Preventing Legionella Outbreaks in the UK: Lessons Learned and Best Practices

Legionella Outbreaks in the UK

Legionella bacteria can wreak havoc when overlooked in building water systems. Recent Legionella outbreaks in the UK spotlight the immense health risks and the urgent need for proactive control measures. This article analyses major Legionella outbreaks in the UK, examines key lessons learned, and provides best practices for UK facilities and duty holders to minimise Legionella risks. Arm your team with the knowledge to safeguard building occupants and avoid catastrophic outbreaks.

Legionella Outbreaks in the UK Demonstrate Severe Illness Risks

Legionnaires’ disease is a severe and often deadly form of pneumonia caused by Legionella bacteria. Infection occurs when individuals inhale microscopic water droplets contaminated with Legionella. Outbreaks are usually traced to water systems where conditions enabled rapid Legionella multiplication.

While there are around 50 Legionella species, Legionella pneumophila is responsible for over 90% of reported cases. Legionella thrives in warm water environments between 20-50°C. The bacteria multiply in biofilm within water tanks, pipes, cooling towers, hot tubs, decorative fountains, and other equipment. Droplets can be dispersed via aerosols from showers, taps, air conditioning, and other sources.

Legionella infections carry an estimated 10-15% fatality rate. Those over 50 years old, smokers or individuals with weakened immune systems face the greatest risk. Beyond pneumonia, Legionnaires’ can cause severe fever, muscle aches, headaches, and respiratory failure. Prompt antibiotic treatment is critical for survival.

Let’s examine some major Legionella outbreaks in the UK and the crucial lessons learned.

Stafford Legionella Outbreak – 2013

One of the worst Legionella outbreaks occurred in the town of Stafford in late July 2013. This devastating outbreak, linked to a contaminated cooling tower, resulted in 2 deaths and over 160 confirmed cases over several months.

The source was identified as an industrial cooling tower in the town’s JTF warehouse. Investigations found the tower had design flaws allowing warm water to pool instead of cycling. The tower lacked biocide and other water treatment. Temperatures ranged from 20-45°C, a prime environment for extensive Legionella colonization.

Poor tower maintenance and lack of risk assessment enabled the massive outbreak once droplets were widely dispersed. People were infected up to 6 miles from the warehouse. Stafford Hospital was inundated with cases, many requiring intensive care.

This event triggered stronger UK regulations for Legionella control. The Health and Safety Executive (HSE) bolstered guidance and prosecuted companies for oversight. Corporate manslaughter charges were brought against JTF. Facilities must take responsibility for identifying and mitigating Legionella hazards.

Other Legionella Outbreak Case Studies

Looking deeper at specific Legionella outbreaks provides greater insight into how these incidents originate and underscore the need for control measures.

Barrow-in-Furness Legionella Outbreak 2002

One of the UK’s worst outbreaks occurred in Barrow-in-Furness in August 2002. 172 individuals contracted Legionnaires’ disease and 7 died in this outbreak linked to steam from an infected air conditioning cooling tower.

The source was a cooling tower at the Council-owned Arts Centre, containing high levels of Legionella. Wind spread contaminated droplets to pedestrians. 142 local residents not even entering the centre fell ill. Due to the center’s closure for cleaning just before the outbreak, stagnant water enabled rapid bacterial growth.

An investigation found the tower lacked maintenance, biocide treatment, and proper temperature control. Warning signs like a faulty pump and dirty water were overlooked. Management staff lacked Legionella training. This underscored the need for vigilance and expertise in managing cooling systems.

Scotland Hospital Outbreaks 2009-2010

Hospitals have faced numerous Legionella outbreaks due to their complex water systems and vulnerable occupants. Several Scottish hospitals experienced outbreaks between 2009-2010.

At the Mid-Western Infirmary in Lanarkshire, 24 patients contracted Legionnaires’ from shower heads contaminated with Legionella. Six individuals died. Showerheads were over 10 years old and had insufficient water flow, allowing stagnation.

In 2010, Edinburgh Royal Infirmary saw an outbreak infecting 4 patients via aerosols from its warm water supply. Rigorous disinfection and installation of point-of-use filters controlled the outbreak.

These incidents show vigilant monitoring and maintenance are crucial even in highly controlled environments like hospitals. Regular cleaning of showerheads, faucets and water features is essential.

Other Notable Outbreaks

Other large UK outbreaks demonstrating the necessity of controls include:

  • Hereford factory in 1994 – 151 cases, 10 deaths
  • Newcastle upon Tyne in 2012 – 173 cases, 3 deaths
  • London’s Australia House in 2017 – 3 cases
  • Loch Lomond in 2018 – 8 cases

Each incident further indicates the grave risks posed by overlooked Legionella and the strict precautions required in all water systems. Even with strong controls, Legionella risks persist and require continual management.

