HOUSTON — Former president George H.W. Bush has been admitted to the intensive care unit at a Houston hospital ‘‘following a series of setbacks including a persistent fever,’’ but he is alert and talking to medical staff, his spokesman said Wednesday.

Jim McGrath, Bush’s spokesman in Houston, said in an e-mail that Bush was admitted to the ICU at Methodist Hospital on Sunday. He said that doctors were cautiously optimistic about his treatment and that the former president ‘‘remains in guarded condition.’’