There are critical knowledge gaps in defining the condition, predicting its severity, and understanding the reasons for hospitalization, including the immature host respiratory immune response to viral infection, heterogeneity in response to different viruses, current interventions, significant practice variation in diagnosis and management and subsequent impact on lung health. To meet the need for deep phenotyping, identify appropriate subgroups, refine the diagnosis and management of these vulnerable patients during their hospitalization, and identify prognostic biomarkers for future airway and parenchymal disease, we propose the VINYL (Viral INfections in the Young Lung) clinical consortium, a pragmatic observational study, to perform deep phenotypic characterization of 1500 babies, infants and toddlers admitted to the pediatric floor and pediatric intensive care unit with viral LRTI. A longitudinal follow-up of participants after discharge using electronic health records and questionnaires and assessment of respiratory status at age 4-5 years will elucidate pulmonary outcomes from early viral LRTI, specifically asthma. Neurocognitive and general development, and sleep will also be assessed during follow up.