Chicago Teachers Union President Karen Lewis in Bad Health

Chicago Teachers Union President Karen Lewis underwent surgery on Wednesday and "has a serious illness," said union Vice President Jesse Sharkey, who at a news conference Thursday offered no further details on Lewis' health. Sharkey said he is taking over Lewis' duties at the union.

The continued lack of information on Lewis' health figures to only raise more questions about Lewis' potential bid to challenge Mayor Rahm Emanuel in the Feb. 24 election.

"I understand that many people in this room, and many people in this city, want to know about Karen Lewis' health status because they care about the mayoral election in this city," Sharkey said. "I think that's fair enough. But please be aware that's a question that I can't answer."

The news conference followed days of speculation on what's wrong with Lewis, 61, who was hospitalized Sunday night after becoming ill at her South Side home. Until Thursday, there was no official word on her condition or even what hospital she was at.