Using a different surveillance system (the capture–recapture methods), researchers suggested that overall adult hospital rates from RSV are significantly higher than previously reported.

The Vanderbilt University Medical Center–led study reported that with capture–recapture, the estimated overall adult hospitalization rates in Middle Tennessee varied from 8.3 (95% CI, 5.9-15.4) RSV-related hospitalizations per 10,000 persons during the 2016–2017 season to 28.4 (95% CI, 18.2-59.0) hospitalizations per 10,000 persons in the 2019–2020 season.

The proportion of hospitalizations that the Hospitalized Adult Influenza Vaccine Effectiveness Network (HAIVEN) determined ranged from 8.7% to 36.7% of the total capture–recapture estimated hospitalization, whereas the Emerging Infections Program (EIP) detected 23.5% to 52.7% of the total capture–recapture estimated hospitalizations, according to the report in the journal Influenza and Other Respiratory Viruses.

That data are especially important, according to the authors, now that vaccines are available to help ameliorate the disease burden.

The researchers used capture–recapture methods to estimate the number of RSV-related hospitalizations in adults in Middle Tennessee, amalgamating data from the two independent hospitalization surveillance systems during consecutive respiratory seasons from 2016–2017 to 2019–2020. Annual RSV hospitalization rates were calculated using the capture–recapture estimates weighted by hospitals’ market share divided by the corresponding census population.

“Capture–recapture estimates showed that individual traditional surveillance systems underestimated the hospitalization burden in adults,” the study added.

The authors noted, “Determining the burden of RSV infections is of great public health interest to inform and target preventive activities such as vaccination programs. With the recent approval of a RSV vaccine for older adults, it is of vital importance to use surveillance programs to determine RSV burden and monitor the impact of vaccination programs.”

The study team pointed out that RSV-associated symptoms are similar to those caused by other respiratory viruses, so laboratory confirmation is required. In elderly patients, RSV might have atypical symptoms such as confusion, anorexia and falls, they added. Further complicating diagnosis is that RSV can cause “related complications, such as worsening of congestive heart failure or an exacerbation of chronic obstructive lung disease; therefore, making diagnosis based on clinical findings may be challenging in adults,” the authors wrote.

The article explained how RSV has always been a challenging pathogen to detect and is difficult to culture. “While previous RSV rapid antigen tests showed relatively good performance in children, they often performed less effectively in adults due to the requirement for substantial viral quantities to produce a positive test result. This is because older adults typically exhibit lower viral loads in their respiratory secretions.”

Hospitalization rates were highest in adults aged years 65 and older. “The capture–recapture approach can be useful to inform resource allocation and monitor the impact of RSV vaccination policies for older adults,” the authors concluded.

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