Ferries And Cruise Ships Legionella Testing

Are you looking for ferries and cruise ships legionella testing in the UK? Find out why testing matters for cruise ships and how to deal with an outbreak of legionnaires’ disease.

Legionella risk in cruise ships and ferries

Keeping ferries and cruise ships safe isn’t negotiable. On maritime vessels of all sizes—from local ferries to the grandest cruise liners—robust water safety and targeted control are vital to protect passengers and crew from legionnaires disease, a serious lung infection caused by legionella bacteria (not spread by person to person contact). 

This guide explains why diligent water testing, smart design, and disciplined maintenance are essential, and how water safety specialists can help you meet your health and safety obligations.

Why ships face higher water safety risks

Closed spaces, complex water systems, and varied operating profiles mean ships have many critical points where waterborne pathogens can thrive. 

Warm recirculating loops, showers, spa pools, hot tubs, swimming pools, and decorative fountains can generate water droplets and water vapour or legionella carrying mist. 

When contaminated water droplets (or legionella contaminated water droplets) are inhaled—even after brief exposure—people may contract legionnaires disease, a lung infection caused by legionella pneumophila (including legionella pneumophila serogroup 1 and legionella spp 2-14).

Factors that raise risk aboard maritime vessels include:

• Variable temperatures and stagnation in water distribution systems, long water pipes, blind ends, and dead legs.
• Intermittent demand on water services during regular journeys that last only a few hours or long periods at sea.
• Humid plant spaces and air conditioning systems, occasional cooling towers, and aerosol generation near water distribution points.
• Smaller vessels, smaller ships, and smaller pleasure vessels or a small pleasure boat often receive little or no attention compared with larger ships and passenger ships, yet the bigger risks sometimes sit where the bigger risks lie—in older, poorly maintained infrastructure.

Controlling Legionella on ferries

Ferries have been utilised for all kinds of reasons, such as regular journeys completed within a few hours, or perhaps those customers and passengers spending longer durations on board.

One Example Is When Out Of An Approximate Ten Tested Ferries, 70% received positive tests for serogroup one strains of Legionella Pneumophila, 80% were positive for the serogroup 2-14 strain, which is not as severe but still poses a threat to the health of your guests, whether in the long-term or short-term.

Cruise ships testing positive for Legionella

We Have Previously Mentioned That Legionella Proliferation Research Tells How Competent Persons Rigorously Tested Six Cruise Ships Examined For The Same Strain Of Legionella Bacteria.

They tested them in Legionella serogroups of 1 and 2-14, all as common antigens, sometimes called serocomplex. The positive samples collected used from sampling points were tiny. The ships they tested that came out positive for Legionella were much smaller; they recorded that in one-third of the tested cruise ships, Legionella contamination was found positive for the dangerous sg 1, and at least 16% were found positive for the sg 2-14 variant.

Several companies and people spend time investing in the grandest, newest and most extensive ships; therefore, it makes more sense for them to be far safer than aged ships that rely on older systems for plumbing and water services.

Especially newer cruise ships that let hundreds of guests and passengers travel across many seas. While this is the case, it also is a massive indicator that there is an immense need for cruise liners to be more attentive toward your cold and hot water systems' overall treatment and condition.

That way, you can ensure all Legionella associated risks are efficiently and properly managed.

Thousands of guests and cruise ship passengers are exposed to the disease whilst you are on board in various ways, including the numerous other potable water systems, such as:

Rid all moist chambers, wall slime, limescale and all forms of dirt and grime from your systems, as this will allow you to ensure no legionella bacteria are growing in these areas. 

What the evidence says

Multiple prevalence reports and audits in Europe (including Italy, Sicily, and Mar) and the UK note tested ships returning positive results for legionella. In one prevalence study, cruise ships tested across serogroups found tested positive rates for sg 1 and sg 2-14 (2-14). 

In another dataset, six cruise ships were examined, and cruise ships tested positive for legionella spp, underlining public health implications. 

Names often appearing in academic summaries—such as mouchtouri va, goutziana g, laganà p, stathakis ne, masia md, deriu mg, piana a, sotgiu g, dettori m, karanika m, de giglio o—reflect the breadth of biomedical and dental sciences and dental sciences research on shipboard water. 

You’ll also see journals like BMC Public Health, Commun Dis Public Health, Ann Agric Environ Med, Environ Res, Int J reports, and USM/SG notes (sg 1, sg 2 14) cited in technical literature.

Takeaway: audits repeatedly find contamination hot-spots; risk assessments and effective management lower incidence; and safety lapses can lead to outbreaks with real potential fallout for business and public health.

Legal duty and practical responsibility

In the UK, health and safety law sets a legal requirement for duty holders to manage legionella risks. Operators, managers, and commercial boat owners must:

• Conduct a legionella risk assessment and keep it properly managed and completed.
• Put a documented water safety plan in place with specific control measures (and more specific control measures where indicated).
• Use water safety specialists and marine specialists for independent compliance auditing and qualitative and quantitative identification of legionella spp at critical points.
• Adopt corrective actions promptly and record corrective actions taken.

