A retrospective study of pediatric respiratory hospitalizations in Italy found that respiratory syncytial virus (RSV) and influenza infection quadrupled the risk of severe disease and ICU admission compared with cases of other viral respiratory infections.1 According to the data, patients with comorbidities, including cardiac or pulmonary disease or congenital malformations, are at a fivefold increased risk of severe outcomes.
“From clinical experience, we know that kids with preexisting conditions who get RSV or influenza are more likely to need to come into the hospital, that it often takes them longer to get better, and that they are likely to be sicker while they’re here,” said Sarah P. Cohen, MD, Assistant Professor of Pulmonary Disease, Critical Care Medicine, and Pediatrics at The Ohio State University Wexner Medical Center and Nationwide Children’s Hospital. “This study confirms what we tend to see—that flu and RSV are associated with the most severe illness. These are the most concerning respiratory viral infections in our populations.”
The multicenter cohort study drew data from an active pediatric surveillance system designed to promote early detection of emerging pediatric infection trends. It comprised 12 pediatric referral centers across Italy and included data from 516 children who were hospitalized with respiratory symptoms between September 2023 and December 2024. The median age was 13.3 months, and 55.8% were male.
Most of the children admitted with respiratory symptoms were aged 60 months or younger (83.7%), and 13.4% had a preexisting comorbidity. Only 1.8% of infants in the study were born earlier than 37 weeks gestation. Just 7.7% of children admitted had received influenza vaccination, and the study was conducted before the widespread introduction of nirsevimab in Italy for RSV prophylaxis in infants.
Nearly all of the children admitted (95.3%) tested positive for at least one respiratory virus. Viral pathogens included rhinovirus/enterovirus (32.2%), adenovirus (26.0%), influenza (20.2%), human coronavirus (14.0%), RSV (13.0%), metapneumovirus (9.3%), parainfluenza (4.8%), and bocavirus (4.7%). Most children (67.4%) had a single infection, while 27.9% had coinfection with at least two pathogens.
Children with influenza virus had the highest rate of ICU admission, at 11.5% vs 2.2% for other pathogens (P < .001), as well as the longest hospital stay, at 8.9 days vs 4.2 days (P = .02). Patients with RSV had the highest rate of supplemental oxygen (67.2%), followed by bocavirus (50.0%) and metapneumovirus (43.8%). Influenza, RSV, and bocavirus were associated with significantly higher clinical severity scores, whereas human coronaviruses, including SARS-CoV-2, had the lowest clinical severity scores.
Most viral coinfections involved two pathogens (25.9%), with adenovirus being the most common coinfection (60.4%). Nonrespiratory viral coinfections were detected in 9.9% of children, and 28.7% had bacterial coinfections. Infants aged 3 months to 12 months and children aged 12 months to 60 months had higher rates of coinfection (31.6% and 35.6%, respectively) than those older than 60 months, at 22.6% (P < .001).
Bacterial coinfections were more common in younger children, but there was no association between age or respiratory coinfection with disease severity. Children with coinfections did not have worse outcomes compared with those with a single viral infection.
More children older than 60 months were admitted to the ICU (8.3% vs 3.2% [P = .04]), and infants younger than 3 months received oxygen more often (45.4% vs 26.7% [P = .05]). There were no differences in age for clinical severity score, length of stay, or mortality.
Children with preexisting comorbidities were more likely to be admitted to the ICU (13.0% vs 2.7%). Patients with congenital malformations were more often admitted to the ICU (21.4%). Those with chronic conditions had a longer length of stay (7.5 days vs 5.2 days [P =.03]) and a higher mean clinical severity score (2.3 vs 1.7 [P = .004]). Preexisting cardiac or pulmonary diseases or congenital malformations were associated with increased risk of severe infection.
“This study confirms that kids with preexisting conditions should absolutely be immunized against influenza, and really all kids older than 6 months of age,” Dr. Cohen said. “All infants who are eligible should be getting RSV prophylaxis. If mom is worried about giving the baby an extra shot, then mom should get vaccinated against RSV at least a couple of weeks before delivery. And if, for whatever reason, mom didn’t get vaccinated before delivery, the baby should be getting prophylaxis during the birth hospitalization. If we could get all those infants proper prophylaxis early in life, that would significantly decrease morbidity.”
References
1. Moracas C, Poeta M, Venturini E, et al. Pathogen and patient characteristics and the severity of viral respiratory infections in children. JAMA Netw Open. 2026;9(2):e260129. doi:10.1001/jamanetworkopen.2026.0129
