Change in disease burden associated with influenza and air pollutants during the COVID-19 pandemic in Hong Kong

Objectives: This study aimed to estimate the variation in disease burden associated with air pollutants and other respiratory viruses during the COVID-19 pandemic. Methods: We adopted a machine learning approach to calculate the excess mortality attributable to air pollutants and influenza, during the pre-pandemic and pandemic period. Results: In the first 2 years of the COVID-19 pandemic, there were 8762 (95% confidence interval, 7503–9993), and 12,496 (11,718–13,332) excess all-cause deaths in Hong Kong. These figures correspond to 117.4 and 167.9 per 100,000 population, and 12.6% and 8.5% of total deaths in 2020 and 2021, respectively. Compared to the period before the pandemic, excess deaths from all-causes, cardiovascular and respiratory diseases, pneumonia and influenza attributable to influenza A and B significantly decreased in all age groups. However, excess deaths associated with ozone increased in all age-disease categories, while the relative change of nitrogen dioxide (NO₂) and particular matters less than 10 µm (PM₁₀) associated burden showed a varied pattern. Conclusions: A notable shift in disease burden attributable to influenza and air pollutants was observed in the pandemic period, suggesting that both direct and indirect impacts shall be considered when assessing the global and regional burden of the COVID-19 pandemic.