How to Test for Legionnaires’ Disease
Meta title: How to Test for Legionnaires’ Disease | Legionella Testing Guide
Meta description: Learn how Legionnaires’ disease is tested, when to seek medical help, and how Legionella water testing helps identify risk in buildings and water systems.
How Do You Test for Legionnaires’ Disease?
Legionnaires’ disease is a serious type of pneumonia caused by breathing in tiny water droplets contaminated with Legionella bacteria. It cannot usually be diagnosed by symptoms alone, because early signs can look similar to flu, chest infections, COVID-19, or other forms of pneumonia.
If Legionnaires’ disease is suspected, testing must be carried out by medical professionals. The most common clinical tests include a urine antigen test and a respiratory sample test, such as sputum culture or molecular testing. The CDC recommends using urine testing alongside lower respiratory testing where possible, because this gives a stronger basis for diagnosis.
When Should You Seek Medical Advice?
You should seek urgent medical advice if you have symptoms of pneumonia, especially after possible exposure to contaminated water sources such as showers, hot tubs, cooling towers, spa pools, or large building water systems.
Possible symptoms can include:
-
A persistent cough
-
Shortness of breath
-
Chest pain
-
High temperature or fever
-
Muscle aches
-
Headache
-
Confusion
-
Diarrhoea or sickness
The NHS advises people to get urgent medical help if they have symptoms that could suggest Legionnaires’ disease, particularly if they are at higher risk or have recently stayed in accommodation, used a hot tub, or been exposed to a building water system.
Medical Tests Used for Legionnaires’ Disease
1. Urine Antigen Test
A urine antigen test is one of the most commonly used tests for Legionnaires’ disease. It looks for signs of Legionella pneumophila serogroup 1, which is a common cause of Legionnaires’ disease.
This test is widely used because it can provide results relatively quickly. However, it does not detect every type of Legionella infection, which is why doctors may request further testing.
2. Sputum or Respiratory Sample Testing
A sputum sample is mucus coughed up from the lungs. This can be tested using culture or molecular methods to help detect Legionella bacteria.
Respiratory sample testing is important because it can help identify the exact strain involved. This can be especially useful during investigations into outbreaks, healthcare-associated cases, or suspected exposure from a particular building or water system.
3. Blood Tests and Chest Imaging
Doctors may also use blood tests, chest X-rays, or other investigations to assess pneumonia and the patient’s overall condition. These tests may support the diagnosis, but they are not usually the only method used to confirm Legionnaires’ disease.
Can You Test Yourself for Legionnaires’ Disease?
No. Legionnaires’ disease should be diagnosed by a qualified healthcare professional. If you feel unwell and think you may have been exposed to Legionella, you should contact your GP, NHS 111, or emergency services depending on the severity of your symptoms.
A home water test can detect the presence of Legionella bacteria in a water system, but it cannot diagnose Legionnaires’ disease in a person.
Testing Water for Legionella
While medical testing confirms whether a person has Legionnaires’ disease, Legionella water testing checks whether Legionella bacteria are present in a building’s water system.
Water testing may be recommended for:
-
Commercial properties
-
Landlord-managed buildings
-
Healthcare premises
-
Care homes
-
Hotels and guest accommodation
-
Gyms, spas, and leisure facilities
-
Buildings with showers, tanks, calorifiers, or complex pipework
-
Sites with cooling towers or evaporative condensers
Water samples are usually taken from outlets or areas of concern, such as showers, taps, tanks, calorifiers, or sentinel points. The samples are then sent to a laboratory for analysis.
Legionnaires’ Disease Testing vs Legionella Water Testing
It is important not to confuse the two.
Legionnaires’ disease testing is carried out on a person by medical professionals. This may involve urine, sputum, blood tests, and chest investigations.
Legionella water testing is carried out on water systems to identify whether Legionella bacteria are present and whether further control measures are needed. Both types of testing are important, but they serve different purposes.
