Cytomegalovirus (CMV) is a betaherpesvirus, the impacts of which are well known to clinicians providing post-transplant cystic fibrosis care. Lung transplant recipients have the highest risk of any solid-organ transplant for CMV reactivation and ganciclovir resistance [1, 2]. Furthermore, CMV reactivation increases the risk of chronic lung allograft dysfunction. However, even in general populations, CMV seropositivity is associated with adverse outcomes including cognitive impairment, frailty, heart disease and all-cause mortality [3-5]. How CMV may contribute to disease is not evident but many streams of evidence suggest CMV replication in inflamed sites contributes to exaggerated inflammation and tissue injury [6]. Individuals with cystic fibrosis experience chronic inflammation within the airways leading to remodelling and eventually respiratory failure. Indeed, inflammatory biomarkers in the sputum and serum of cystic fibrosis patients correlate with short-and long-term outcomes [7]. We hypothesised that CMV may represent an unrecognised contributor to cystic fibrosis lung disease. We performed a detailed chart review of all Calgary Adult Cystic Fibrosis Clinic patients who were referred for lung transplantation, where CMV IgG testing would be performed. CMV serostatus, demographics, infecting pathogens, markers of nutrition and lung function from last clinical encounter were recorded for those who were transplanted or succumbed to disease. Our primary outcome was a composite end-point of age at lung transplantation/death without transplant. We also analysed the outcomes of death and lung transplant separately by CMV serostatus, and conducted a stratified analysis per time period to account for improvements in care