Association between ozone and influenza transmissibility in China

Common air pollutants such as ozone (O₃), sulfur dioxide (SO₂), nitrogen dioxide (NO₂), and particulate matter play significant roles as influential factors in influenza-like illness (ILI). However, evidence regarding the impact of O₃ on influenza transmissibility in multi-subtropical regions is limited, and our understanding of the effects of O₃ on influenza transmissibility in temperate regions remain unknown.

We studied the transmissibility of influenza in eight provinces across both temperate and subtropical regions in China based on 2013 to 2018 provincial-level surveillance data on influenza-like illness (ILI) incidence and viral activity. We estimated influenza transmissibility by using the instantaneous reproduction number ([Formula: see text]) and examined the relationships between transmissibility and daily O₃ concentrations, air temperature, humidity, and school holidays. We developed a multivariable regression model for [Formula: see text] to quantify the contribution of O₃ to variations in transmissibility.

Our findings revealed a significant association between O₃ and influenza transmissibility. In Beijing, Tianjin, Shanghai and Jiangsu, the association exhibited a U-shaped trend. In Liaoning, Gansu, Hunan, and Guangdong, the association was L-shaped. When aggregating data across all eight provinces, a U-shaped association was emerged. O₃ was able to accounted for up to 13% of the variance in [Formula: see text]. O₃ plus other environmental drivers including mean daily temperature, relative humidity, absolute humidity, and school holidays explained up to 20% of the variance in [Formula: see text].

O₃ was a significant driver of influenza transmissibility, and the association between O₃ and influenza transmissibility tended to display a U-shaped pattern.