Legionnaires’ disease outbreak - US

Kerry Clarkson
Senior Consultant
16th February 2024

This could be cooling towers systems on the roof of a building, or poorly managed domestic water services, allowing colonisation of legionella bacteria to be transmitted from the showers.

In 2023, there was an outbreak in Grand Rapids, Minnesota with 14 cases confirmed and over 130 people ill. It is believed there have been no deaths directly related to this recent incident, though media reports vary. This outbreak has been traced back to the local water supply, with several buildings in the community testing positive for the same strains of Legionella bacteria as identified in the infected individuals.

Unlike the UK, where all our water is routinely chlorinated by the supply companies long before it reaches our taps, Grand Rapids does not chlorinate its water. While this would generally be an effective measure to help remove the bacterial contamination, there could be unintended consequences for a system that has not been designed to tolerate the required chlorine levels. Additional water sampling is planned, and the results will be used to inform what action will be taken.

According to the Centres for Disease Control, the US has approximately 10,000 cases of Legionnaires’ disease reported annually. Proportionally, this is higher than the UK, where we tend to have a stricter approach to managing our water systems. There are very tight control measures for our water supply companies that dictate the quality of the water entering our buildings.

However, it is the responsibility of those in control of the buildings to safely manage the water services inside it and it is imperative this is done to prevent the growth of legionella bacterial in the system.

A key control measures to do this is maintaining the correct temperatures; hot water should be supplied between 50°C and 60°C and cold supplied below 20°C. It is vital that there is good movement of water through a system, and this may need to be artificially created through a flushing regime if a building has low occupancy. Finally, making sure the system itself remains in a good, clean condition with storage tanks and hot water units regularly inspected and the correct materials used. If yon need any help with your legionella management, please get in touch.