science (formerly ESR) monthly notifiable disease surveillance data via internal globalID2 crawler
ECDC Surveillance Atlas — Poland Annual Baseline
Poland
Poland annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
ECDC Surveillance Atlas — Portugal Annual Baseline
Portugal
Portugal annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
ECDC Surveillance Atlas — Romania Annual Baseline
Romania
Romania annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
Sweden Public Health Agency SmiNet
Sweden
Sweden SmiNet national monthly reported cases from the official Public Health Agency statistics pages; public release is enabled with closed-month publication and revisable recent-month refreshes.
Singapore CDA Weekly Infectious Diseases Bulletin
Singapore
Singapore national weekly case notifications, combining the official data.gov.sg 2012–2022 CSV history with CDA annual workbooks from 2023 onward; 2023 weekly PDFs are retained as a source fallback.
ECDC Surveillance Atlas — Slovenia Annual Baseline
Slovenia
Slovenia annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
ECDC Surveillance Atlas — Slovakia Annual Baseline
Slovakia
Slovakia annual Member-State reported case counts from the ECDC Surveillance Atlas. Missing topic/year cells remain unknown and published zeroes are preserved. Data provided by ECDC based on data reported by EU/EEA Member States.
Taiwan, China CDC NIDSS
Taiwan, China
Taiwan, China monthly notifiable infectious disease open-data CSV feed.
US CDC NNDSS
United States
CDC National Notifiable Diseases Surveillance System provisional data.
US CDC NHSS HIV
United States
CDC NNDSS weekly data plus NHSS annual national HIV diagnoses