The Chicago Department of Public Health now reports it has received eight confirmed cases of Legionnaires including the two deaths.
Of the eight, one is from Illinois. The rest are from out of state. They have not been identified.
Because Legionnaire's disease, which is a severe form on pneumonia, is contracted by breathing in infected water, the JW Marriot has drained its pool, whirlpool, lobby fountain and indefinitely closed parts of its spa.
"We have instructed them to notify all the guests between July 16 and August 15, which we feel is the period with most risk, and have been working with the Illinois Department of Public Health to look at the water systems at the hotel and have them evaluated," said Dr. Kathy Riger, Chicago Department of Public Health.
The health department says it does not believe there is an ongoing health threat.
"It's certainly possible that a normal, healthy person could contract Legionnaire's disease," said Dr. Stacy Raviv, NorthShore University Health Care System. "You're more likely to contract it in the first place if you have underlying lung disease, if you're a smoker or if you're older."
Marriott says they have been cooperating with health officials and the hotel remains open.
JW Marriot spokesperson Jeff Flaherty told ABC7, "we believe the hotel is safe and our doors are open for business. We have retained an expert consultant with whom we have developed a comprehensive plan, in conjunction with the Chicago Department of Public Health and the Illinois Department of Health, to prevent this from happening again in the future."