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Background: Shared and divergent predictors of clinical severity across respiratory viruses may support clinical and community responses in the context of a novel respiratory pathogen., Methods: We conducted a retrospective cohort study to identify predictors of 30-day all-cause mortality following hospitalization with influenza (N = 45,749; 2010-09 to 2019-05), respiratory syncytial virus (RSV; N = 24 345; 2010-09 to 2019-04), or severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2; N = 8988; 2020-03 to 2020-12; pre-vaccine) using population-based health administrative data from Ontario, Canada. Multivariable modified Poisson regression was used to assess associations between potential predictors and mortality. We compared the direction, magnitude, and confidence intervals of risk ratios to identify shared and divergent predictors of mortality., Results: A total of 3186 (7.0%), 697 (2.9%), and 1880 (20.9%) patients died within 30 days of hospital admission with influenza, RSV, and SARS-CoV-2, respectively. Shared predictors of increased mortality included older age, male sex, residence in a long-term care home, and chronic kidney disease. Positive associations between age and mortality were largest for patients with SARS-CoV-2. Few comorbidities were associated with mortality among patients with SARS-CoV-2 as compared with those with influenza or RSV., Conclusions: Our findings may help identify patients at greatest risk of illness secondary to a respiratory virus, anticipate hospital resource needs, and prioritize local prevention and therapeutic strategies to communities with higher prevalence of risk factors., (© 2022 The Authors. Influenza and Other Respiratory Viruses published by John Wiley & Sons Ltd.)

Objective: Routinely collected health administrative data can be used to efficiently assess disease burden in large populations, but it is important to evaluate the validity of these data. The objective of this study was to develop and validate International Classification of Disease 10th revision (ICD -10) algorithms that identify laboratory-confirmed influenza or laboratory-confirmed respiratory syncytial virus (RSV) hospitalizations using population-based health administrative data from Ontario, Canada., Study Design and Setting: Influenza and RSV laboratory data from the 2014-15, 2015-16, 2016-17 and 2017-18 respiratory virus seasons were obtained from the Ontario Laboratories Information System (OLIS) and were linked to hospital discharge abstract data to generate influenza and RSV reference cohorts. These reference cohorts were used to assess the sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of the ICD-10 algorithms. To minimize misclassification in future studies, we prioritized specificity and PPV in selecting top-performing algorithms., Results: 83,638 and 61,117 hospitalized patients were included in the influenza and RSV reference cohorts, respectively. The best influenza algorithm had a sensitivity of 73% (95% CI 72% to 74%), specificity of 99% (95% CI 99% to 99%), PPV of 94% (95% CI 94% to 95%), and NPV of 94% (95% CI 94% to 95%). The best RSV algorithm had a sensitivity of 69% (95% CI 68% to 70%), specificity of 99% (95% CI 99% to 99%), PPV of 91% (95% CI 90% to 91%) and NPV of 97% (95% CI 97% to 97%)., Conclusion: We identified two highly specific algorithms that best ascertain patients hospitalized with influenza or RSV. These algorithms may be applied to hospitalized patients if data on laboratory tests are not available, and will thereby improve the power of future epidemiologic studies of influenza, RSV, and potentially other severe acute respiratory infections., Competing Interests: The authors have declared that no competing interests exist.

Background: Diagnostic testing for respiratory syncytial virus (RSV) is not routinely performed in adults. We estimated medically attended RSV seasonal incidence in a community cohort of adults ≥50 years old during four influenza seasons (2006-07 through 2009-10)., Methods: Patients seeking care for acute respiratory illness (ARI) were prospectively enrolled and tested for RSV by multiplex RT-PCR. Results from enrolled patients were used to estimate projected cases among non-enrolled patients with ARI. The seasonal incidence of medically attended RSV was the sum of actual and projected cases divided by the community cohort denominator. Since each enrollment period did not include the entire RSV season, incidence estimates were adjusted to account for the statewide proportion of RSV occurring outside the study enrollment period., Results: There were 16,088 to 17,694 adults in the cohort each season and 164 RSV cases in all 4 seasons. The overall seasonal incidence of medically attended RSV was 154 episodes (95% CI, 132-180) per 10,000 persons; the incidence was highest in 2007-08 (179) and lowest in 2006-07 (110). Among persons 50-59, 60-69, and ≥70 years old, RSV incidence was 124 (95% CI, 99-156), 147 (95% CI, 110-196), and 199 (95% CI, 153-258), respectively., Conclusions: The incidence of medically attended RSV increased with age and was similar during four seasons.

Background: Few studies have examined respiratory syncytial virus (RSV) infections in adults. We assessed the characteristics and outcomes of RSV relative to other viral infections., Methods: Patients ≥ 50 years old with acute respiratory illness were recruited for studies of influenza vaccine effectiveness from 2004 through 2010. Nasopharyngeal swabs from enrollees were analyzed for the presence of RSV and other respiratory viruses by multiplex reverse transcription polymerase chain reaction. Clinical data were obtained from interview and medical records., Results: A total of 2225 samples were tested across all seasons. The mean age was 64.2 (SD, 10.7) years; the mean interval from illness onset to sample collection was 4 (SD, 2.2) days. One or more viruses were detected in 1202 (54%) participants. In a multivariable logistic regression model, RSV was associated with ages 65-79 years (vs 50-64 years), symptoms of cough, nasal congestion and wheezing, and longer interval from illness onset to clinical encounter. RSV was not associated with the presence of chronic obstructive pulmonary disease or congestive heart failure in univariate analyses. Hospital admission within 30 days after illness onset was less common among patients with RSV compared to those with influenza (unadjusted odds ratio = 0.54 [95% confidence interval, .29-1.01], P = .06)., Conclusions: RSV is a common cause of acute respiratory illness in adults aged ≥ 50 years; the risk of infection increases with age. Delays in healthcare seeking and reduced risk of hospital admission in patients with RSV suggest a milder course of illness relative to influenza.