Background: Acute viral bronchiolitis caused by respiratory syncytial virus (RSV) may be a manifestation of high severity in neonatal-ICU (NICU) patients, with high risk of in-hospital cross transmission and outbreaks. During the epidemic seasonal period, intense viral circulation occurs in community; thus, transmission in the NICU is difficult to control. Objective: We describe an outbreak that occurred in a NICU in a public hospital in So Paulo state, Brazil. We also discuss the role of admitting external newborns with community-acquired virus in the incidence of these outbreaks in the NICU. Methods: In 2017 in Campinas, an RSV epidemic occurred during the seasonal period, resulting in a outbreak at the Campinas maternity hospital. A retrospective investigation was performed, and patients were analyzed for clinical and epidemiological characteristics and for risk factors for poor prognosis. We included neonates admitted in NICU with positive nasal lavage for RSV from April to July 2017. Statistical analysis were performed with 2 test for the categorical variables and the Student t test for the continuous variables comparing the newborn group from the community (external) with infected newborns in the hospital (internal). P < .05 was considered significant. Results: Of 44 neonates with RSV during this period, 32 were external and 12 were internal (Fig. 1). The mean gestational age of the external neonates was 38 weeks and 2 days, whereas the mean gestational age of the internal neonates was 29 weeks and 1 day (P < .001). The hospitalization time was higher in the internal group (P < .001). Table 1. One death associated with infection occurred in the internal group. Community neonates (external group) were mostly term-born, with no comorbidities, and they had a more favorable clinical course. In the literature, neonates infected with RSV at the hospital have several risk factors for poor prognosis, with a 13.5% mortality rate. Discussion: RSV outbreaks have great relevance in hospital settings, especially in the NICU, where there are a large number of vulnerable patients and a high risk of in-hospital cross transmission. Neonates infected with RSV at the hospital have several risk factors for poor prognosis, including high mortality. Therefore, it is important to discuss the exposure of this population to community-based infectious agents, mainly viral, and the risk of accepting patients from the community to be admitted to the NICU.