Why it matters: Prosecuting authorities can act where safety obligations and health and safety obligations are ignored. Reputational dangers are real; people spend holidays and work assignments on ships and expect them to be safe.

Typical testing scope on ferries and cruise ships

A modern programme covers water and air samples from multiple lines of defence:

Potable water systems / potable water:

• Temperature profiling across the entire water supply system.
• Flushing effectiveness checks at outlets with low use on board.
• Culture or rapid methods targeting legionella pneumophila and broader legionella spp.

Water systems that aerosolise:

• Showers, spray taps, spa pools, hot tubs, swimming pools, and decorative features.
• Cleaning and disinfection verification, biofilm control, and filter integrity.

HVAC and adjacent plant:

• Air conditioning systems checks; occasional air samples and air and ice samples where appropriate, plus ice samples from service stations.
• Where present, cooling towers (or process towers) associated with chillers.

Supporting sampling:

• Sentinel outlets at water distribution points; samples collected during high-risk scenarios (post-refit, after lay-up, or docked periods).
• On some audits, air samples collected near aerosol sources to capture mist behaviour.

Turnaround: Modern, validated rapid tests can give actionable screening results in only a few hours; culture confirms identity/viability on a longer time frame. For remote routes off shore, fast triage helps teams adopt interim control practices while culture is pending.

Designing an effective Water Safety Plan

A good shipboard water safety plan is a living document built around risk assessments and control:

• Identify many critical points (by deck, zone, and loop) and assign action limits.
• Keep temperatures out of the 20–45 °C range where legionella multiplies easily.
• Engineer out dead legs; review construction drawings before refits; replace non-compliant materials.
• Schedule flushing for cabins with low occupancy; control disinfectant residuals at distal points; validate treatment.
• Train teams so owners, operators, and ship managers know what steps to take when limits are exceeded.
• Include a clear outbreak plan with disease control escalation (shipboard and port coordination).

This structured approach helps ensure effective control practices are maintained and managed, even as operation profiles change.

Common scenarios and what to do

Post-refit surprises:

New pipe runs create stagnation pockets. Response: verify flushing, temperatures, and residuals; sample; adopt corrective actions.

Change in voyage pattern:

From day trips (only a few hours) to multi-day cruises: stagnation patterns shift. Response: adjust flushing and sampling windows accordingly.

Outbreak indicators:

Clusters of pneumonia-like illness on board. Response: activate outbreak plan, increase sampling, communicate with authorities, and implement prevention protocols.

Special considerations by vessel type

Cruise ships / cruise liners / many cruise ships

High passenger turnover and numerous amenities increase exposure points. Keep close watch on distal outlets and leisure features; ensure cruise ships preventive measures remain in place and up to date.

Ferries

High frequency regular journeys can lower stagnation, but overnight routes and seasonal lay-ups raise legionella risks; target tanks and loops used less often during the week.

Cargo ship and other maritime vessels (including yachts, motorboats, and smaller pleasure vessels)

Fewer passengers but similar opportunities for biofilms in under-used lines. Duty holders still must meet the same safety standards as other maritime vessels and ships and vessels used by the public.

Outbreak response: from detection to recovery

When legionella contamination is suspected or confirmed (tested positive), move fast:

• Isolate affected lines/areas; provide alternative drinking water.
• Evaluate water quality data; map sources; escalate action in your plan.
• Apply thermal or chemical control; retest to confirm reductions in legionella pneumophila and legionella spp.
• Keep transparent logs—these resources support independent compliance auditing and show the plan was designed and executed with effective management.

How water safety specialists support you

Water safety specialists bring a specialist area skillset to controlling legionella on ships:

• They conduct formal risk assessments and targeted sampling, including air samples or ice samples where relevant.
• They guide suitable precautions and preventive measures, validate control practices, and provide water safety specialists support during incident response.
• They help businesses involved to balance practicality and protection with an objective eye, so owners and operators can protect people and keep operations safe.

Key terms you’ll encounter on reports (demystified)

• Legionella / legionella bacteria / legionella pneumophila / legionella spp: the pathogens behind legionnaires disease.
• Tested positive / positive: detection above reportable limits.
• Risk assessments: formal reviews of water systems and aerosol sources; the bedrock of control.
• Qualitative and quantitative identification: confirms presence and estimates concentration.
• Aboard ships legionella survives: shorthand in some reports for resilience in complex loops if not controlled.

Practical checklist (keep it simple on board)

• Keep hot water ≥ 60 °C at calorifiers; ≥ 50 °C at outlets (or agreed equivalent control using biocide).
• Cold water ≤ 20 °C at outlets.
• Flush low-use outlets.
• Service TMVs, strainers, and filters.
• Clean and descale outlets, remove visible biofilm.
• Log every check; investigate any positive or higher levels found.
• Review sampling scope annually or after significant changes.

Ferries And Cruise Ships Legionella Testing: Final word

Whether you run ferries and cruise ships or other maritime vessels, your best defence is a living water safety plan, frequent water testing, and timely action. With the right water safety specialists, you’ll mitigate legionella risks, keep passengers and crew safe, and stay responsible to both public health expectations and your health and safety obligations/safety obligations.