Mombasa Governor Hassan Joho has been admitted with malaria, his Communications director Richard Chacha told the Nation on Friday.
Mr Chacha said the governor was taken to The Mombasa Hospital on Monday after complaining of a severe headache.
He further told the Nation that doctors recommended that Mr Joho remain in hospital for further checks.
Mr Chacha said the county boss, who is the deputy leader of the Orange Democratic Movement (ODM), would be discharged on Friday.
Reports of the governor's admission surfaced on Friday morning after former Nigerian President Olusegun Obasanjo visited him.
The governor was last seen in public in Malindi on October 26, when he accompanied ODM leader Raila Odinga to the burial of Michael Ngumbao who was shot and killed on October 15, two days to the Ganda Ward by-election.
Mr Ngumbao was the uncle of newly elected Ganda Ward Representative Reuben Katana.