Aims and Objectives This study aimed to explore the impact of respiratory viral testing on the prevalence of invasive bacterial infections (IBI) in febrile infants up to ninety days of age. Infants in this age group are at high risk for bacteraemia and meningitis, collectively termed IBI, and tend to present with non-specific symptoms making risk assessment challenging. The study is novel in its focus on SARS-CoV-2, Influenza, and Respiratory Syncytial Virus (RSV) due to their availability as point-of-care tests (POC) and therefore their potential influence on the diagnostic pathway within the emergency care setting.

Method and Design This secondary analysis used data from the Febrile Infant Diagnostic assessment and Outcome (FIDO) study, a prospective observational cohort study conducted across 35 sites in the UK and Ireland under the PERUKI network. Infants aged ≤90 days with a fever ≥38°C were included. The results of commercially available tests for SARS-CoV-2, Influenza, and RSV were compared against the presence of IBI, defined as a pathogen identified in blood or CSF by culture or molecular testing. Analysis was conducted with descriptive statistics (SPSS version 23).

Results and Conclusion Of 1821 infants recruited to FIDO, 1395 underwent respiratory viral testing; 339 (24.3%) tested positive. Infants with a positive viral test had significantly lower IBI rates compared to those with a negative test (1.5% v 3.8%, p=0.034). In infants aged 29-90 days, those with a positive viral test had an IBI rate of 0.7% versus 3.2% for negative tests (p=0.015).

These findings indicate that young febrile infants with a positive respiratory viral test for SARS-CoV-2, RSV or Influenza are at lower risk of IBI. Infants over 28 days of age with a positive test represent the lowest-risk cohort. Respiratory viral POC tests may therefore hold potential to streamline management by reducing painful procedures, decreasing admission rates or length of stay and enhancing antimicrobial stewardship.