MDHHS Investigating Recent Increase in Legionnaires’ Disease in Michigan

The Michigan Department of Health and Human Services announced Monday that it is working with local health departments across the state to investigate a recent increase in reports of Legionnaires’ disease.

Confirmed cases include 19 in Wayne County, 17 in Oakland County and in the City of Detroit and 15 in Macomb County.

Legionella bacteria causes two forms of legionellosis respiratory infections. Legionnaires’ disease is an infection with symptoms that include fever, cough and pneumonia. A milder form of legionellosis, Pontiac fever, is an influenza-like illness without pneumonia that resolves on its own.

“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, in a statement. “We want everyone to be aware of Legionnaire’s disease, especially if they may be at higher risk for illness and we ask that healthcare providers remain vigilant, and test and treat appropriately.”

Transmission to people occurs when mist or vapor containing the bacteria is inhaled. Legionnaires’ disease does not spread person to person. Risk factors for exposure to Legionella bacteria include:

  • Recent travel with an overnight stay.
  • Recent stay in a healthcare facility.
  • Exposure to hot tubs.
  • Exposure to settings where the plumbing has had recent repairs or maintenance work.

Most healthy individuals do not become infected after exposure to Legionella. Individuals at a higher risk of getting sick include the following:

  • People over age 50.
  • Current or former smokers.
  • People with chronic lung disease.
  • People with weakened immune systems from diseases, such as cancer, diabetes or liver or kidney failure.
  • People who take immunosuppressant drugs.

As many buildings are currently reopening after extended COVID-19 closures or periods of limited use, this may also create an environment for potential amplification and transmission of Legionella bacteria. 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 bacterial growth and transmission if they are not cleaned and maintained properly. Warm water, stagnation and low disinfectant levels are conditions that support growth in these water systems.