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Abstract
The occurrence of chickenpox in pediatric hospitals disrupts routine care of immunologically normal patients and is potentially life-threatening to immunosuppressed patients.1, 2 Guidelines for prevention of nosocomial chickenpox that are published by the Center for Disease Control recommend that patients with chickenpox be placed in isolation rooms and that personnel entering the room wear gown, gloves, and mask.3 These recommendations are based on observations suggesting that chickenpox is transmitted via the air.4 5 6 7 8 9 However, airborne spread has never been unequivocally demonstrated, and the reports of varicella spread by this route have not adequately excluded alternative modes of transmission.4 5 6 7 8 9 Moreover, the low secondary attack rate after exposure to chickenpox in nonresidential settings suggests that airborne spread is less important than transmission by direct contact.10 We describe an epidemic of chickenpox occurring in a pediatric hospital in which airflow and epidemiologic studies document transmission by an airborne route. Certain rooms on the ward had high attack rates of chickenpox (Fig. 2). Since some children were moved from room to room during hospitalization of the index patient, it was not always possible to identify the room in which chickenpox was actually acquired. In spite of an exhaustive investigation, we were unable to discover any evidence that chickenpox was spread by personnel. Since the index patient was isolated during her entire stay and was critically ill, no contact occurred between her and any patient who subsequently had chickenpox. The index patient had varicella pneumonia and was undergoing mechanical ventilation that produced constant, forced expulsion of exhaled air and droplet nuclei. Since her room was at positive pressure with respect to the hall and the outside of the building, these conditions promoted the escape of virus-contaminated air.