England and Wales recorded 346 legionellosis cases in 2025, UK health surveillance data shows

4 min read|824 words

✓ Editorially Reviewed by Prof. Giorgi Pkhakadze, MD, MPH, PhD — GMJ News Desk

The National Enhanced Legionnaires’ Disease Surveillance Scheme (NELSS) has published comprehensive epidemiological data on confirmed legionellosis cases across England and Wales for 2025. The annual report, compiled from national surveillance scheme reporting forms and validated against Office for National Statistics (ONS) census population estimates, documents all cases with symptom onset between 1 January and 31 December 2025 that met defined clinical and laboratory diagnostic criteria.

Key takeaways

346 confirmed legionellosis cases were reported in England and Wales during 2025, representing the most complete dataset from NELSS since the scheme’s inception
Cases are stratified by exposure category—community-acquired, healthcare-associated, and travel-related—revealing distinct epidemiological patterns
The report examines how the COVID-19 pandemic altered Legionella transmission patterns, case demographics, and seasonal distribution
Regional variation in case incidence is documented alongside age-sex demographic breakdowns to guide targeted public health interventions

346

confirmed legionellosis cases in England and Wales with symptom onset in 2025, according to NELSS surveillance data

Legionellosis case distribution by exposure category, England and Wales, 2025

Confirmed cases (N=346) stratified by source of exposure

Community-acquired

215

Travel-associated

Healthcare-associated

Source: NELSS (National Enhanced Legionnaires’ Disease Surveillance Scheme), 2025 | GMJ News

Surveillance scope and methodology

The NELSS dataset covers all confirmed cases of Legionella infection among England and Wales residents with verified clinical and laboratory diagnoses. Cases meeting the surveillance scheme’s criteria—which include positive culture, serology, or nucleic acid detection—are enrolled in the national tracking system operated by the UK Health Security Agency (UKHSA).

Submit Your Paper

The report integrates surveillance data with ONS population census figures to calculate age-stratified and region-specific incidence estimates. This allows epidemiologists to identify high-risk populations and geographical clusters where targeted water safety and infection prevention measures may be warranted.

Pandemic-related epidemiological shifts

A key focus of the 2025 analysis examines how COVID-19 altered Legionella transmission patterns. The surveillance report documents shifts in case demographics, seasonal distribution, and exposure category proportions comparing pre-pandemic (2019), acute pandemic (2020–2021), and recovery periods (2022–2025). Travel-associated cases, historically a substantial proportion of legionellosis incidence, showed marked fluctuation during international travel restrictions and have since recovered as mobility normalised.

Healthcare-associated legionellosis cases—acquisitions within hospitals or long-term care facilities—required particular scrutiny during the pandemic when water system maintenance and infection control practices were disrupted. The 2025 data allows infection prevention teams to assess whether nosocomial transmission has returned to pre-pandemic baseline rates.

Regional variation and targeted prevention

The report presents confirmed case numbers disaggregated by region, age category, and sex. This granularity enables UKHSA and local health protection teams to identify clusters requiring urgent investigation. When multiple cases share exposure sites—such as cooling towers, fountains, or hot water systems—cluster investigation protocols activate, including environmental sampling, source identification, and remediation guidance to building owners.

Regional variation in legionellosis incidence may reflect differences in water infrastructure age, population density, and healthcare facility density. Areas with ageing water systems or large numbers of immunocompromised residents (e.g., near transplant centres) warrant enhanced surveillance and water safety management.

The National Enhanced Legionnaires’ Disease Surveillance Scheme documented 346 confirmed legionellosis cases across England and Wales in 2025, with 62% (215 cases) classified as community-acquired, 28% (97 cases) as travel-associated, and 10% (34 cases) as healthcare-associated, demonstrating recovery toward pre-pandemic epidemiological patterns.

— UK Health Security Agency, National Enhanced Legionnaires’ Disease Surveillance Scheme Annual Report, 2025

What this means

For patients: Anyone experiencing fever, cough, and respiratory symptoms weeks after visiting hotels, cruise ships, or large public buildings with water systems should notify their clinician of travel history, as travel-associated legionellosis requires specific antibiotic therapy (fluoroquinolones or macrolides) and may present atypically in older or immunocompromised individuals.

For clinicians: The 2025 surveillance data reinforce that Legionella pneumophila remains a significant cause of community-acquired and nosocomial pneumonia. Diagnostic suspicion should remain high in patients with severe pneumonia and travel history, failure to respond to standard beta-lactam therapy, or hyponatraemia—unusual in typical bacterial pneumonia. Urine antigen testing is rapid and sensitive; sputum or bronchoalveolar lavage culture and PCR are gold standards.

For policymakers: Regional surveillance stratification allows targeted water safety inspections and cooling tower regulations in high-incidence areas. The pandemic’s impact on healthcare-associated cases highlights the need for robust water system maintenance protocols in hospitals and long-term care facilities, including routine legionella testing, temperature monitoring of hot water systems, and staff training in infection prevention.

Next steps for public health action

The UKHSA uses annual surveillance data to refine risk assessment tools and prioritise building inspections. Water companies and facility managers receive guidance on engineering controls (maintaining water temperatures above 50°C, biocide treatment, and regular flushing of unused pipes). For more information on legionellosis prevention in healthcare settings, clinicians may consult official UKHSA legionnaires’ disease guidance.

The publication of 2025 surveillance data also supports European epidemiological comparisons through the European Centre for Disease Prevention and Control (ECDC), which coordinates legionellosis surveillance across EU and EEA countries. UK data feed into the annual ECDC legionellosis surveillance report, enabling identification of international clusters—particularly among travellers—and harmonised prevention strategies.

Source: Official Statistics: Legionellosis in residents of England and Wales: 2025

Was this article helpful?