The proposed study is a unique international collaboration between three large CF research centers. This proposal will determine the impact of early respiratory viral infections on bacterial flora and inflammatory profiles in the CF airway as well as the impact of these pathogens on clinical, physiologic and structural markers of disease.The proposed study is designed to follow infants diagnosed with CF through newborn screening to determine the effect of viral infections on the lower airway microbiome, clinical symptoms, pulmonary function and structural changes during the first year of life. The proposed study will measure lower airway inflammation and infection using BAL, oral swabs, and nasal swabs; outcomes will be assessed through infant lung function testing, computerized tomography scans of the chest, and pulmonary exacerbation rate.