Subtype-specific associations between ambient air pollution and influenza virus infection: A nationwide...

With the advancement of industrialization and the acceleration of urbanization, air pollution has become a major environmental health issue worldwide. However, the subtype-specific associations between air pollution and influenza virus infection remains unclear. In this nationwide individual-level case-crossover study, conditional logistic regression models combined with distributed lag models were applied to quantify the associations between exposure to PM_2.5, PM₁₀, O₃, CO, NO₂, SO₂ and influenza virus infection in China. From 2013 to 2017, we included 257,763 laboratory-confirmed influenza-positive cases that had residential address information at the street or township level or finer, of which 177,794 (68.98%) were infected by influenza A. Our results indicated that for each 10 μg/m³ increase in PM_2.5, PM₁₀, CO, NO₂, and SO₂, the cumulative 7-day (lag06) effects on influenza virus infection increased by 1.54% (95% CI: 1.33-1.76%), 1.05% (95% CI: 0.90-1.19%), 0.11% (95% CI: 0.10-0.13%), 4.68% (95% CI: 4.10-5.26%), and 4.34% (95% CI: 3.84-4.83%), whereas O₃ showed a significant protective effect, with 10 μg/m³ increase, the cumulative influenza virus infection would decreased by 2.96% (95% CI: 2.60-3.32%). The associations between all six air pollutants and influenza A virus infection were stronger than those for influenza B virus infection. With per 10 μg/m³ increase in PM_2.5 the cumulative 7-day risk of influenza A and B virus infection increased by 1.92% (95% CI: 1.66-2.18%) and 0.75% (95% CI: 0.37-1.13%), respectively. Given the rapid urbanization process in China, our findings support professionals in developing public health policies that balance socioeconomic development with the environmental burden of influenza.