Legionella and hot weather hazards
It is now 40 years since the first outbreak of Legionnaires’ disease in a Philadelphia hotel in summer 1976, when over 200 people were infected and more than 30 patients died. Cases of Legionnaires’ disease always spike during the warmer months so now that summer has finally arrived we thought it would be worth looking at the reasons behind this and offering some hot weather advice on the control of Legionella.
Figures from Public Health England show that in 2013, more than a fifth of all cases (21.8%) reported the onset of symptoms during August. According to the Microbiology Society, “Legionnaires’ disease outbreaks are most likely in the summer months between July and September when the weather is warmer and more humid.” There are various reasons for this, including the increased use of air conditioning, but a major factor is that Legionella bacteria thrives at temperatures over 20°C so during hot weather the incoming mains water may be in this danger zone.
Temperature is one of the most important control measures for reducing the risk of Legionella. Keeping your cold water below 20°C and your hot water at over 50°C will prevent the bacteria from flourishing. Ensure that water tanks and pipes are lagged and not in direct sunlight to help regulate the water temperature. Similarly, in the garden don’t use water that has warmed up in the hosepipe or other receptacles; flush or clean them out thoroughly first. During hot weather it’s a good idea to check water temperatures regularly and if a property is left empty for a period of time (due to residents being on holiday), the system should be flushed and taps run for several minutes to expel any stagnant water.
Another reason for the summer spike in Legionnaires’ disease cases is the growth in foreign travel. Between 30% and 40% of cases in the UK are ‘travel-associated’, indicating that holidaying abroad is an additional risk factor. Just as the first outbreak of the disease happened at a hotel, it is still the case that hotels and leisure complexes are often implicated in cases of Legionnaires’. They are more likely to have complex water systems, including air conditioning cooling towers and multiple water storage tanks. Other high risk areas include swimming pools, spa pools and steam rooms, all of which are visited more often when on holiday.
It’s also worth noting that owners of holiday cottages and Airbnb hosts are bound by the same health and safety legislation in the UK as residential landlords. Don’t be afraid to ask about the control of Legionella when you book your stay and report any concerns you have about water hygiene at the property.
Our message to you is enjoy your summer and make the most of the hot weather, but be aware of water cleanliness and the potential harm which can be caused by invisible bacteria.