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 Sanità, 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.