University of Wisconson Health's University Hospital in Madison identified four patients who have developed Legionnaires' disease. These are the first cases of the disease acquired at the hospital in 23 years.
The hospital urine-tested the patients, three of whom were previously hospitalized and one of whom is an inpatient. All four tested positive for Legionnaires' disease in the past 10 days.
The hospital suspects the cause is its hot water system. Legionnaires', a type of pneumonia, is caused by bacteria that are usually present at low concentrations in tap water. People contract Legionnaires' when they inhale droplets of water in the air that contain the Legionella bacteria, according to the CDC.
The hospital has a water treatment system, however, "a recent adjustment to that system may have compromised its function," according to a statement.
University Hospital has stopped the use of hospital showers until early Nov. 29. Additionally, it is using a hyperchlorination process to flush all hot water lines to eliminate any Legionella bacteria.
Two of patients have been discharged, while the other two remain hospitalized. The Wisconsin state Division of Public Health has been notified.
Editor's note: The headline of this article was updated to "4 sickened with Legionnaires' disease at U of Wisconsin's University Hospital" at 10:30 a.m. on Nov. 30.