A cluster of 14 cases of Legionnaires’ disease in Grand Rapids, Minn., was traced to the municipal water supply, a state health investigation found.
City officials announced Monday that they plan to flush and disinfect the water system to reduce the risk of illness, caused by inhaling water droplets containing Legionella bacteria. The disease is fatal in 1 in 10 cases. Although no one has died in this epidemic, 11 people have been hospitalized.
Thirteen infected people were in two buildings in a small area of Grand Rapids, while the 14th was nearby, said Trisha Robinson, supervising epidemiologist with the Minnesota Department of Health’s waterborne disease unit. Genomic sequencing of the patients’ lab samples linked their infections to the same bacterial strain.
Investigators looked for other possible sources, but exposure to the city’s water supply was the only risk factor all 14 people had in common, she said.
Infections rarely occur through drinking water. This usually happens when people inhale water droplets from a shower, faucet, spray bottle or pressure washer, she said. People are not at risk if they drink water in Grand Rapids, but should use distilled or filtered water for aerosol devices such as CPAP machines.
The state began investigating shortly after the first cases were identified in Grand Rapids in April. Although Legionnaires’ disease is more common in warmer months, cases of this outbreak have occurred sporadically throughout 2023 and include two illnesses in 2024.
Legionella tends to grow and spread in stagnant, warmer water, especially if not treated with chemicals such as chlorine. Grand Rapids operates one of Minnesota’s few community water systems without chlorination, which is allowed for community wells that tap groundwater, according to the state Department of Health.
While a chlorination system is now “under consideration” as a strategy to deal with the outbreak, it can be difficult to introduce the disinfectant into a previously unchlorinated system, said Julie Kennedy, chief executive of Grand Rapids Public Utilities. “Our approach must be methodical to ensure we avoid any additional health, safety or distribution system complications. We will provide local updates and customer advisories as this situation evolves. plan.”
Minnesota reported 134 Legionnaires’ cases and six deaths in 2023, most of which occurred in isolation and did not trigger state investigations. The Grand Rapids outbreak is major for Minnesota, but it’s not the largest, Robinson said. More than 20 Legionnaires’ cases and one death were linked to a beverage plant’s cooling towers in Hopkins in 2016.
The risks of health problems from Legionnaires’ disease are high for people who are 50 years or older, smoke, and have chronic health problems. The Department of Health urged doctors in Grand Rapids to watch for suspicious symptoms and for patients to seek medical attention if they develop pneumonia — which could indicate Legionnaires’.
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