What to Know A patient has contracted Legionnaires' disease at Mount Sinai Beth Israel Hospital, officials say

Legionella bacteria was discovered in the hospital's water after a routine testing

The hospital says it's put on special filters and the facility remains open and safe

A New York City hospital patient has contracted the potentially deadly Legionnaires disease, officials say.

The patient at Mount Sinai Beth Israel Hospital in Gramercy tested positive for the disease, which can lead to severe pneumonia, after routine testing of the hospital's water system last month showed Legionella bacteria in several areas of the hospital.

Last year, the city saw its worst Legionnaires outbreak, clustered in the Bronx, when 12 people died and more than 100 people were sickened. Some of them hospital patients, and those cases were blamed on cooling towers.

A Beth Israel worker said Wednesday night the contaminated water was in the building's plumbing system.

The hospital said it has put special filters on sinks, showerheads and ice machines, and has also implemented water restrictions. Officials insist it's not an outbreak and say "the hospital remains fully open and safe for patients and visitors."

The New York State Department of Health added in a statement, "The DOH has been working with Mt. Sinai Beth Israel to help ensure there is no further risk of Legionnaires' disease at the hospital."