Since then, detections have steadily increased, rising to 3% in 2023 and 5% in both 2024 and 2025.
So what’s changed?
During the COVID-19 pandemic, building’s water systems weren’t functioning as usual and the management of such became a key focus. With offices, school and public buildings sitting empty or partially used, there was a strong focus on flushing regimes, temperature checks and risk assessments to prevent stagnation and bacterial growth.
Fast forward to today, and most buildings are back to full occupancy. But with ‘normal’ operations restored, it’s possible that vigilance has slipped. Routine control measures may not be getting the same attention they did when empty buildings were a major concern. It is also important to note that flexible working is now the norm, so building occupancy is more variable than ever and demand on the water systems will fluctuate.
Interestingly, national health data doesn’t show the same upward trend. UK Health Security Agency figures indicate that Legionnaires’ disease cases actually fell in 2024 compared to 2023, returning to levels seen earlier in the decade. In other words, more Legionella is being detected in our water systems, but this hasn’t translated into more people becoming ill.
That doesn’t mean the risk has gone away. There is a key takeaway for building managers: Don’t let ‘business as usual’ turn into complacency. Regular monitoring, maintenance, temperature control and risk assessments still matter, even when buildings are busy appear to be running smoothly.