Democratic leaders joined colleagues and constituents Wednesday in calling for Jackson Jr. to offer a public explanation as soon as possible.
Congressman Jackson started his leave on June 10, but he waited two weeks to make it public.
The mystery surrounding Jesse Jackson Jr.'s illness could not have happened at a worse time for his father. The veteran civil rights leader is hosting the annual Rainbow PUSH coalition conference in Chicago.
For the first time in the Rainbow PUSH convention's 41 years, Rev. Jesse Jackson tried to avoid cameras and reporters. He apparently did not want to hear questions about his son, Rep. Jesse Jackson Jr., who has taken an extended leave from Congress without explaining the nature of his illness.
As Jackson Sr. tried to leave the Rainbow PUSH luncheon through the ballroom kitchen Wednesday afternoon, ABC7 intercepted him to ask about the non-stop rumors surrounding his son's health.
"I should not have to dignify rumors," said Rev. Jackson. "It's not fair. His medical treatment is a private matter by his doctors, his family. At the appropriate time you will hear as you should."
Meanwhile, in Washington, House Minority Whip Steny Hoyer urged Jackson, who stands for re-election in November, to provide voters more detailed information.
"I think Congressman Jackson and his office and his family would be well advised to advise the constituents of his condition," Hoyer said. "He's obviously facing a health problem."
But Democratic minority leader Nancy Pelosi advised patience.
"Our prayers are with his family. The timing is not related to our curiosity but his healthcare needs," said Pelosi.
The congressman's wife, Alderman Sandi Jackson, told the Chicago Tribune Wednesday she was "hopeful" doctors would release details of the congressman's condition "soon". She claimed to be in constant contact with her husband's medical team.
"I'm asking the media, I'm asking the Democrats to back off of this young man," said former Illinois U.S. Senator Roland Burris.
Burris said his fellow Democrats should end their calls for Jackson to come forward and blamed the news media for trying to bring down the congressman.
"The media's driving it," said Burris. "They drove the mess with me."
The Rainbow PUSH conference continues through Saturday.
Congressman Jesse Jackson's Jr.'s office has released little information about his condition, which requires treatment and a medical leave from Congress.
This is a prime example of how the laws Congress writes for us sometimes don't apply to the lawmakers themselves. ABC7 research found Congressman Jackson has not followed some of the past practices of members of Congress who miss work, but a spokesman for what amounts to the House's HR department says there are no written rules regarding medical leave.
Congressman Jackson has missed nearly 80 votes in the past month. Despite the absence, Jackson continues to receive his full $174,000-a-year salary. That amounts to $14,500 since his mysterious medical leave began.
When Senator Mark Kirk suffered a stroke, doctors publicly updated his condition. That hasn't been the case for Jackson.
"Nine times out of 10, the speculation is much worse than what he's actually dealing with," said Eric Herman.
Herman is a former journalist who now works in crisis communications. He says the secrecy shrouding Jackson's condition does more harm than help.
"They get sickness, they get illness. They are people. There is compassion. What they don't like is being manipulated," said Herman.
On Capitol Hill, many congressmen make a point of entering the reason for missing votes into the official record.
Congressional rules don't require a doctor's note or reduced wages. They also don't say how long is too long for a representative like Jackson to be out.
"Congress does have a much more generous policy than most employees enjoy with their employer," said Jon Goldman.
Goldman is an employment law attorney who points out Congress's perks are far beyond those established by the Family and Medical Leave Act.
"They would have to provide medical documentation supporting a serious health condition before they can take a leave, and even then it's an unpaid leave," Goldman said.
Mark Allen has known Congressman Jackson since the two were kids. He is disappointed many of Jackson's fellow Democrats are questioning his illness.
"For them, Illinois representatives, to not have his back-- give the man some peace. I'm very disturbed by this," said Allen.
House minority leader Nancy Pelosi's staff says she was told of Jackson's medical leave, but he did not submit a formal letter explaining it. They say he doesn't have to.
The bottom line: There are very few rules governing members of Congress who miss work.