An outbreak of influenza A in a neonatal intensive care unit

OBJECTIVES: Investigation of an outbreak of influenza A in a neonatal inten sive care unit (NICU) with examination of risk factors for infection and ou tcomes. DESIGN: Retrospective cohort study of infants admitted to the unit during t he outbreak period. Prospective survey of NICU staff and mothers of infants in the cohort study. SETTING: Level III nursery in a university-affiliated tertiary referral cen ter. RESULTS: Nineteen infants in the NICU were infected with influenza A. There were six symptomatic cases and one death who had evidence of virus-associa ted hemophagocytic syndrome at autopsy. Amantadine prophylaxis was offered to the NICU staff, and amantadine therapy was given to five of the six symp tomatic infants. Mechanical ventilation, gestational age, birth weight, Cli nical Risk Index for Babies score, and twin pregnancy were associated with acquisition of influenza A on univariate analysis. Mechanical ventilation ( odds ratio [OR], 6.2; P=.02) and twin pregnancy (OR, 7.0; P=.04) remained a s significant risk factors for infection on multiple logistic regression an alysis. Only 15% of respondents to the NICU staff survey were vaccinated ag ainst influenza. There was no association between a history of an influenza -like illness during pregnancy and acquisition of influenza A by infants of mothers who responded to the maternal survey (OR, 0.91; P=1.0). CONCLUSIONS: Influenza A is an important pathogen in the neonatal populatio n and is readily transmissible in the NICU setting.