2 new Legionnaires' cases reported, this time at U. of Chicago Medical Center

(Photo by Joshua Lott/Getty Images)

For the second time in a week, state health officials are investigating cases of Legionnaires’ disease in patients who may have been exposed at a Chicago hospital.

After two patients tested positive for the disease at the University of Chicago Medical Center, the Illinois and Chicago departments of public health visited the hospital this week to test the facility’s water to determine the source of the Legionella bacteria, officials said in a statement.

The investigation is limited to the hospital and there is no risk to the public, the state’s public health department said.

The two patients who tested positive for Legionnaires’ also were treated at other hospitals where they could have been exposed to the bacteria, officials said. State officials did not name the other facilities.

A spokesperson for the University of Chicago Medical Center said tests of the hospital’s water show no sign of the bacteria.

“We are confident all our patients are safe,” the spokesperson said in a statement. “To be clear, these patients were in our facilities for only a portion of their risk period, and none of our water tests has revealed Legionella.”

One week ago, two other cases of Legionnaires’ were reported at Mercy Hospital. A spokesperson for Mercy said the hospital “and its patients are safe,” and that tests have shown no bacteria in the hospital’s water system.

Representatives for both Mercy and the University of Chicago Medical Center said their facilities have followed water management guidelines from the Centers for Disease Control and support the ongoing investigation.

Legionella bacteria are transmitted through drops of water and can cause serious lung infections and possibly death. The bacteria mixes with the air in showers or fountains, and can cause illness when inhaled.

Incidents of Legionnaires’ disease have risen over 500 percent in the United States since 2001, according to the CDC. The disease was discovered in 1976 during an outbreak at a Philadelphia convention of the American Legion.