Two nosocomial norovirus outbreaks at the neonatal intensive and intermediate care unit

Objective: Norovirus infection in preterm and term neonates rarely has been described. We report on two nosocomial norovirus outbreaks at the neonatal intensive care unit (NICU) and the Neonatal Intermediate Care Unit of the Paediatric Department of the Medical University Graz, Austria. Methods: Observational study on two nosocomial outbreaks of norovirus disease. Symptoms of infection in preterm and term neonates are described. Norovirus was detected in faecal specimen by ELISA and/or PCR technique. Results: Episode I at the NICU: Between January and March 2007, 22 of 44 preterm infants were tested positive for norovirus. Out of 174 faecal specimen 63 (36%) tested positive by ELISA, thirteen specimen tested additionally by PCR were negative. Only the index patient developed symptoms with bloody stools for one day. Viral shedding longer than two weeks was observed in six (27%) patients with maximum 39 days. Episode II at the Neonatal Intermediate Care Unit: Between December 2007 and January 2008 five of 36 neonates were tested positive for norovirus. All had clinical symptoms including vomiting and mild diarrhea in one patient and short-lasting diarrhea in four patients. Isolation of the infants and strict hygiene measures hardly stopped spread of disease. By discharge four of five patients still showed viral shedding. Conclusion: Although spread of disease is difficult to confine, symptoms of disease are generally mild and self-limited in this population. However, we question the reliability of the norovirus-specific antigen assay by the fact of negative PCR testing during the first episode