Introduction

Following opening of lockdown and relaxation of public health restrictions, unusual surge of respiratory illness occurred during the spring/summer (Q2) 2021 season. We aimed to characterize thissurge compared to previous years.

Methods

Children discharged from a single tertiary hospital for respiratory illness or selected non-communicable diseases between 2015- 2021 were included, and hospitalization rates were compared. To evaluate whether the current respiratory surge resembles a typical winter, characteristics of the second quarter (Q2,April-June) of 2021 were compared to parallel seasons and to autumn/winter (Q4, October-December) of previous years.

Results

Respiratory illness showed a seasonal peak, while the pattern of noncommunicable disease was consistent throughout the study period. Respiratory illnesses showed a delayed surge in Q2 2021 (389 patients), with a missing seasonal peak in Q2 and Q4 2020 (135 and 119 patients, respectively). There were more cases of croup in Q2 2021 compared to Q2 and Q4 2015-2019 (26.2 vs. 12.5 and 15.8%, p<0.001), fewer cases of pneumonia (5.9 vs. 15.9 and 11.7%, p<0.001), lower admission rates (22.4 vs. 36.3 and 31.5%, p<0.001), and fewer hypoxemia during hospitalization (6.3 vs. 11.7 and 10%, p<0.001). Additionally, lower use of antibiotics (6.2 vs. 12.3 and 10.3%, p=0.001 and 0.012 respectively) and higher use of steroids (33.7 vs. 24.8 and 28.3%, p<0.001 and 0.034 respectively).

Conclusions

The postponed increase in respiratory morbidity after lockdown had unique characteristics, with upper respiratory illness predominating and fewer hospitalizations. Follow-up is needed to assess the altered epidemiological patterns of respiratory diseases in the post-COVID era.

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