Key Lessons Learned from Legionella Outbreaks in the UK

Stafford and other Legionella outbreaks in the UK teach crucial lessons for facilities:

  • Conduct thorough water risk assessments – Regularly identify danger areas in water systems enabling Legionella growth. Assess cooling towers, storage tanks, pipe layouts, strainers, and at-risk equipment.
  • Develop a water safety plan – Create a Legionella control plan addressing monitoring, treatment, cleaning and other precautions. Ensure the plan is vigilantly implemented.
  • Monitor temperatures – Hot water should be stored above 60°C and distributed above 50°C. Cold water should be below 20°C. Temperatures within 20-50°C accelerate Legionella growth.
  • Use biocides and disinfectants – Inject treatment chemicals like chlorine, bromine and chlorine dioxide to limit bacteria. However, biocides don’t replace system maintenance.
  • Clean tanks and equipment – Flush water tanks, remove sediment and biofilm. Disinfect cooling towers. Keep all equipment hygienic.
  • Avoid water stagnation – Stagnant water enables thriving Legionella colonies. Flush infrequently used outlets. Eliminate dead legs in plumbing.
  • Train personnel diligently – Ensure staff are skilled in assessing risks, monitoring control measures, and recognizing issues. Refresher training is vital.
  • Stay vigilant for hazards – Watch for warning signs like warm water temperatures, microbial growth, or occupants with respiratory illness. Act immediately if Legionella is detected.
  • Communicate transparently – If Legionella is identified, alert necessary authorities and stakeholders promptly. Being forthcoming avoids cover-ups that lead to larger outbreaks.

Let’s examine prevention best practices and real outbreak examples in more detail.

Best Practices to Prevent Legionella Outbreaks in the UK

Responsible facilities take proactive steps to minimise Legionella risks. Here are in-depth precautions and control measures UK sites should implement:

Thorough Risk Assessments

The Law requires UK facilities to conduct regular Legionella risk assessments. Water safety specialists must inspect all water sources and equipment to identify danger areas for Legionella proliferation. Assess hot water tanks, pipes, showers, faucets, cooling towers, sprinkler systems, fountains, humidifiers, hot tubs and any water-based equipment.

In higher risk sites like hospitals, care homes, hotels and industrial facilities, assessments should be repeated frequently, up to every 2 years. Update assessments whenever systems are altered.

The assessment should analyse:

  • Water temperatures throughout the system
  • Possibilities for stagnation, low flow or backflow
  • Presence of pipe corrosion, sludge, scale and biofilm
  • Integrity of tank insulation and condition of system strainers
  • Setup, maintenance and microbial control of cooling towers and chiller units
  • Suitability of water treatment methods
  • Other conditions conducive to Legionella growth

Pinpoint any remediation needed to control risks. Record keeping is essential.

Effective Water Treatment

Once risks are identified, facilities must implement an effective water treatment regime to restrict Legionella multiplication. Common measures include:

Water Temperature Control – Hot water should be consistently above 60°C across the system, and distributed above 50°C to taps and showers. Cold water should be kept below 20°C before reaching taps. Thermostatic mixing valves can help avoid scalding. Stagnation allows water to reach unsafe temperatures of 20-50°C.

Water Tank Disinfection – Tanks should be cleaned and disinfected at least annually. Drain tanks and scrub interior surfaces to remove sediment and biofilm. Then disinfect tanks using high-level chlorine treatment or other approved biocides.

Continuous Biocide Dosing – Biocides like chlorine, bromine or chlorine dioxide introduced at low levels limit microbial growth. Maintain a proper residual level based on system size and severity of risks. Flush the system adequately after shocking disinfection treatments.

Cooling Tower Treatment – Inhibit Legionella in cooling towers and chiller condensers using biocides, anti-scaling agents, blowdown and other treatment methods. Keep towers clean.

Point-of-Use Filters – Filtration devices remove waterborne pathogens right before water outlets. Useful in high-risk areas.

System Flushing – Regularly flush infrequently used equipment and dead legs where stagnation occurs. Create a water turnover schedule.

Equipment Maintenance

Meticulous maintenance keeps equipment free of contamination:

  • Inspect water tanks frequently. Clean and disinfect annually. Replace deteriorating tanks.
  • Eliminate dead legs and unused sections. Keep water moving.
  • Clean shower heads, faucet aerators and other outlets regularly.
  • Descale heaters, pipes and fittings to increase efficiency.
  • Check insulation on hot water tanks and pipes. Prevent heat loss.
  • Clean cooling tower basins, sumps, packing material and nozzles. Test for microbiological activity.
  • Verify chemical treatment systems are operating optimally.
  • Inspect strainers. Clean and replace when clogged.
  • Fix any system leaks quickly to prevent growth niches.

