A 35-month prospective study on onset of scabies in a psychiatric hospital: discussion on patient transfer and incubation period.

This study was conducted to evaluate the risk factors of scabies introduction into a hospital. We addressed the following question: Do patients transferred from other institutions pose a higher risk than patients from the community? From July 2003 to May 2006, a trained physician surveyed the inpatients and staff of a psychiatric hospital (six wards, 300 beds) on a monthly basis. During the study period, specific infection control measures beyond standard precautions, such as prophylactic treatment, were not adopted. There were 333 newly-admitted patients during the study period and among them, 122 were transferred from other institutions. Seven patients were diagnosed with scabies. Two of these patients were infected while in the hospital (secondary infection), thus the number of introduced scabies cases (index cases) was five. Four of the index cases were transferred from other institutions (three from psychiatric hospitals and one from a nursing home). The source of infection for one index case was unexplained. The rate of scabies infection among transferred patients was 3.3% while the infection rate among patients from the community was 0.5%. Therefore, transferred patients pose a higher risk than those from the community. The average time from admission to diagnosis of scabies was 141 days (range 34-313 days). The hospital personnel checked the skin condition of all patients at admission and none of the four patients showed symptoms of scabies.