Legionnaires’ disease is a serious and potentially fatal illness. This post covers what it is, its causes, symptoms, treatment, and recovery process. We also discuss how to prevent Legionella and the legal requirements for employers and building owners/operators to protect staff and visitors from Legionnaires’ disease.
What is Legionella?
Legionella is a bacterium that causes Legionnaires’ disease. It thrives in stagnant water at temperatures between 20–40 degrees Celsius. You might find it in mouldy, rusty, or dirty areas. Although it occurs naturally, it can enter water systems in urban and suburban areas where conditions are favourable for growth.
Types of Diseases caused by Legionella
Legionellosis includes two diseases – Legionnaires’ disease and Pontiac fever – caused by exposure to Legionella bacteria.
Legionnaires’ Disease / Legionella Pneumophila
Legionnaire ‘s disease primarily affects the lungs. Symptoms include cough, shortness of breath, fever, and muscle aches. Early detection and treatment are critical for recovery. Testing water systems is essential to prevent outbreaks and protect public health.
Pontiac Fever
Pontiac fever is a milder illness caused by Legionella. Symptoms include flu-like signs such as chills, headache, and muscle pain. It is not as severe as Legionnaires’ disease and usually resolves without treatment. Always consult a healthcare provider for concerns.
Causes
People can get Legionnaires’ disease by breathing in water droplets with Legionella bacteria. This bacteria can grow in hot and cold water systems, air conditioning systems, humidifiers, cooling towers, and spa pools. It thrives when water temperatures are between 20-45°C, where nutrients like rust, sludge, scale, sediment, and algae are present, and where water stagnates (e.g. when a shower head and hose, or taps are not used regularly).
Legionella is rarely found in homes due to good water turnover. It’s more common in hotels, hospitals, and offices where the bacteria can enter the water supply and grow. People might get infected from water spray, such as from a shower or spray tap. Although Legionella can be found in ponds, lakes, and rivers, these are unlikely sources of infection.
Sources of Infection
Common sources of infection include:
- Showerheads, hoses along with sink and basin outlets
- Hot tubs
- Decorative fountains and water features
- Hot water calorifiers, cylinders and storage heaters
- Large, complex plumbing systems
- Cooling towers
Legionella Symptoms
Symptoms of the disease generally appear 2 to 10 days after infection. Unfortunately, there are no specific symptoms, and not everyone exposed to the bacteria develops them. Early signs resemble the flu and may include:
- high temperature, fever, and chills;
- cough;
- muscle pain;
- headache;
- Legionella pneumonia;
- rarely, diarrhoea and mental confusion.
Risk factors
Certain risk factors increase susceptibility to the disease, with smoking and chronic lung disease being the most common. Organ transplant recipients and those taking corticosteroid medications are at higher risk. Men are about three times more likely to contract the disease than women. Vulnerable groups include:
- Smokers, as smoking harms the lungs and increases the risk of lung infections.
- Individuals with weakened immune systems, often due to HIV/AIDS or specific medications, especially corticosteroids and drugs for organ transplant rejection prevention.
- People with chronic lung diseases or serious conditions like emphysema, diabetes, kidney disease, or cancer.
- Individuals aged 50 or older.
Complications
Legionnaires’ disease can lead to serious complications. Respiratory failure happens when lungs can’t supply enough oxygen or remove enough carbon dioxide. Septic shock occurs when a severe drop in blood pressure reduces blood flow to vital organs like the kidneys and brain. The heart tries to compensate but eventually weakens. Acute kidney failure is when kidneys suddenly lose the ability to filter waste from the blood, causing fluid and waste to build up in the body.
Treatment and Recovery from Legionella
Legionnaires’ disease needs antibiotic treatment. Most cases can be treated successfully. Early detection and treatment improve recovery chances. Healthy individuals usually recover but often need hospital care.
Required Conditions for Legionella Growth
To prevent Legionella growth, specific conditions must be met. Regular maintenance of water systems is essential to minimise the risks associated with Legionnaires’ disease.
- When the water is maintained between 20–45°C
- When the water contains nutrients
- When the water is stagnant.
Legionella Control
Stopping Legionella isn’t just luck. It takes real planning. Every building – especially big ones – needs a detailed risk assessment. The law often says you must do this. Look at possible risk, record what you find, and make a plan. The safety executive or site manager will make sure rules are followed and the approved code is used.
How to Test for Legionella Bacteria?
When inspecting water systems, look for visual warning signs that suggest a higher risk of Legionella bacteria, sample the system water via an independent UKAS Laboratory.
