RSV was common wherever children sought care
RSV was detected in 39.8% of the 2,000 children in the study, or 796 children. The estimate's 95% confidence interval, a range showing the statistical uncertainty around it, ran from 37.7% to 42.0%. Positivity was highest among children admitted through emergency departments, at 50.0%. It was 36.3% among children discharged from emergency departments, 36.5% among primary-care children with lower respiratory tract infection, and 12.7% among those in a primary-care upper respiratory tract infection group.
The researchers ran a prospective surveillance study of children under 3 with respiratory tract infection symptoms who presented to participating primary, secondary or tertiary care sites. The final analysis included 410 primary-care participants and 1,590 from secondary or tertiary care; the 318 children in the upper respiratory tract infection substudy were part of that analysis. The results therefore describe RSV among symptomatic children who reached healthcare, rather than infection in the wider community.
The difference was clearest in hospital outcomes
RSV-positive children also had more primary-care contact before recruitment. Any primary-care contact was recorded for 67.2% of RSV-positive participants, compared with 52.1% of RSV-negative participants. Face-to-face contact was reported for 59.0% versus 43.8%. Among children initially discharged, later readmission was 7.9% versus 6.5%, a difference the study did not find statistically significant.
RSV-positive children were hospitalised more often than RSV-negative children: 73.0% compared with 48.5%. A univariable logistic-regression analysis, a statistical method used to compare the odds of an outcome between groups, gave an odds ratio of 2.86 for hospitalisation, with a 95% confidence interval of 2.36 to 3.47. The median stay was four days for RSV-positive children and three days for RSV-negative children. The odds of admission to a high-dependency unit were also higher, with an odds ratio of 1.92 and a 95% confidence interval of 1.30 to 2.84. The odds of paediatric intensive-care admission had an odds ratio of 2.11, with a 95% confidence interval of 1.28 to 3.46.
The hospital burden was not confined to children with significant underlying comorbidity or prematurity. Among hospitalised RSV-positive participants, 70.1% had no significant underlying comorbidity or prematurity, equivalent to 411 of the 580 children in that group.
The youngest children faced the highest odds
Within the RSV-positive group, any prematurity was associated with higher odds of hospitalisation, with an odds ratio of 2.25. The association was stronger for infants under 3 months, whose odds of hospitalisation had an odds ratio of 6.61. For high-dependency or intensive-care admission, the odds ratios were 3.86 for prematurity, 19.61 for age under 3 months and 4.37 for congenital cardiac disease.
Those estimates came with different levels of precision. For children under 3 months, the 95% confidence interval for high-dependency or intensive-care admission ran from 4.60 to 83.51, a wide range that leaves considerable uncertainty about the size of the association. The hospitalisation estimate for the same age group had a narrower interval of 3.45 to 12.68.
The costs extended beyond hospital wards
Testing found two or more respiratory viruses in 40.8% of RSV-positive participants, compared with 18.3% of RSV-negative participants. Rhinovirus was the most common coinfecting virus, followed by adenovirus.
Average healthcare cost was £1,811 per RSV-positive participant, compared with £1,295 per RSV-negative participant. That is an average difference of £516 per participant. Cost information was unavailable for 15.2% of the full sample, or 304 of 2,000 participants, so the estimate was based on less than the complete dataset.
Caregiver work loss did not clearly differ between groups. Among 601 caregivers who reported it, the average was about 32 hours, or roughly four working days. RSV-positive and RSV-negative groups reported 32.5 and 32.27 lost hours, respectively, with equivalent costs of £515.47 and £512.51. The study did not find a statistically significant difference.
What the study can and cannot show
These results show an association between RSV positivity and heavier healthcare use among symptomatic children in the participating services. They do not show that RSV itself caused the higher hospitalisation or critical-care figures. The outcome comparisons used univariable logistic regression and reported odds ratios with 95% confidence intervals, so the results should be read as comparisons between groups, not as proof of a causal effect.
The study's funding entry lists Sanofi. The supplied disclosures report that MB, RK and NV were Sanofi employees with Sanofi stock or stock options. The document also warns that its supplemental material was not vetted by BMJ and may not have been peer-reviewed.
Paper data and sources
Original title: High respiratory syncytial virus burden in children under 3 years of age across all care levels in England.
Authors: Emma C Carter, Helen Hill, Carla Solórzano et al.
Journal/Repository: BMJ open respiratory research
Status: Corrected publication
First online: 2026-08-20
DOI: 10.1136/bmjresp-2025-003996
Original paper · Full text