Experts are warning of a surge in Legionnaires' disease cases as the UK experiences a heatwave with temperatures reaching 38°C. The potentially fatal lung infection, caused by inhaling water droplets containing Legionella bacteria, thrives in warm, stagnant water systems like hot tubs. According to new research, one in ten Brits now owns a hot tub or jacuzzi, equating to nearly 3 million units nationwide, while another one in ten has a swimming pool or cold plunge bath.
Lack of Maintenance and Testing
More than half of hot tub owners admit they are not fully confident in their cleaning routines. Among them, 28% have not considered or prefer to ignore hygiene risks. A staggering 92% do not regularly test for Legionella despite the serious health consequences. Hydrohawk, the UK's leading Legionella authority, warns that intermittent use during fluctuating hot and wet spells creates ideal conditions for bacteria growth, as water stagnates in plumbing, disinfectant levels drop, and biofilm builds up in pipes, jets, and filters.
Annual Cases and Fatality Rate
It is estimated that there are 4,000 to 6,000 cases of Legionnaires' disease in the UK each year, with a fatality rate of 7-12% among those infected. As climate change leads to warmer average temperatures and more frequent weather extremes, this risk is increasing. Hot tubs operate within the 25-45°C range that supports Legionella growth, and the potential for water spray heightens the risk if not properly managed.
Safety Advice from Experts
Greg Rankin, CEO at Hydrohawk, said: "As temperatures rise, it’s easy to get caught up in the excitement of barbecues and evenings outdoors. However, behind the scenes, Legionella remains a silent yet serious threat - especially in warm, stagnant water systems, such as unused hot tubs or spa pools. As climate change continues to create ideal conditions for Legionella bacterium to thrive, raising awareness and taking preventative steps has never been more critical."
He added: "Hot tubs, in particular, have grown significantly in popularity over recent years, so it’s vital that homeowners understand how to operate them safely, especially as they can provide ideal conditions for Legionella growth. When left unused for any length of time, the risk of Legionella infection increases significantly. Fortunately, there are some simple steps people can take to minimise that risk. Always ensure your hot tub has been treated with the correct chemicals at the appropriate levels before switching it on. Chlorine and bromine are the most commonly used disinfectants and can help keep the risk to a minimum. As part of this, a quick and easy Legionella test can help to detect potential risks early, so that you’re sure that water-borne illnesses won’t get in the way of your summer fun."
Preventative Measures
To reduce the risk of Legionella, hot tub owners should regularly test water quality, maintain proper disinfectant levels, and thoroughly clean and drain the system if it has been unused for a period. The warning comes as alerts for the heatwave remain in place until at least Thursday, with millions of households at risk.
