Estimated Incidence of Hospitalisations and Deaths Attributable to Respiratory Syncytial Virus Infections in Adults in Australia Between 2010 and 2019.

Background: Respiratory syncytial virus (RSV) morbidity and mortality in adults are often underestimated due to nonspecific symptoms, limited standard-of-care testing and lower diagnostic testing sensitivity compared with children. To accurately evaluate the RSV disease burden among adults in Australia, we conducted a model-based study to estimate RSV-attributable cardiorespiratory hospitalisation incidence and mortality rate.

Methods: A quasi-Poisson regression model was used to estimate RSV-attributable cardiorespiratory, respiratory and cardiovascular events, using weekly hospitalisation and mortality data from 2010 to 2019, accounting for periodic and aperiodic time trends and viral activity and allowing for potential overdispersion. The time-series model compared the variability in confirmed RSV events alongside variability in all-cause cardiorespiratory events identified from ICD-10-AM codes to estimate the number of RSV-attributable events, including undiagnosed RSV-related events.

Results: RSV-attributable incidence of cardiorespiratory hospitalisations increased with age and was highest among adults ≥ 65 years (329.5-386.6 cases per 100,000 person-years), nine times higher than in adults 18-64 years. The estimated incidence of RSV-attributable respiratory hospitalisations in adults ≥65 years (219.7-247.8 cases per 100,000 person-years) was 35-fold higher than in adults 18-64 years. RSV-attributable deaths accounted for 4% to 6% of cardiorespiratory deaths in adults ≥ 65 years, with RSV-attributable mortality rates ranging from 65.6 to 77.6 deaths per 100,000 person-years and respiratory mortality rates ranging from 20.3 to 24.0 deaths per 100,000 person-years, both 70-fold higher than in adults 18-64 years.

Conclusions: This study identified substantial RSV-associated morbidity and mortality among Australian adults and is the first study to report RSV-attributable mortality rates for Australia that account for untested events.