WASHINGTON » Secretary of State Hillary Rodham Clinton returned to work on today, after a month-long absence caused first by a stomach virus, then a fall and a concussion and finally a brief hospitalization for a blot clot near her brain.

Clinton presided over a senior staff meeting, the first she has convened since early December before contracting the stomach bug after returning from a trip to Europe on Dec. 7.

The illness forced her to cancel a planned visit to North Africa and the Middle East and left her severely dehydrated. While at home, she fainted, fell and suffered a concussion that was diagnosed by doctors on Dec. 20. During a follow up exam on Dec. 30, doctors discovered a blood clot in a vein that runs between the skull and brain.

She was admitted to New York-Presbyterian Hospital the same day for treatment with blood thinners and released last Wednesday.

Clinton is expected to resign from the State Department soon. President Barack Obama has nominated Massachusetts Sen. John Kerry to replace her.