Cases of Legionnaires’ Disease in Michigan Increased by 569% Since 2020

In the first two weeks of July, 107 cases of Legionnaires’ disease have been reported in 25 counties in Michigan, an increase of 569% from the 16 cases reported during the same period in 2020, according to the Michigan Department of Health and Human Services (MDHHS).

The state has not been able to identify any common sources of the infection. Fortunately, the 107 cases identified in early July have not led to any deaths.

The MDHHS is coordinating with local health departments across the state to investigate the reason behind the recent increase. Officials point to intense summer weather as a possible explanation. Legionella bacteria survive better in the heat of the summer and early fall and in stagnant water.

“Recent weather trends including rain, flooding, and warmer weather may be playing a role in the rise of reported legionellosis cases this summer,” said Dr. Joneigh Khaldun, MDHHS chief medical executive and chief deputy director for health.

Health experts also believe the increase in Legionnaires’ disease cases may be linked to facilities reopening after being closed during the first year of the pandemic, The Detroit News reports. Legionella bacteria are found naturally in freshwater lakes and streams but can also be found in man-made water systems. Potable water systems, cooling towers, whirlpool spas, and decorative fountains offer common environments for legionella bacteria growth and transmission if they are not cleaned and maintained properly. Warm water, stagnation, and low disinfectant levels support bacterial growth in these water systems.

“These big office buildings that weren’t used often in the pandemic season—there’s a lot of stagnant water in the pipes,” said Chuanwu Xi, a professor of environmental health sciences and global public health at the University of Michigan School of Public Health. 

Ensure your facility’s water system isn’t harboring dangerous pathogens as building residents return. Learn best practices for effective water management and about tools that can alert you to water system problems to prevent an outbreak of Legionnaires’ disease in your facility.