A fourth case of Legionnaires' disease has been confirmed and a fifth is suspected at Selfridge Air National Guard Base in Harrison Township.

John Ambrose, an epidemiologist with the U.S. Army Public Health Command, said Monday three of the confirmed cases involve employees from Warren-based TACOM Life Cycle Management Command. One is from the 127th Wing, Michigan Air National Guard.

The fifth person also is from TACOM.

Brig. Gen. Michael Peplinski, commander of the 127th Wing, said one person remained hospitalized in critical condition. A bacterial outbreak in July sickened more than 30 people.

Legionnaires' disease is a type of pneumonia caused by bacteria. You usually get it by breathing in mist from water that contains the bacteria, the Centers for Disease Control and Prevention said on its website.

The disease, which takes its name from an outbreak at the Pennsylvania American Legion convention in Philadelphia in 1976, can be life-threatening, but most people recover with antibiotic treatment.

The Associated Press contributed to this report.