Objective To quantify the short-term impact of air pollutants on influenza-like illness (ILI) occurrence in Yichang, and to provide scientific reference for the prevention and control of influenza in the area.
Methods The daily data of air pollutants (PM2.5, PM10, SO2, CO, NO2, and O3), temperature, and ILI from two sentinel hospitals in Yichang during 2014 and 2016 were collected. A distributed lag non-linear model (DLNM) was used to analyze the excess risk (ER) and lag effect of various air pollutants on the incidence of ILI. Moreover, stratified analyses by age and season subgroups were conducted; the seasonal stratification was tested by q values in geographical detector.
Results There were totally 30 090 ILI cases reported in Yichang from 2014 to 2016. For PM2.5, PM10, and CO, the strongest effects on daily ILI cases were observed on lag 0 day, with ER (95%CI) of 0.78% (0.31%-1.26%), 0.56% (0.20%-0.92%), and 1.08% (0.29%-1.88%), respectively; and the effects of NO2 and O3 were strongest on lag 1 day with ER (95%CI) of 2.29% (0.34%-4.25%) and 0.45% (0.03%-0.88%), respectively. A 10 μg/m3 increase in PM2.5, PM10, NO2, and O3 and a 0.1 mg/m3 increase in CO were associated with 1.08%, 0.82%, 4.95%, 1.44% and 1.95% increases of cumulative ILI cases, respectively. SO2 only statistically affected the incidence of the group of 5-14 years with a cumulative ER of 11.86% (95% CI:5.06%-19.11%); a 10 μg/m3 increase in PM2.5, NO2, and O3 and a 0.1 mg/m3 increase in CO were associated with 1.41%, 6.29%, 2.38%, and 2.88% increases of cumulative ILI cases in residents aged 25-59 years, respectively; a 10 μg/m3 increase in PM2.5, PM10, and NO2 and a 0.1 mg/m3 increase in CO were associated with 1.56%, 1.24%, 8.02%, and 4.24% increases in cumulative ILI cases in the residents with age ≥ 60 years, respectively. In spring, a 10μg/m3 increase in PM2.5 and PM10 was associated with 3.66% and 2.02% increases of cumulative ILI cases, respectively. In summer, a 10μg/m3 increase in O3 was associated with 3.25% increase of cumulative ILI cases. In autumn, a 10μg/m3 increase in PM2.5 and PM10 were associated with 3.15% and 2.92% decreases of cumulative ILI cases, respectively. In winter, the effects of various air pollutants on ILI cases were not statistically significant.
Conclusion All the air pollutants studied have short-term effects on the occurrence of ILI, which is varied by age groups and seasons.
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