Introduction: Febrile infants with a confirmed viral infection are at lower risk of an invasive bacterial infection (IBI). Several authors recommend individualizing screening in febrile infants aged 1 to 3 months, but there are currently no specific recommendations for neonates. The objective of our study was to determine the prevalence of IBI in febrile neonates with influenzavirus infection.

Methods: Observational descriptive study in febrile infants aged less than 29 days managed in the emergency department with a microbiological diagnosis of influenza over a 21-year period (2004-2023). We excluded patients with an abnormal pediatric assessment triangle or who had received antibiotherapy in the past week.

Results: The sample included 112 patients. Urine culture was performed in all, blood culture in 108 (96.4%) and lumbar puncture in 61 (54.5%). A total of 102 (91.1%) were admitted to hospital, of who 61 (59.8%) received antibiotics. An IBI was identified in one patient (prevalence 0.9%; 95% CI, 0.2%-4.9%): a female aged 8 days with a bloodstream infection by Escherichia coli. Additionally, 7 (6.3%, 95% CI: 3.1%-12.3%) patients presented with a urinary tract infection.

Conclusions: The prevalence of IBI in febrile neonates with influenza infection is very low, with no detection of cases of bacterial meningitis. Confirmation of these results in a multicenter study, which could also identify associated risk factors, would allow a less aggressive approach of low-risk patients.