A third person who visited a downtown Chicago Marriott hotel has died after contracting Legionnaires' disease, Chicago city officials announced late Friday.

Officials with the Chicago Department of Public Health released test results Friday that showed that the primary source of the outbreak at the Marriott, located at 151 W. Adams St., was likely the spa and a decorative fountain in the main lobby. Samples taken from the fountain, the men's and women's locker rooms, and the spa's whirlpool all tested positive for the same type of Legionella found in the sick patients.

Marriott said it has removed the fountain and also closed parts of its luxury spa. The hotel claimed it is now working with a water safety consulting company to install cleaner water systems and, according to Dr. Kathleen Ritger, medical director over communicable disease at the CDPH, the hotel is now safe.

"We believe that there is no ongoing health threat at the hotel," she said. "Individuals who stayed at the hotel during this time period [July 6 to Aug. 15] who are experiencing flu-like symptoms are encouraged to get in touch with a healthcare provider because it is important that all potential cases are diagnosed and treated as soon as possible to shorten the recovery period and help prevent serious complications."

Ten people who stayed at the hotel during the month-long period have reported cases of Legionnaires' disease, including the three deaths. None of the confirmed cases were individuals living in Chicago.

Marriott believes some 8,500 people stayed at the hotel during the time frame in question and has contacted the majority of them to make them aware of the situation. A hotline set up by the CDPH, meanwhile, has received over 100 calls from people both reporting symptoms similar to Legionnaires' disease and also looking for general information.

Legionnaires' is a severe form of pneumonia that is contracted when one breathes small water droplets -- be them vapor or mist -- that are contaminated with the Legionella bacteria. Legionella bacteria is found in low levels in most waters, but can flourish and become lethal when water quality is not maintained.

Legionnaires', which derives its name from a 1976 outbreak at a convention of the American Legion, has an incubation period of up to two weeks after exposure and typically begins with a high fever, headache an chills, according to the CDPH. Two to three days later, patients develop pneumonia-like symptoms, such as a cough, chest pain or shortness of breath.

Each year between 8,000 and 18,000 people are infected with the disease in the U.S., according to the Centers for Disease Control and Prevention, and between 5 and 30 percent of the cases prove fatal. Most people exposed to Legionella do not become ill, while some come down with the non-fatal Pontiac Fever, which lasts for just two to five days.

A separate outbreak of Legionnaires' disease in Quebec City took its eleventh victim Sunday. City officials believe several cooling towers around the city are to blame, and at least 169 people have been infected since July.