Infants Have Higher Risk of Developing Asthma When Hospitalized With RSV

Infants hospitalized with respiratory syncytial virus (RSV) bronchiolitis who were born to parents with asthma had a significantly higher risk of developing asthma in the future, according to investigators of data published in Science Immunology. In their study, the authors wrote that their findings may underestimate the true RSV-attributable asthma risk in human infants.¹

The Asthma and Allergy Foundation of America notes that asthma can occur at any age, even in infancy; however, because asthma often looks different in children than in adults, it can be more difficult to diagnose in younger age groups. In babies or toddlers, asthma symptoms can include fast breathing, working harder to breathe (eg, nostrils flaring or exaggerated belly movement), panting with normal activities (eg, playing), wheezing, persistent coughing, or difficulty eating. To help young patients receive an asthma diagnosis, parents or caregivers should share the family history of asthma and/or allergies, the child’s behavior, breathing symptom patterns, and potential food- or allergy-related triggers.²

Allergic asthma arises from complex genetic and environmental interactions. A prior analysis of a population-wide registry revealed that infants who were hospitalized for human (hRSV) bronchiolitis who are born to parents with asthma have a markedly increased risk of developing asthma. To model this interaction, the investigators conducted another analysis of neonatal mice infected with pneumonia virus of mice (PVM), an RSV analog, before house dust mite (HDM) exposure developed amplified type 2 inflammation and asthma-like pathology.¹

Their findings demonstrated that neonatal mice born to mothers with HDM allergy developed more severe type 2 inflammation and asthma-like symptoms, which was supported by maternal transfer of allergen-specific immunoglobulin G that enhanced HDM uptake and T helper 2 cell (T2H) priming in neonates through virus-induced up-regulation of Fc receptors on neonatal dendritic cells. Additionally, enhanced risk was mitigated when newborn mice were given RSV immunoprophylaxis.¹

"This mechanism of [antibody]-mediated enhanced allergen uptake mediated by viral infection helps explain how two of the best-known asthma risk factors intersect and lead to increased type 2 immunity and asthma in high-risk newborns," the researchers wrote.^1,3 "This in turn promoted [dendritic cell] allergen uptake and caused TH2 cell priming, leading to asthmatic symptoms. Treating pregnant or lactating mothers with anti-RSV antibodies blocked the development of type 2 immunity in newborn mice, suggesting that RSV infection could be a preventable risk factor for asthma."^1,3

The investigators acknowledged limitations of the study, such as recording only asthma and hRSV infections diagnosed at the hospital. This methodology meant that milder disease forms seen only by general practitioners or other health care professionals in community medical care settings were likely missed.

Until recently, it was thought that only severe bronchiolitis requiring hospitalization was a risk factor for asthma, according to the investigators. But recent work using surveillance hRSV detection in cohorts of newborns now suggests that milder hRSV infection could also be a risk factor. Therefore, the authors said their study likely underestimates the true hRSV-attributable asthma risk. Regardless, the data provide insight into maternal factors influencing RSV-associated allergic asthma.¹

"It was initially thought that only severe bronchiolitis requiring hospitalization was a risk factor for asthma, but recent elegant work employing surveillance hRSV detection in cohorts of newborns suggests that milder hRSV infection could also be a risk factor for asthma," the investigators wrote. "Therefore, our study likely underestimates the true hRSV-attributable asthma risk."^1,3

REFERENCES

1. De Leeuw E, Justesen JF, Bosteels C, et al. Maternal allergy and neonatal RSV infection synergize via FcR-mediated allergen uptake to promote the development of asthma in early life. Sci. Immunol. 2025;10(113):eadz4626. doi:10.1126/sciimmunol.adz4626

2. Asthma and Allergy Foundation of America. Asthma in infants. Accessed December 1, 2025. https://aafa.org/asthma/living-with-asthma/asthma-in-infants/

3. MedPage Today. Severe RSV May Increase Inherited Asthma Risk. News release. December 1, 2025. Accessed December 1, 2025. https://www.medpagetoday.com/allergyimmunology/asthma/118758