| Objective:To quantitatively analyze the short-term impact of air pollution on influenza-like illness occurrence in Yichang,so as to provide scientific reference for the prevention and control of influenza in the area.Methods:The daily surveillance data of air pollutants(PM2.5,PM10,SO2,CO,NO2 and O3),meteorological factors and influenza-like illness?ILI?in Yichang during 2014-2017 were collected.First,a distributed lag non-linear model?DLNM?was used to analyze the effect of meteorological factors on ILI.And then temperature and humidity was brought into the pollutant model as correction factors.After parameters were determined,excess risk?ER?and lag effect caused by every air pollutant on the incidence of ILI were analyzed.Moreover,stratified analysis by age groups and seasons were conducted.The seasonal stratification was tested by geographical detector.Results:1.There were totally 45130 ILI cases in Yichang during 2014 to 2017.30.50%of these cases occurred among 25-59 age group,with a total of 13766 cases.24.21%,22.96%and 12.78%of all cases occurred for age groups of 0-4,15-24 and over 60,Which were 10928 cases,10361cases and 5766 cases,respectively.A total of 4863cases occurred among 5-14 age group,accounting for 10.78%.Influenza in Yichang occurred all year round,and there were small peaks in summer and winter seasons.2.During 2014-2017,the daily average concentration trends of PM2.5,PM10 and CO showed a unimodal pattern,with annual peaks in winter and low in summer.The concentration trend of NO2 was bimodal,with low valleys in February and August-September,and peaks in April-May and December-January.The seasonal character of O3 concentration was high in summer and low in winter.In 2014,the daily average concentration of SO2 was significantly higher than that of other years.In May of the following year,there was a significant decrease,and then it remained at a low level.The seasonality was not obvious.The average daily temperature was very regular.The peak was from July to August every year,and the lowest point was in January-February.The daily average relative humidity did not show periodicity,mainly fluctuating between 50%and 99%.3.Temperature and relative humidity had effects on ILI.Low temperature was a risk factor for ILI.When the temperature was lower than the reference temperature of25°C,the temperature was lower,and cumulative RR value would be larger,which meant bigger risk of ILI.High temperature had no statistically significant risk for ILI.High humidity caused an increase in ILI.When the average daily relative humidity reached 85%and above,the cumulative RR value would increase with the increase of relative humidity.The effect of low humidity on ILI has no significance.4.During 2014-2017,the cumulative ER values of PM2.5,PM10,and CO on ILI were 1.13%?0.26%-2.00%?,0.81%?0.16%-2.00%?,and 2.60%?1.43%-3.79%?,respectively.For PM2.5,PM10 and CO,the strongest effects on daily ILI cases were observed on lag0.The effects of PM2.5 and PM10 on ILI were statistically significant on lag6-9.The increase of CO concentration had a significant effect on ILI on lag4-8.On lag8-10d,the increase of SO2 concentration was risk factor for ILI.There was a negative correlation between NO2 and ILI on lag4-5d.The increase of O3 had no statistically significant effect on ILI during 10 days.5.Only the increase of O3 concentration had a statistically significant effect on ILI in people aged 0-4.For people aged 5-14,a 10?g/m3 increase of SO2 was associated with 13.87%increase of ILI cases and there was a negative correlation between NO2and ILI.A 0.1 mg/m3 increase of CO would resulted in 3.72%?1.72%-5.75%?and 5.85%?3.30%-8.45%?increase of ILI cases in people aged 25-59 and over 60 years old,respectively.6.In spring,the effect of PM2.5.5 on ILI was 1.48%?0.50%-2.48%?and 0.62% ?0.01%-1.22%?on lag0-1.The increase of PM10 was a risk factor for the increase of ILI on lag0,and the ER value was 0.71%?0.09%-1.32%?.On lag0-1 and lag4,the increase of CO had a significant effect on ILI.In summer,an increase of 10?g/m3 in O3 was associated with 0.71%?0.03%-1.40%?increase of ILI.In winter,some air pollutants had negative effects on ILI on several lag days such as PM2.5 on lag3,PM10 on lag3-4d,CO on lag1-3d and NO2 on lag5-6d.Conclusions:During 2014-2017,all the air pollutants had significantly short-term effects on the occurrence of ILI with lag effect and cumulative effect.The single-day effect of air pollutants was largest on lag0,and then there was a lagged effect on lag5-9.Different pollutants had different effects in age groups and seasons. |
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