The Michigan Department of Health and Human Services (MDHHS) is coordinating with local health departments across the state to investigate a recent increase in reports of Legionnaires’ disease. Between July 1 and July 14, 107 cases of Legionnaires’ disease have been reported in 25 counties. While increases in cases are often related to environmental factors, including heat and rainfall, this represents a 569% increase from referrals from the same period in 2020 (16 cases) and a 161% increase from referrals from the same period in 2019 (41 cases). Confirmed cases include 19 in Wayne County, 17 in Oakland County and 17 in the City of Detroit and 15 in Macomb County. MDHHS and local health departments are working to inform healthcare providers of the increase in cases and share information regarding testing and treatment. While legionellosis cases are most common in the summer and early fall when warming, stagnant waters present the best environment for bacterial growth in water systems, this increase is higher than expected for Michigan for this time of year. MDHHS is requesting that providers keep this in mind with patients that present for care with pneumonia and existing risk factors for this infection. To date, no common sources of infection have been identified.
