Fever in an infant is one of the leading reasons prompting emergency department visits throughout the U.S. Often these patients have viral infections; however, serious bacterial infections are always a concern. While there is current guidance for febrile infants less than 60 days old, there is limited data for older infants. A recent article in Pediatrics looked at the prevalence of co-infection in this slightly older patient population.
Using data from the Pediatric Emergency Care Applied Research Network Registry, this study compared prevalence of serious bacterial infections in febrile infants 61-90 days old with and without respiratory viral infections. The study period ran from January 2012 through April 2024. An infant was classified as being febrile if they had a documented temperature of at least 38.0 degrees Celsius. Bacterial infections evaluated were urinary tract infections, bacteremia and bacterial meningitis. These infections were analyzed in relation to presence of RVI, as well as by specific virus present.
This study included 3,341 ED visits where workup for UTI was completed, and 2,264 where workup for bacteremia and/or meningitis was done. When compared to infants without RVI, those positive for RVI had a lower prevalence of UTIs (4.4% vs. 12.5%). Additionally, RVI-positive infants had lower prevalence of bacteremia without meningitis (1.0% vs. 3.0%); no infants positive for RVI had bacterial meningitis, and four RVI-negative infants had bacterial meningitis. Interestingly, the prevalence of UTIs in RVI-positive infants seemed highest in those positive for rhinovirus (6.2%), while the prevalence of bacteremia without meningitis was lower in those positive for influenza, RSV and SARS-CoV-2 (0.6%-0.9%) compared to those positive for rhinovirus (1.4%).
Overall, this study showed that febrile infants 61-90 days old had lower prevalence of serious bacterial infection when testing positive for a respiratory virus, though prevalence was not zero and varied by virus type. These data could help inform the role of viral respiratory testing in this patient population, as well as allow clinicians to risk-stratify the need for additional diagnostic workup for bacterial co-infections.
(Aronson et al. Pediatrics. 2025;156(1): e2025070617. Published online: June 13, 2025.)