ALASKA State officials said Friday they are investigating a mystery illness that has sickened about 60 people, mostly tourists traveling to Alaska by bus. . . . A WOMAN found wandering along a highway in a daze near her Lenexa, Kan., home was charged Friday with decapitating her 6-year-old son. Police said they have no motive in the child's slaying. . . . FORMER President Jimmy Carter said Friday in Atlanta he will visit Nicaragua next week to co-chair a conference aimed at resolving property disputes.