Increase in Legionnaires' Disease Cases in Southeast Michigan

Contact: Jennifer Eisner 517-241-2112

For Immediate Release: August 4, 2017

LANSING, Mich. – The Michigan Department of Health and Human Services (MDHHS) is coordinating with local health departments from the City of Detroit and Macomb, Wayne, and Oakland Counties to investigate an increase in the number of cases of legionellosis in southeast Michigan this summer.  In June and July of 2017, 73 cases were identified in this region—a 143 percent increase (30 cases) from the average total cases in these same two months from 2014-2016.  While legionellosis is most common in the summer and early fall, this increase is higher than expected for southeast Michigan for this time of year.  To date, no common source of infection has been identified.

The MDHHS and the local health departments are working to inform providers in southeast Michigan of the increase in cases and share information regarding testing and treatment.  Legionellosis is a respiratory infection caused by Legionella bacteria.  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. 

Legionella bacteria are found naturally in fresh water 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.  Transmission to people occurs when mist or vapor containing the bacteria is inhaled.  Legionellosis does not spread from one person to another. Risk factors for exposure to Legionella bacteria include:

  • Recent travel with an overnight stay outside of the home

  • 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

Individuals with any concerns about Legionnaires’ disease should talk to their physician.  The MDHHS and local health departments will continue to monitor cases and provide updates to the public.  More information on Legionella and Legionnaires’ disease can be found on the Centers for Disease Control and Prevention website: https://www.cdc.gov/legionella/index.html.

# # #