A Model-Based Estimation of RSV-Attributable Incidence of Hospitalizations and Deaths in Italy Between 2015 and 2019

Introduction: Respiratory syncytial virus (RSV) incidence is known to be underestimated in adults due to its infrequent diagnostic testing and lower sensitivity of single nasal/nasopharyngeal swab PCR testing outside of the early childhood period. RSV can trigger acute cardiac events as well as cause respiratory disease. Consequently, we used a model-based study to estimate RSV-attributable hospitalization and mortality incidence among adults in Italy between 2015 and 2019. Methods: Through a database predisposed by CREA Sanit & agrave;, by extracting monthly data from the Italian hospitalization collection data of the Ministry of Health and the Italian National Institute of Statistics (ISTAT) data (mortality), we estimated yearly RSV-attributable incidence of events for different cardiorespiratory outcomes. We used a quasi-Poisson regression model, which accounted for periodic and aperiodic time trends and viral activity proxies. Results: The yearly RSV-attributable cardiorespiratory hospitalization incidence increased with age and was highest among adults aged >= 75 years (1064-1527 cases per 100,000 person-years). Similarly, the RSV-attributable cardiorespiratory mortality rate was highest among persons aged >= 75 years (59-85 deaths per 100,000 person-years). Incidence rates for RSV-attributable hospitalizations and RSV-attributable mortality were on average 2-3 times higher for cardiorespiratory than respiratory disease alone. Incidence rate based on RSV-specific ICD codes only were 405-1729 times lower than modeled estimates accounting for untested events. Conclusion: RSV causes a substantial disease burden among adults in Italy and contributes to both respiratory and cardiovascular conditions. Our results emphasize the need for effective RSV prevention strategies, particularly among older adults.