CHICAGO (CBS) — A day after his office announced he has taken a leave of absence due to “exhaustion,” it’s still unclear when U.S. Rep. Jesse Jackson Jr. will return to work.

CBS 2’s Jim Williams reports people around the congressman said he’s facing a serious health challenge, and that’s been underscored by his recent actions – or, rather, his inaction in Congress.

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No one at Jackson’s office at 71st Street and Exchange Avenue would talk on camera on Tuesday. On the phone, however, staffers said they don’t know where Jackson is, and noted the Jackson family has asked for privacy after announcing he’s been on medical leave since June 10 to deal with exhaustion.

Jackson’s chief of staff, Rick Bryant, told WBBM Newsradio Political Editor Craig Dellimore that the family doesn’t want Jackson’s staff to say where the congressman is, and he said he doesn’t know what caused Jackson’s exhaustion, or when Jackson will return to work.

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Jackson has missed dozens of votes on Capitol Hill recently, but Bryant said he still has an exemplary voting record.

A close associate of the Congressman’s offered this analysis: “People expect him to resolve his situation, his health. His health is more important than a vote (in Congress).”

Political Consultant Delmarie Cobb – who worked on Jackson’s first campaign for Congress 17 years ago – said that tells her the issue is serious.

“I think he went five years without missing a vote, and for him to miss almost 30 votes in this month, that’s very significant,” she said.

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Jackson has been under enormous pressure in recent years: his name has been linked to the U.S. Senate seat scandal that took down former Gov. Rod Blagojevich, he’s facing a House Ethics Committee investigation, he has been dealing with marital problems over his affair with a restaurant hostess, and a key Jackson fundraiser was indicted last week.

That fundraiser, Raghuveer Nayak, was a key figure in the Senate seat scandal, and is also at the center of the Ethics Committee probe. Nayak allegedly offered to raise up to $6 million in campaign cash for Blagojevich to appoint Jackson to President Barack Obama’s old Senate seat. Jackson has denied directing Nayak to offer campaign cash for the seat, or any knowledge of such a deal.

Bryant insisted Nayak’s arrest on racketeering, fraud, and tax evasion charges was not connected to Jackson’s leave of absence. He said the congressman had planned an announcement earlier, but delayed it after news of Nayak’s arrest.

Dr. Jennifer Earvolino, a physician at Rush University Medical Center, said she takes any patient’s claims of exhaustion very seriously. She first looks first to rule out a physical cause. Often, though, she said stress is to blame.

“Sometimes maybe it is just a need to step back, and kind of re-evaluate, and take some time off, and just get things back in order,” Earvolino said.

Jackson’s staff said they don’t know when he might get back to work.

Cobb said she would advise Jackson to be up front about what he’s going through, and tell his constituents “I’m still here. I’m still going to be effective. I’m not going to retreat. I’m not going to hide. … Up until the end, I’m going to fight for my name, and I’m going to fight for you, my constituents.”

That might not happen any time soon. Patrons at what’s said to be Jackson’s favorite breakfast spot in his Congressional district said it’s been quite a while since he’s been there.

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Although it’s only been a day since Jackson announced he’s suffering from exhaustion and has been on medical leave, House Minority Whip U.S. Rep. Steny Hoyer (D-MD) said he was first told of the situation last Friday.