case was a patient who was admitted to Prince of Wales Hospital, a 1000-bed general
hospital. 4 The patient had been placed in an open ward with 20 other patients because the
outbreak had not been recognized. The staff did not use any personal protective equipment
during that period. We studied all physicians, nurses, medical students, and allied health
staff who had worked at least one 4-hour shift in that ward during the 8 days between the …