Legionella exposure occurs through tiny water droplets, known as aerosols, released from sources such as showers, hot tubs, cooling towers and other water systems. This means the risk is not confined to public or commercial spaces. It can also exist within private properties, including the home.
Research suggests that up to 1.5 million households in the UK could be harbouring Legionella bacteria. When inhaled, these bacteria can cause Legionnaires’ disease, a serious infection that may lead to life-threatening pneumonia and, in severe cases, organ failure.
Infection occurs when contaminated aerosols are inhaled, allowing the bacteria to enter the lungs. Historically, Legionnaires’ disease has most commonly been associated with large buildings such as hotels, hospitals and office blocks, where complex water systems can allow bacteria to proliferate if controls fail.
However, evidence shows that Legionella is not limited to large premises. Public health researchers have identified a growing presence of Legionella in domestic environments, with household showers now recognised as a potential source of exposure.
Legionella bacteria thrive in stagnant water, particularly at temperatures above 20°C. Showers, taps and wash basins can become contaminated if they are left unused for extended periods. Even garden hosepipes may present a risk if water is allowed to stagnate and warm in sunlight.
LEGIONNAIRES’ DISEASE AND OUTBREAKS
In 2024, 472 Legionnaires’ disease cases were reported in the UK, while across Europe, infection rates are higher. The European Centre for Disease Prevention and Control has reported record case numbers in recent years, with the fatality rate also rising to 10%.
Early symptoms often include fever, loss of appetite and headaches. Within days, the infection can progress to severe pneumonia and heart failure. Recovery can be prolonged, with some patients enduring long-term symptoms with large impacts to health-related quality of life.
LEGIONELLA IN DOMESTIC SHOWERS ACROSS THE UK
Public Health England scientists investigated how common Legionella is in ordinary home showers by testing 99 showers in 82 properties across southern England. Using both water samples and swabs, they found clinically relevant Legionella species growing in roughly 1 in 12 showers, affecting 6% of households they visited. When they looked with more sensitive molecular tests (qPCR), almost a third of showers showed evidence of Legionella DNA, confirming that many domestic systems can harbour the bacteria even when people feel well.​
The researchers concluded that household showers can act as significant reservoirs of Legionella and should be taken seriously when investigating sporadic community cases of Legionnaires’ disease. They also showed that simple habits—such as using showers more frequently and cleaning showerheads more often—were linked to lower levels of Legionella, underlining the value of straightforward hygiene advice in cutting everyday risk.​
WHAT SHOULD ORGANISATIONS DO TO REDUCE LEGIONELLA RISK?
For organisations responsible for buildings, estates or shared facilities, controlling Legionella risk requires a structured and proactive approach. Showers and other high-risk outlets should be included within a documented water management plan, with clear responsibilities for flushing, inspection and maintenance, particularly following periods of low occupancy.
Routine cleaning and descaling of shower heads and hoses is essential, as biofilms and scale provide protective environments for bacteria to persist. Temperature control, flow management and disinfectant residuals should be regularly reviewed to ensure systems are operating within safe parameters.
Targeted testing plays a critical role in verifying that control measures are effective. Routine monitoring helps identify changes in system behaviour early, allowing corrective action to be taken before risk escalates or disruption occurs. Where buildings serve vulnerable populations or experience variable use, more frequent checks may be justified.
By combining good system design, consistent maintenance and reliable testing, organisations can demonstrate control, support compliance and protect the health of occupants, staff and visitors.
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