PURPOSE: Studies have demonstrated important changes in the seasonality of pediatric respiratory illnesses since the onset of the COVID-19 pandemic. The aim of this study was to describe the epidemiology of childhood wheezing episodes before and after the start of the COVID-19 pandemic in relation to their potentially associated environmental triggers.

METHODS: Files of all children treated with salbutamol for an acute wheezing episode in September and October 2019, 2020, and 2021 were retrospectively reviewed. Infection epidemiology, daily concentrations of air pollutants (NO, O, PM, and PM), and fungal spores were collected over the same time period.

RESULTS: In 2021, 298 episodes of wheezing were observed compared to 111 in 2020 and 86 in 2019 (p < 0.001). Compared to 2019, children with wheezing in 2021 were significantly older (p < 0.001), less likely to have a history of recurrent wheezing (p < 0.001) and required less hospitalization (p = 0.034). Adenovirus and SARS-CoV-2 were more prevalent in 2021 as compared to 2019 (p < 0.001). The concentration of PM, PM, and O was higher in 2021, as compared to both 2019 and 2020 (p < 0.001) while the concentration of NO and airborne spores was lower in 2021 compared to 2019 (p < 0.0001).

CONCLUSION: A threefold increase in wheezing episodes was observed in the autumn post-COVID (2021) compared to pre-COVID (2019) together with very high circulation of SARS-CoV-2 and a significant increase of PM, PM, and O