Clues are sought in mystery illness 08/20/2002 By CHRIS FRATES / The Dallas Morning News IRVING - The death of a 13-year-old girl and the hospitalization of her 15-year-old brother led state, county and city health officials to inspect the family's quarantined home Monday. The girl, Rachel Johnson, died Sunday after experiencing a high fever and breathing problems. Her 15-year-old brother also had trouble breathing four days earlier and was admitted to the intensive-care unit of Children's Medical Center, officials said. The boy remained in isolation Monday. Investigators said they didn't know what caused Rachel's death and the boy's...