An outbreak of herpes simplex virus type 1 in an intensive care nursery.

Neonatal herpes simplex infection is not a common occurrence but one which warrants particular concern. An 1800-g premature infant who developed respiratory distress and died at 12 days unexpectedly yielded HSV from a culture of cerebrospinal fluid. There were no mucocutaneous lesions. Ten days later three other infants (ages 40, 69 and 11 days) developed vesicles which yielded herpes simplex. Health care staff cohorts were assigned to "clean" or "exposed" nursery areas. The three secondarily infected cases were treated with vidarabine and did not develop systemic symptoms. Typing of the isolates using immunofluorescence and monoclonal antibodies revealed all to be herpes simplex type 1. Restriction endonuclease cleavage of viral DNA determined that the isolates from the four infants were identical. The mothers of the infants denied any history of recent or recurrent herpes, and their cervical cultures were negative. The source of the outbreak has remained unknown. The possibility of manual transmission to the secondary cases remains likely despite standard infection control practices. Cohort isolation of all exposed patients prevented further spread.