Doctors released U.S. Rep. Joe Wilson from the hospital on Saturday, but the congressman remains weak and the illness remains a mystery.

Wilson suffered from a viral illness that stumped doctors, said his son, S.C. Attorney General Alan Wilson said Monday as he endorsed former Gov. Jon Huntsman for the Republican 2012 nomination for president.

"I checked on him yesterday at the house," Alan Wilson said. "He's up and he's walking around. He's still weak but he's getting better everyday and it's just a process.

"It was viral and it is not contagious and it is not lethal, so he's going to be fine."

Rep. Wilson spoke from his hospital bed on Friday and said he expected to be well enough to make his annual district bus tour, which was rescheduled to Sept. 26-30 because of the illness.

Last week, Joe Wilson's staff released a statement from Lexington Medical Center staffers, saying that Wilson would likely recover from the illness.

"While the exact infection agent has not yet been defined, there is no evidence of serious complication and complete recovery is expected," the statement said.