Officials said last week three people had contracted the disease after staying at the downtown hotel, and Monday they increased that number to eight, including the two deaths, the Chicago Sun-Times reported.
The hotel's pool, hot tub and fountain were drained after the outbreak was confirmed Aug. 14, Marriott spokesman Jeff Flaherty told the newspaper.
Health officials urged any guests who had stayed at the hotel between July 16 and Aug. 15 and were experiencing symptoms consistent with pneumonia to consult a doctor immediately.
More information is available through the Chicago Department of Public Health's hotline at (312) 746-4835.
Chicago sees about 30 cases of Legionnaires' disease each year, the newspaper said.