A jail inmate has been diagnosed with Legionnaires' disease, though health officials don't believe the case is related to an outbreak in the South Bronx that has killed 12 people and sickened more than 100 others, officials said Tuesday.

It was unclear how the unnamed 63-year-old Rikers Island jail complex inmate, who had underlying health conditions, contracted the disease, but a City Hall spokeswoman said all six of the Department of Correction's cooling towers had been disinfected last month and would be cleaned again.

The disease is caused when water contaminated with a certain bacteria is inhaled into the lungs. It's easily diagnosed and treated with antibiotics, and it poses the most risk to people who have underlying medical conditions.

Correction officials, City Hall spokeswoman Monica Klein said, have consulted with the Department of Health "and taken precautions to minimize the risks associated with this form of bacteria."

A teletype order that went out to correction officers Tuesday said no jails other than the one where the inmate was being held appeared to be affected and officials were cleaning the towers and shower heads "out of an abundance of caution."

The inmate had been housed at Rikers' largest jail facility for about seven months and was taken to a hospital over the weekend with pneumonia-like symptoms, testing positive Monday for the legionella bacteria, according to a city official not authorized to publicly discuss the case who spoke on the condition of anonymity.

Legionnaires' disease had not been detected for a few years at Rikers after a copper-silver ionization system was installed to disinfect the water system at one of the 10 jail facilities where the bacteria had been found, resulting in "quite a few" cases every year, the official said.

Between 8,000 and 18,000 people are hospitalized annually in the U.S. with the disease, studies have estimated, though many more cases go unnoticed because doctors don't commonly test for it and the symptoms appear so similar to other kinds of pneumonia.

In New York, health officials estimate 200 to 250 cases occur every year, though the current outbreak in the city's poorest neighborhood has become a significant public health issue because the numbers are elevated. Officials have said there were no new diagnoses there since Aug. 3.

People don't get sick by drinking contaminated water but instead when condensation is inhaled into the lungs. That's why officials have sought to test HVAC systems, cooling towers and air conditioning units.

Mayor Bill de Blasio and Gov. Andrew Cuomo, whose administrations have clashed over how to respond to the outbreak, put out a joint statement Tuesday with the City Council speaker to say they'd work together on legislation mandating the regulation of cooling towers.

Correction officers' union president Norman Seabrook, who sent out a press release announcing the Legionnaires' diagnosis, called for testing at all 15 Department of Correction facilities citywide.

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Associated Press writer David B. Caruso contributed to this report.