JMIR Publications

ABSTRACT

Background:

A comprehensive description of the combined effect of SARS-CoV-2 and respiratory viruses (RV) other than SARS-CoV-2 (ORV) on acute respiratory infections (ARI) hospitalizations is lacking.

Objective:

To compare viral etiology of ARI hospitalizations before (8 pre-pandemic influenza seasons, 2012-13 to 2019-20) and during three pandemic years (periods of increased SARS-CoV-2 and ORV circulation in 2020-21, 2021-22, and 2022-23) from an active hospital-based surveillance network in Quebec, Canada.

Methods:

We compared detection of ORV and SARS-CoV-2 during three pandemic years to 8 pre-pandemic influenza seasons in patients hospitalized with ARI who were tested systematically by the same multiplex PCR assay during periods of intense RV circulation. Proportions between pre-pandemic and pandemic years were compared by using appropriate statistical tests.

Results:

During pre-pandemic influenza seasons, overall RV detection was 93% (n=1,384) (48% respiratory syncytial virus (RSV), 31% coinfections) in children (<18 years) and 63% (n=4,339) (40% influenza, 6% coinfections) in adults. Overall RV detection in children was lower during pandemic years, but increased from 59% (n=17) in 2020-21 (all ORV, 24% coinfections) to 90% (n=308) (82% ORV, 9% SARS-CoV-2, including 32% coinfections) in 2021-22 and 89% (n=361) (84% ORV, 5% SARS-CoV-2, including 32% coinfections) in 2022-23. In adults, overall RV detection was also lower during pandemic years, but increased from 44% (n=333) (3.4% ORV, 40% SARS-CoV2, including 0.9% coinfections) in 2020-21 to 58% (n=731) (14% ORV, 44% SARS-CoV-2, including 3.3% coinfections) in 2021-22 and 50% (n=746) (27% ORV, 23% SARS-CoV-2, including 2.4% coinfections) in 2022-23. No influenza and no RSV were detected in 2020-21; their detection increased in two subsequent years but did not reach pre-pandemic levels. Compared to pre-pandemic period, peaks of RSV hospitalization shifted in 2021-22 (16 weeks earlier), and in 2022-23 (15 weeks earlier). Peaks of influenza hospitalization shifted in 2021-22 (17 weeks later) and in 2022-23 (4 weeks earlier). Age distribution was different compared to pre-pandemic period, especially during first pandemic year (lower proportion of children and higher proportion of older patients). There were significant differences in individual ORV and SARS-CoV-2 detection between time periods and age groups.

Conclusions:

Significant shifts in viral etiology, seasonality, and age distribution of ARI hospitalizations occurred during three pandemic years. Changes in age distribution observed in our study may reflect modifications in the landscape of circulating RV and their contribution to ARI hospitalizations. During the pandemic period, SARS-CoV-2 had a low contribution to pediatric ARI hospitalizations while it was the main contributor of adult ARI hospitalizations during first two seasons and dropped below ORV during the third pandemic season. Evolving RV epidemiology underscores the need for increased scrutiny of ARI hospitalization etiology to inform tailored public health recommendations. Clinical Trial: Not applicable