Experts are warning of a deadly disease you can catch in your own garden that could spike in the UK this week during the 38°C heatwave, with alerts in place until at least Thursday. The risk of Legionnaires' disease—a potentially fatal lung infection caused by inhaling droplets of water containing Legionella bacteria—increases during hot weather, particularly in stagnant or untreated water systems.
Millions of Hot Tubs at Risk
According to new research, one in ten Brits now own a hot tub or jacuzzi, meaning there are almost 3 million now in operation across the country. A further one in ten have a swimming pool or cold plunge bath. More than half of owners say they are not fully confident that their cleaning and maintenance routines are robust enough. Among those, 28% admit they have not considered or would rather not think about hygiene risks and associated germs.
92% do not regularly test for Legionella, despite the potentially serious health consequences. Hydrohawk, the UK's leading Legionella authority, has provided advice on how to stay safe as households enjoy the rising temperatures.
Expert Warnings
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.”
It is estimated that there are 4,000-6,000 cases of Legionnaires' disease in the UK each year, killing between 7-12% of all those infected. As the UK experiences warmer average temperatures and more frequent weather extremes due to climate change, this risk is increasing.
How Hot Tubs Become Dangerous
Hot tubs operate in the same temperature range that supports Legionella growth (roughly 25-45°C). That, and the scope for water spray, can increase the risk of Legionella if not properly managed. Intermittent use—particularly during fluctuating hot and wet spells like recently experienced in the UK—remains a particularly critical safety concern. When a hot tub sits unused, water often stagnates in the plumbing and fittings, disinfectant levels fall away, and biofilm can build up on pipes, jets, and filters, creating the perfect conditions for Legionella bacteria to thrive. When reusing for the first time in a while, it is therefore vital to ensure a thorough clean, drain, and disinfection of the entire system before anyone gets in.
Simple Steps to Stay Safe
Greg Rankin, CEO at Hydrosense, said: “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.”
