Viromes in Infants Presenting With a Septic Syndrome

Fever in infants under three months of age is a high-stakes clinical condition because severe bacterial infections occur in up to 20-25% of cases, while clinical signs alone cannot reliably distinguish bacterial from viral illness. Due to immune immaturity, management is often aggressive, involving hospitalization, lumbar puncture, and intravenous antibiotics. Although molecular diagnostics (multiplex PCR), bacterial biomarkers (CRP, procalcitonin), and clinical algorithms have improved care, approximately one quarter of cases still lack a confirmed etiology-most often because viral infections are difficult to definitively establish. This research project aims to improve etiological diagnosis in febrile young infants by systematically evaluating multiplex molecular tests and novel host-response biomarkers (including interferon-induced proteins) using minimally invasive nasal swabs. By correlating these results with final clinical diagnoses-classified as confirmed or probable viral or bacterial infections-the study seeks to clarify the role of these diagnostic tools in early infancy. Seasonal variations as well as environmental and socio-economic factors will be analyzed. A biological sample collection will be constituted for future analyses.The ultimate goal is to enhance diagnostic precision, reduce unnecessary hospitalizations and antibiotic exposure, and optimize the management of febrile infants.