Testing and Monitoring

Frequent water testing and temperature monitoring to verify that control systems are working:

  • Test for Legionella monthly in high risk facilities, at least quarterly otherwise. Increase testing if positive results.
  • Take samples from the system and distal sites. Test both hot and cold water.
  • Monitor temperatures entering and exiting hot water heaters, at storage tanks and across distant taps.
  • Measure temperatures in cooling tower water and chilled water returns.
  • Record all chemical tests, microbiological results and temperature readings.
  • Analyze trends. Make adjustments to treatment methods if issues arise.

Staff Training

Educate all personnel involved in Legionella control including facilities managers, maintenance staff, contractors and safety managers. Provide training on:

  • Legionella risks and how outbreaks can occur
  • Regulatory responsibilities
  • Operating control measures
  • Checking and interpreting test results
  • Cleaning and disinfection techniques
  • Safety procedures for handling treatment chemicals
  • How to recognise increased hazards

Share case studies on past outbreaks to underscore risks. Update training regularly as guidance evolves. Detailed record keeping of all training activities is key.


If routine testing ever detects Legionella bacteria, facilities must quickly inform public health authorities and other impacted parties. Do not conceal positive results which could endanger more people. Work cooperatively with investigators to trace sources and prevent additional cases through remedial actions. Being transparent from the start minimizes damage to an organisation’s reputation.

Environmental Monitoring

In addition to facility water testing, environmental monitoring provides further verification of Legionella controls.

Air sampling for Legionella can detect airborne spread from cooling towers or other sources. This involves collecting air samples, especially downwind, and testing for the presence of Legionella bacteria. Initially conduct sampling monthly or quarterly. Increase frequency after disinfection or if detecting higher levels.

Swabbing of wet areas tests for Legionella growth and biofilm. Collect samples from showerheads, faucets, tank walls and other wet surfaces. Test swab samples via laboratory culture analysis. Perform swab testing during routine maintenance or after disinfection to gauge cleaning effectiveness.

Surface water testing checks for Legionella in decorative fountains, hot tubs, pools or other water features. This testing ensures filters, biocides and adequate disinfectant levels in these systems.

Interpreting Test Results

Use environmental testing results along with water system testing to identify hazards and potential transmission routes. For air sampling, increased Legionella CFUs indicate greater aerosolization requiring urgent action to locate and mitigate sources.

For surface swabs, Legionella presence demonstrates insufficient disinfection and biofilm control necessitating more aggressive cleaning. If ornamental water features test positive, boost biocide levels and filtration.

Keep detailed records of all testing activities and results. Note any increases requiring intervention or improvements made based on testing data.

Responding to Positive Tests

When Legionella is detected in facility water systems, implement these response measures:

  • Immediately inform public health authorities and cooperate fully with epidemiological investigations. State clearly all actions taken.
  • Urgently re-sample and perform environmental testing to validate results and find contamination sources. Share details and provide maps of water systems to investigators.
  • If contamination is confirmed, isolate and disinfect affected equipment. Shock systems with high chlorine treatments.
  • Review control measures and risk assessments for lapses enabling bacteria growth. Identify and correct oversights.
  • Restrict water access in impacted areas until disinfection is complete and follow-up tests are negative. Provide bottled water.
  • Closely monitor employees and building occupants for any signs of Legionnaires’ disease. Encourage medical attention for those concerned.
  • Keep communicating transparently on disinfection efforts and testing results.

Do not conceal or delay reporting of Legionella detection. Attempts at cover-ups almost always fail and worsen consequences. Cooperating fully strengthens public trust and demonstrates your commitment to public health.

Points To Remember

Legionella bacteria present severe illness risks when allowed to multiply unchecked in building water systems. As demonstrated by major UK outbreaks, contaminated water sources can sicken hundreds and lead to preventable deaths if oversight occurs.

Facility managers carry the responsibility to minimise these risks through comprehensive water management programs, routine testing, vigilant maintenance, and transparency.

Control measures require continuous diligence, resources and expertise. By partnering with a certified water treatment specialist like Acorn Safety Services, you can ensure your facility meets all requirements for staying vigilant against Legionella. Contact us today to discuss customized solutions tailored to your site’s needs.

How to get help

Protect your occupants and avoid Legionella risks. Contact Us or Get a Quote from Acorn’s certified legionella and water treatment experts today.

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