Do All Buildings Need Legionella Testing?
Not every building needs routine water sampling, but all UK duty holders must assess and manage the risk from Legionella. The Health and Safety Executive explains that employers, landlords, and those in control of premises must identify and assess sources of risk, manage those risks, and keep appropriate records.
A Legionella risk assessment helps determine whether water testing is needed. Testing may be recommended if there are concerns about water temperature control, stagnation, poor system design, vulnerable occupants, previous positive samples, or suspected exposure.
What Happens If Legionella Is Found in Water?
If Legionella is detected, the next steps depend on the level of bacteria found, the type of building, who uses the premises, and the condition of the water system.
Action may include:
-
Reviewing the Legionella risk assessment
-
Checking hot and cold water temperatures
-
Flushing little-used outlets
-
Cleaning and disinfecting water systems
-
Removing dead legs or stagnant pipework
-
Descaling shower heads and outlets
-
Improving monitoring records
-
Retesting after remedial work
For higher-risk sites, professional advice should be taken quickly to reduce exposure and protect building users.
Book Legionella Testing or a Risk Assessment
If you are responsible for a workplace, rental property, healthcare setting, leisure facility, or commercial building, you have a duty to manage Legionella risk. A professional Legionella risk assessment can identify whether your water system presents a risk and whether laboratory water testing is required.
Need help with Legionella testing or risk assessment?
FAQs
How is Legionnaires’ disease diagnosed?
Legionnaires’ disease is usually diagnosed using laboratory tests requested by a healthcare professional. Common tests include a urine antigen test and testing of respiratory samples such as sputum.
Can a water test tell me if I have Legionnaires’ disease?
No. A water test can identify Legionella bacteria in a water system, but it cannot diagnose illness in a person. Medical testing is needed to diagnose Legionnaires’ disease.
How long does Legionella water testing take?
Laboratory times vary depending on the method used and the laboratory. Your water hygiene provider should confirm expected turnaround times before sampling.
Who is most at risk from Legionnaires’ disease?
People at higher risk include older adults, smokers, people with chronic lung disease, people with weakened immune systems, and those with certain underlying health conditions.
Is Legionnaires’ disease contagious?
Legionnaires’ disease is usually caught by breathing in contaminated water droplets. It is not usually spread from person to person.
Do landlords need a Legionella risk assessment?
Landlords and property managers have responsibilities to assess and control Legionella risk where they are in control of premises or water systems. The risk level will depend on the property and water system. HSE guidance sets out duties around identifying, assessing, and controlling risk.
The Dangers of Legionnaires’ Disease in the Community
Legionnaires’ disease is a serious type of pneumonia caused by breathing in tiny droplets of water containing Legionella bacteria. While it cannot be spread from person to person, it poses significant dangers within communities where water systems are not properly maintained.
Why It’s Dangerous
-
Severe illness – Legionnaires’ disease can cause high fever, cough, chest pain, and breathing difficulties. In some cases, it can be fatal.
-
Vulnerable groups at risk – Older adults, smokers, and people with weakened immune systems are especially vulnerable.
-
Hidden sources – The bacteria can grow in poorly maintained water systems such as cooling towers, showers, spa pools, fountains, and storage tanks.
-
Outbreak potential – If a contaminated system serves a community setting (e.g., hotels, hospitals, care homes, gyms, or public buildings), large numbers of people can be exposed.
Community Impact
-
Public health risk – outbreaks can affect multiple people at once.
-
Legal consequences – organisations may face enforcement action if found non-compliant.
-
Reputational damage – businesses, landlords, and facilities linked to outbreaks often suffer lasting trust issues.
Prevention is Key
The good news is that Legionnaires’ disease is largely preventable through proper water system management. This includes:
-
Regular Legionella risk assessments
-
Ongoing monitoring and water testing
-
Cleaning and disinfection of systems
-
Staff training and awareness
By taking proactive measures, communities can significantly reduce the risks and protect residents, tenants, and visitors.