Legionella Sampling
Taking water samples isn’t tough if you follow the rules. Get samples from taps, cooling towers, shower heads, or hot tubs. The sampling method must keep things clean and clear of any other germs. Send samples to a UKAS accredited laboratory for the proper tests. By checking these, you’ll see if there’s a risk.
Corrosion
Corroded pipes, fittings, or valves can promote biofilm growth. This biofilm can shield Legionella bacteria from disinfection. Rust-coloured water or flakes and rust particles signal corrosion.
Scale
Scale buildup creates an ideal environment for bacteria like Legionella to grow. You can spot scale by looking for white or off-white deposits on faucets, showerheads, or inside plumbing.
Sediment
Sediment like dirt, debris, scale or particles can provide nutrients that help Legionella bacteria grow. Brown or cloudy water, or visible particles, may indicate sediment presence.
Legionella Test Results
After your lab checks the water samples, you’ll get test results. Sometimes they’ll show no bacteria, and sometimes they’ll show dangerous levels. How much legionella there is tells you what to do next. Clean, repeat testing, or maybe flush or close off parts of the water supply. Always follow up after testing.
Detection of Legionella Techniques
Legionella is isolated from water through filtration, heat or acid treatment, and plating on BCYE agar. GVPN media uses natamycin instead of cycloheximide. MWY agar contains dyes for colony identification. Incubate up to 10 days at 36°C. Rapid methods like PCR and immunoassays provide quick results. The ISO/TS 12869 standardises Legionella detection using qPCR.
IDEXX’s Legiolert detects L. pneumophila at a one-cell level in 100ml samples, using a substrate for a colour change within 7 days. Lateral flow assays identify Legionella within 25 minutes by running collected water through a filter and then applying it to a test stick.
Legionella in Hot and Cold Water Systems
Hot and cold water systems both need work to stay safe. Cold water systems can get warm in summer. Hot water should never drop below 60°C. Make sure water moves well and check temperatures often. When you do these things, Legionella has less chance.
Cooling Systems
Cooling systems, such as cooling towers and evaporative condensers, are high-risk areas for Legionella growth. These systems often involve water recirculation, which can create ideal conditions for bacteria. Regular cleaning, disinfection, and water treatment are essential to control Legionella. Monitoring water quality and maintaining proper temperatures are also critical. A well-maintained cooling system reduces the risk of Legionella outbreaks and ensures compliance with health and safety standards.
4 Ways to Prevent Legionella Bacteria in Commercial Water Systems
After conducting a Legionella Risk Assessment, establish a system to manage identified risks. This may involve:
1. Temperature monitoring
Keep hot water above 50°C and cold water below 20°C. This prevents Legionella bacteria from growing and kills them in hot water over time.
2. Cleaning routines
Regular cleaning stops Legionella bacteria from growing and multiplying.
3. Water Management
Regularly test water samples for Legionella bacteria. The risk assessment will determine the level of risk and how often these tests should be performed to ensure that bacteria levels are safe.
4. Chemical dosing using biocides
This method effectively controls Legionella, microorganisms, biofilm, and other harmful pathogens in water systems. Chlorine dioxide or stabilised hydrogen peroxide are most commonly used but note these should be considered as a last resort.
First Steps in Preventing Legionella Bacteria
The first step is to appoint someone competent to assess the risk of Legionella bacteria in the building’s water systems. Every business and building is different, so the responsible person must understand how their specific systems operate. They must complete Legionella training to manage the system properly.
Who can Carry Out a Legionella Risk Assessment?
A Legionella risk assessment must be thorough and specific to the building. Comfort Services Group can help assess and manage risks effectively. Trained personnel should regularly evaluate the water systems to identify potential hazards. This ensures compliance with health guidelines and protects occupants from Legionnaires’ disease. Regular maintenance and testing keep the water systems safe. Implementing these measures will reduce the chance of Legionella growth.
FAQs
Can you get Legionella from droplets of water?
Yes, Legionella bacteria spread through tiny water droplets in the air. These droplets can come from sources like showers, cooling towers, or fountains. Breathing them in can lead to infection, especially in vulnerable individuals. However, it cannot spread from person to person.
What is an acceptable level of Legionella in water?
For all water systems except cooling towers, a concentration below 1 CFU/mL (1,000 CFU/L) is at the detection limit. Legionella growth might occur between 1 and 10 CFU/mL (1,000 to 10,000 CFU/L).
What is the ISO test for Legionella?
ISO 11731:2017 outlines methods for isolating Legionella and estimating their numbers in water samples. These methods apply to all types of water, including drinking, industrial, waste, and natural sources.
How often should Legionella testing be carried out?
For simple buildings with low risks, review your risk assessment every two years. Update it sooner if there are significant changes.
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