1.   It is the cause of the disease that puzzles doctors.

2.   In World War II, many doctors were puzzled by jaundice, a liver disorder afflicting many Allied troops.

3.   Doctors are puzzled by infants in whom the AIDS virus has mysteriously disappeared.

4.   In Australia, meanwhile, doctors were puzzled by an especially odd cluster.

5.   The outbreak has doctors puzzled, and opposing ethnic groups in Macedonia are calling each other hoaxers and poisoners of children.