Clinton, 65, who's expected to leave her job after serving as America's top diplomat during President Barack Obama's first term, is recovering at home and is being monitored by doctors, a statement by aide Philippe Reines said.
No further details were immediately available.
The statement said Clinton was dehydrated because of the virus and she fainted and sustained a concussion. She will continue to work from home in the week ahead and looks forward to being back in the office soon, the statement said.
The Senate Foreign Relations Committee said it won't hear from Clinton as planned at a Thursday morning hearing into the Sept. 11 attack against a U.S. diplomatic outpost in Benghazi, Libya, that killed four Americans, including the U.S. ambassador. She also was scheduled to testify that afternoon before the House Foreign Affairs Committee.
Yesterday, Clinton's aides informed the Senate committee chairman, Sen. John Kerry (D-Mass.), about her health, and he "insisted that, given her condition, she could not and should not appear" as planned, said his spokeswoman, Jodi Seth. Senior department officials are to testify instead.