That's the word from WTMJTV in Milwaukee. The station reports that four people have been confirmed to have the disease.
All four were infected in mid or late July. Officials learned about the cases Wednesday when lab results were returned.
The patients were all middle-aged or elderly, and all were hospitalized. Milwaukee health officials are investigating whether the four cases are related.
Officials say all four are recovering.
Legionnaires' disease is caused by a bacterium that grows in warm, stagnant water. An estimated 8,000 to 18,000people in the U.S. get the disease each year. About 5 percent to 30 percent of people who get the disease die.
Legionnaires' disease can't pass from person to person.