State and local health officials are investigating an increase in the number of cases of legionellosis in southeast Michigan (the City of Detroit and Macomb, Wayne, and Oakland Counties) 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 Michigan Department of Health and Human Services (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.
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