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Michigan alerts residents to be aware of legionellosis

The Michigan Department of Health and Human Services (MDHHS) is reminding residents to be aware of legionellosis, a respiratory infection caused by Legionella bacteria. Legionellosis can present as Legionnaires’ disease with symptoms of fever, cough, shortness of breath and pneumonia; or Pontiac fever with similar symptoms but no pneumonia. Legionellosis is most common in the summer and early fall when warm, stagnant water can allow Legionella bacteria to grow in water systems. Water systems in large buildings, cooling towers, whirlpool spas and decorative fountains offer common environments for bacterial growth, and transmission occurs if they are not cleaned and maintained properly. 

Transmission of Legionella bacteria to people primarily occurs when water mist or vapor containing the bacteria is inhaled. Less commonly, people with difficulty swallowing can get sick if water containing the bacteria accidentally goes into the lungs while they are drinking. Legionellosis does not generally spread person to person. Risk factors for exposure to Legionella bacteria include:

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

“If you are at risk and may have been exposed to Legionella it is important to monitor your symptoms and contact your health care provider if you become ill,” said Dr. Natasha Bagdasarian, MDHHS chief medical executive. “Legionnaires disease is treatable with antibiotics and health care providers are required to report cases to the health department.”

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

  • People over age 50.
  • Current or former smokers.
  • People with chronic lung disease.
  • People with weakened immune systems from diseases or certain medications.
  • People with chronic health conditions such as cancer, diabetes, or liver or kidney failure.

In 2023, 186 confirmed legionellosis cases have been reported in Michigan through the end of July, compared to 196 cases in 2022. This year’s cases are lower than the previous five-year (2018-2022) average of 234 confirmed legionellosis cases for the same time period of January through July. MDHHS and local health departments will continue to monitor cases. Individuals with concerns about Legionnaires’ disease or exposure to the Legionella bacteria should talk to their health care provider.



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