Story highlights Clinton has been sidelined for three weeks

She had stomach flu, and suffered a concussion when she fainted

Clinton has promised to testify next month before congressional committees

The committees are focusing on the attack on the US diplomatic office in Benghazi, Libya

Secretary of State Hillary Clinton will return to work next week after a nasty bout with stomach flu and a concussion sidelined her for three weeks.

"The Secretary continues to recuperate at home. She had long planned to take this holiday week off, so she had no work schedule," her spokesman, Deputy Assistant Secretary Philippe Reines said in a statement. "She looks forward to getting back to the office next week and resuming her schedule."

Clinton spent the holidays with her family after working from home for the past week. Clinton's doctors, in a statement released last weekend, said they told her to cancel all work events and "rest and avoid any strenuous activity."

Clinton was recovering from the stomach flu when she fainted and suffered a concussion.

Her doctors have grounded her from overseas travel for several more weeks, but her return to the State Department paves the way for her to testify before Congress on the September 11 attack on the U.S. diplomatic office in Benghazi, Libya.

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Last week Clinton's deputies Thomas Nides and Bill Burns testified in her place at open hearings on the deadly attacks after Clinton had to bow out under doctors' orders. That did not sit well with some members of Congress, especially Republicans, who have been highly critical of the Obama administration's handling of the Libya attack and who have called for Clinton to appear when she returns to work.

Clinton has promised to testify her next month before the before the Senate Foreign Relations and House Foreign Affairs committees about the findings of a scathing independent report that found "grossly inadequate security" and "systemic failures and leadership and management deficiencies" at the State Department. Clinton said in letters to the heads of those committees that she accepted every one of its recommendations, including strengthening security, adding fire-safety precautions and improving intelligence collection in high-threat areas.

One official has resigned and three more have been disciplined in the wake of the report.