Cases of legionellosis in Michigan are trending higher in 2018 than they were in 2017.

The Michigan Department of Health and Human Services reports that as of yesterday, there have been 135 confirmed cases of legionellosis in 33 counties in Michigan in 2018. That's compared to 107 confirmed cases by the same date in 2017.

Legionellosis is a respiratory infection caused by legionella bacteria. The bacteria can cause Legionnaires’ disease, which is an infection with symptoms including fever, cough and pneumonia. The bacteria can also cause a milder form of legionellosis, Pontiac fever, which is an influenza-like illness without pneumonia.

The CDC says, "Most people exposed to legionella do not get sick. However, people 50 years or older, current or former smokers, and people with a weakened immune system or chronic disease are at increased risk."

Confirmed cases in Michigan in 2018 include 24 in Detroit, 19 in Macomb County, 16 in Oakland County, 11 in Wayne County and 10 in Genesee County. 24 cases have been confirmed since July 1 with another 13 cases waiting for confirmation.

The increase is being seen nationwide.

Legionella bacteria are found naturally in fresh water lakes and streams but can also be found in man-made water systems including water towers, hot tubs and decorative fountains. Transmission to people occurs when infected mist or vapor is inhaled.