Estimating the burden of RSV- and influenza-associated ED visits, hospitalizations, ICU admissions, and deaths across age and socioeconomic groups in New York State, 2005-2019.

backgroundRespiratory syncytial virus (RSV) and influenza are leading causes of severe respiratory illness. With multiple RSV prophylactics now available for different age groups, we aimed to assess the pre-intervention burden of RSV across severity levels and risk groups and contextualize the estimates by comparison with influenza.

methodsWe obtained monthly time series data on emergency department (ED) visits, hospitalizations, intensive care unit (ICU) admissions, and deaths by age group, ZIP code, and cause for New York state from 2005 to 2019. Socioeconomic status (SES) of the ZIP codes was classified using supervised principal component analysis (PCA). We estimated the incidence of events attributable to RSV and to influenza using hierarchical Bayesian regression models. Additionally, we assessed severity, defined by ICU admission and mortality risks, as well as the recording fraction (i.e., percent of estimated true virus-associated outcomes recorded as being due to the specific virus), stratified by age, SES, and over time.

resultsThe estimated annual incidence of RSV-associated ED visits, hospitalizations, and ICU admissions was highest in infants under 1 in the low SES group (8,100 [95% credible interval (CrI): 7,900-8,200] ED visits, 2,240 [95% CrI: 2,200-2,290] hospitalizations and 330 [95% CrI: 320–350] ICU admissions per 100,000 person-years). The incidence of RSV-associated deaths was highest among adults aged 85 years old and above (61 [95% CrI: 49–74] per 100,000 person-years). In contrast to RSV, the burden of influenza was greatest in age groups 65 years and above. The risk of ICU admission varied by patients’ age and SES, and the mortality risk increased steeply with age for both pathogens from < 2% among infants under 1 to > 10% for the oldest age group (RSV: 11.9% [95% CrI: 9.6–14.3%], influenza: 14.4% [95% CrI: 13.1–15.6%] among age groups 85 year age and above). Incidence varied by epidemic year and season, and we observed an increasing recording fraction of RSV among all age groups over the study period.

conclusionsRSV and influenza contribute significantly to the burden of ED visits, hospitalizations, ICU admissions, and deaths, particularly among infants and older adults. Although the recording fraction of RSV increased over the study period, it remains lower, particularly for adults. Our findings reveal a substantial disparity in RSV ED visits and hospitalization burden by SES, particularly among younger age groups. CLINICAL TRIAL NUMBER: Not applicable.