Hospitalizations Linked With RSV Likely Underreported in Older Adults

Associated hospitalization burden could be 2.2 times higher in older adults with respiratory syncytial virus (RSV) than was previously estimated, according to a recent study.

Older adults hospitalized with respiratory syncytial virus (RSV) have a higher associated hospitalization burden than has previously been reported, according to a review published in Infectious Diseases and Therapy.

Hospitalizations could be up to 2.2 times higher than previously thought.

RSV is an acute respiratory infection (ARI) that affects older adults aged more than 65 years. Disease burden has been reported in past reports but were based on studies that had various ways of testing for RSV, which could underestimate the true burden of RSV. This review aimed to “improve the understanding of RSV-associated ARI hospitalization burden in older adults in high-income countries by adjusting for case under-ascertainment…”

The researchers used MEDLINE, Embase, Global Health, CINAHL, Web of Science, and Global Index Medicus to search for relevant studies on the topic, with all studies published between January 1, 1996, and December 16, 2021. Studies were included if they reported on adults aged 60 years or above who were infected with RSV and needed hospital admission, reported on RSV in the older adult population, had available data for 12 consecutive months, and reported hospital admission rates.

Studies were excluded if RSV infection was not the primary outcome, the case definition was not clearly defined or was narrower than ARI, focused on specific populations, were estimates based on modelling approaches, or were not in the English language.

Data for location and country, study period, clinical specimen, reported estimates by age group, RSV testing method, and study period were all collected. Quality assessment was done using the Joanna Briggs Institute critical appraisal tools.

Adjustment for clinical specimen and testing approaches were both considered. For the former, the researchers calculated the proportion of detection in every possible combination compared with the gold standard. Rapid antigen testing was also used to calculate the proportion of detection. The products of the 2 detection proportions obtained were calculated.

The pooled RSV-associated ARI hospitalization rate was the primary outcome and the secondary outcome was the pooled proportion of RSV in all-cause ARI hospitalizations. RSV detection was inflated for each study to generate adjusted pooled proportion of RSV. A generalized linear mixed-effects model was used to generate a pool RSV-associated ARI hospitalizations. Case fatality ratio was applied to the number of RSV-ARI hospitalizations to gather the number of in-hospital deaths for patients with RSV-ARI.

A total of 12 studies were used in this review, with 8 coming from the United States, 2 from Finland, and 2 from New Zealand; half of the studies were assessed as high quality.

There were 6 studies that reported RSV-associated ARI hospitalization rate estimates. In patients aged 65 years and older, the hospitalization rate was 157 per 100,000 (95% CI, 98-252), which corresponded to 356,000 (95% CI, 222,000-572,000) hospitalizations for RSV-associated ARI. The adjusted annual hospitalization rate for individuals aged 65 years and older was 347 per 100,000 (95% CI, 203-595), which is about 787,000 (95% CI, 460,000-1,347,000) RSV-associated ARI hospitalizations, 2.2 times the unadjusted estimate. Heterogeneity was high, with the adjusted estimates having reduced heterogeneity compared with unadjusted estimates (95% vs 94% for 65 years and older; 58% to 47% for 85 years and older).

There were 8 studies that reported the proportion of RSV detection in ARI hospitalization. RSV was found in 7.9% (95% CI, 5.4-11.5) of adults aged 65 years or older that were hospitalized for ARI when not adjusted for under ascertainment. When adjusting for under-ascertainment, the proportion increased to 16.5% (95% CI, 10.3-25.2). The number of RSV-associated ARI hospitalizations were approximately 267,000 (95% CI, 182,000-386,000) without adjustment and 554,000 (95% CI, 347,000-849,000).

The mortality rate was also assessed. The pooled case fatality ratio for adults aged 65 years and older was 6.1% (95% CI, 3.3%-11.0%) and was 5.3% (95% CI, 3.9%-7.3%) for adults aged 60 years and older.

The researchers concluded that the “true RSV-associated hospitalization burden was likely substantially underestimated” with an estimated 2.2 times higher hospitalization rate than had been reported in previous studies.


Li Y, Kulkarni D, Begier E, et al. Adjusting for case under-ascertainment in estimating RSV hospitalization burden of older adults in high-income countries: a systematic review and modelling study. Infect Dis Ther. Published online March 20, 2023. doi:10.1007/s40121-023-00792-3

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