Influenza A/H1N1/2009 outbreak in a neonatal intensive care unit

Outbreaks of influenza A/H1N1/2009 in neonatal intensive care units (NICUs) have been reported only rarely. Annual vaccination of all healthcare workers (HCWs) against seasonal influenza is recommended but compliance is low and exposure to infected staff as the source of nosocomial outbreaks has been described.

To report an outbreak of influenza A/H1N1/2009 in a tertiary level NICU that resulted in considerable morbidity.

When the first influenza case was identified, a prospective study was conducted and control measures were implemented to reduce the spread of infection throughout the NICU. Neonates who developed influenza were treated with oseltamivir, and exposed neonates were given prophylaxis with oseltamivir.

Two infected infants who were immature by gestational age and birth weight developed pneumonitis requiring respiratory support, and a third full-term neonate had a mild uncomplicated illness. No significant adverse effects were noted during antiviral treatment or prophylaxis. The investigation identified infected HCWs as the likely source of the outbreak. There was a very low influenza vaccination rate of 15% among nursing staff.

Nosocomial influenza can cause considerable morbidity, especially in high risk neonates, and is readily transmissible in the NICU setting by unvaccinated staff members who contract influenza. To prevent outbreaks, in addition to infection control measures, the implementation of HCW vaccination is very important. Oseltamivir treatment was well-tolerated even among premature infants and appeared to be effective, because neonates with influenza had complete recovery and only one of those who received prophylaxis developed the infection.