UPDATE: 6 confirmed cases of Legionnaires disease in Madison including one death

Updated 10:30 p.m. on November 29, 2918

UPDATE: MADISON, Wis. (CBS 58) -- There's now a total of six cases of Legionnaires' disease in Madison. One patient has died.

UW Hospital says the patient died on Wednesday night.

Three others are still being treated at the hospital.

A Madison newspaper also reported that St. Mary's Hospital is also treating one patient.

Legionnaires' disease is a severe form of pneumonia.

The source of the outbreak has not been identified at either hospital.

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MADISON, Wis. (AP) — Officials at UW Hospital say four hospital patients have developed Legionnaires' disease.

The patients tested positive for the disease in the past 10 days. The hospital is conducting tests to determine if the bacterium is related to the hospital's water system.

Legionnaires' disease is caused by bacteria typically present at low concentrations in tap water. UW Hospital uses a water treatment system designed to keep levels low, but officials say a recent adjustment to that system may have compromised its function.

UW Hospital says the risk comes only from hot water in the form of airborne droplets, such as water from a hot shower. Cold tap water poses no risk.

The Wisconsin State Journal reports officials have stopped all use of hospital showers. That is expected to continue until Thursday.