Risk of Bacterial Infections in Febrile Infants 61 to 90 Days Old With Respiratory Viruses

The objective of this study was to describe the prevalence of urinary tract infections (UTIs), bacteremia, and bacterial meningitis among febrile infants aged 61 to 90 days with and without respiratory viral infections. We used data from the Pediatric Emergency Care Applied Research Network (PECARN) Registry, comprised of pediatric visits from 17 emergency departments. Our cohort included infants aged 61 to 90 days with temperatures of at least 38°C, urinalyses/urine dipsticks and/or blood cultures, and respiratory viral testing performed between January 1, 2012, and April 30, 2024. We calculated the prevalence, with 95% CIs, of UTIs, bacteremia, and bacterial meningitis, stratified by presence and types of respiratory viral infections. We included 3678 visits; 1725 (46.9%) infants tested positive for respiratory viruses. Compared with viral-negative infants, respiratory viral-positive infants had a lower prevalence of UTIs (4.4% [95% CI 3.5-5.6%] vs 12.5% [95% CI 11.0-14.2%]) and bacteremia (1.0% [95% CI 0.5-1.8%] vs 3.0% [95% CI 2.1-4.1%]). No respiratory-viral positive infants had bacterial meningitis, whereas 4 viral-negative infants had meningitis. The prevalence of UTIs ranged from 2.2% to 5.2% in infants who tested positive for influenza, respiratory syncytial virus, or SARS-CoV-2, all lower than viral-negative infants. SARS-CoV-2 positive infants had a lower prevalence of bacteremia compared with SARS-CoV-2 negative infants (0.9% [95% CI 0.3-1.9%] vs 3.1% [95% CI 2.0-4.6%]). The prevalence of bacterial infections is lower in respiratory virus-positive febrile infants aged 61 to 90 days. These findings may help inform use of respiratory viral testing in the evaluation for UTIs, bacteremia, and meningitis in this age group.