Sen. Johnny Isakson (R-Ga.) says doctors have blamed his sudden illness last month on a "toxic shock" but still don't know further details.

Isakson, 65, was rushed to an Atlanta hospital on the morning of March 23 and released after three days before being readmitted on March 29 after doctors found a blood clot in his leg. The hospitalizations forced Isakson to miss the Senate's dramatic vote last month on a healthcare reform reconciliation bill.

Strolling the halls of the Senate this week, Isakson said doctors are still stumped about the source of the bacterial infection that made him ill.

"It was a toxic shock to something they still don't know. The lab work's up and they're studying it now, but they just don't know," Isakson said. "The doctors got it fixed, but it was apparently just a toxic shock reaction to bacteria."