Respiratory Syncytial Virus Outbreak in a Brazilian Neonatal Care Unit

Background: Respiratory Syncytial Virus (RSV) is the most important cause of respiratory infection in young children worldwide. The consequences of RSV infection can be dire for children with underlying conditions such as prematurity, cardiac and pulmonary disease, or immunosuppression. Patients, visitors or health care workers with community-acquired RSV infection, may be the cause of nosocomial transmission. RSV outbreaks in neonatal intensive care units (NICU) settings are underreported or underrecognized.

Objective: to evaluate the outbreak of RSV infection in university NICU and control measures impact.

Methods: Neonatal Care Unit is a level III facility in a university hospital. A retrospective review was conducted after the RSV outbreak. A case was defined as a respiratory symptomatic infant and a nasopharyngeal aspirate positive antigen for RSV detected by enzyme immunoassay (Directigen®; Becton Dickinson). The control measures included viral screening by RSV antigen tests of all infants who developed acute respiratory symptoms; cohort and contact precautions for infants RSV infected; meeting with all the staff emphasizing measures to avoid cross infection, including hand washing before and after direct infant care, contact and standard precautions and environmental hygiene; administration of Palivizumab to infants who had contact with the RSV infected case according to the recommendations of the State Health Department. Furthermore, five infants with RSV infection received Palivizumab after symptoms emerged. The visiting policy was changed to allow only parents who were screened negative for respiratory symptoms. During the outbreak the Neonatal Care Unit was closed for new admissions on May 25^th, 2009, measure that was extended to the obstetric ward.

Results: Thirteen infants with birth weight between 555g to 3940g (4 cases <1000g, 6 cases 1001 - 1500g, 3 cases >2500g) had an RSV infection from May 15^th to 28^th, 2009. The severity of the symptoms ranged from lethargy, cough and nasal congestion to increased oxygen requirement, apnea and respiratory failure. Three infants required intubation and mechanical ventilation. One baby with a congenital cardiac disease and other malformations, died. Among the 24 infants who were exposed and used Palivizumab, 66% did not develop a RSV infection, while the others 34% had an RSV infection with mild and favorable respiratory symptoms. The median time for a negative antigen result among infants with RSV infection was 9 days. On June10^th, 2009 it was possible to reopen the Neonatal Care Unit when all infants had negative RSV antigen tests.

Conclusions: The control measures were effective to solve the RSV outbreak. Palivizumab has likely contributed to reduce the gravity of RSV disease and viral elimination time.