The Analysis On Seasonal Influenza Epidemic Characteristics And Meteorological Driving Factors In Guilin City

Objectives:1.To describe the surveillance results of influenza in Guilin City during the 2013-2019 surveillance years,and analyze epidemic trend and epidemic intensity.2.To quantitatively evaluate the threshold and lag effects of meteorological factors on laboratory-confirmed influenza cases and different types of influenza in Guilin City.3.To explore the interaction of meteorological factors on the laboratory-confirmed influenza cases in Guilin City.Methods:1.During April 1,2013 to March 31,2019,ILI,etiological monitoring data and meteorological data were collected and analyzed by descriptive epidemiological methods.2.The MEM was used to formulate the epidemic intensity threshold of 2018-2019,and the application effect was evaluated by using the sensitivity,specificity and Jordan index.3.Spearman correlation was used to analyze the correlation between meteorological factors,and meteorological factors and laboratory-confirmed influenza cases.4.The DLNM model was used to explore the threshold and lag effects of meteorological factors on influenza.The GAM model was used to explore the interaction between meteorological factors.Results:1.The ILI%of Guilin sentinel hospitals in 2013-2019 was 3.96%,and the difference in ILI%reported in each monitoring year was statistically significant(x2=24,007.67,P<0.001).The number of ILI cases was the largest among people aged 0-4 years,followed by the age group of 5-14 years.During the study period,the positive rate of ILI specimen test in Guilin network laboratory was 14.94%.The difference of positive rate in each monitoring year was statistically significant(x2=226.19,P<0.001)).During the study period,the epidemic status of dominant influenza viruses varied from year to year,and all the seasonal influenza subtypes were detected and alternately dominant.The MEM results showed that the pre-epidemic threshold and post-epidemic threshold of the 2018-2019 were 20.04 and 12.63,respectively;the three intensity thresholds of medium,high,and very high were 32.66,50.92,and 61.96,respectively,and the model applied well in general.2.The average temperature,absolute humidity and sunshine hours during the study period were negatively correlated with laboratory-confirmed irfluenza cases(P<0.01);relative humidity,average air pressure and rainfall were positively correlated with laboratory-confirmed influenza cases(P<0.05).3.Taking the median of each meteorological factor as a reference value,each meteorological factor has a non-linear lag pattem with the number of laboratory-confirmed influenza cases.The overall cumulative cumulative lag effect results show that low temperature(<22℃),high relative humidity(>79%),lower(7mb～11mb)or higher(17mb～23mb)absolute humidity,high atmospheric pressure(>1018 hpa),rainfall(>0mm),shorter(0h～2h)or longer(8h~9h)sunshine hours can increase the nsk of flu.In terms of the cumulative effect of specific meteorological variables,the cumulative effect of low temperature(7℃)was delayed and lmted for a long time,and the cumulative RR was 3.54(95%CI:1.75～7.16).The cumulative effect of high temperature(30℃)peaked at lag 1d with the cumulative RR value of 1.46(95%C1:1.13～1.88),and then decreased rapidly.The cumulative effects of low relative humidity(46%)and high relative humidity(93%)were short,and the maximum cumulative RR value were at lag 5d(RR=1.36,95%CI:1.02～1.82)and 14d(RR=1.68,95%CI:1.15～2.44).The cumulative effects of low absolute humidity(8mb)and high absolute humidity(22mb)both reached their peaks at the lag 2ld,with cumulative RR values of 2.10(95%C1:1.13～3.83)and 2.22(95%C1:1.30～3.83),respectively.The cumulativ e effect of high pressure(1020hpa)lasted for a short time,and the cumulative RR value was 14.10(95%CI:1.23～161.64)at lag 16d.The cumulative effect of high rainfall(34mm)lmted for a long time,and the cumulative RR value was 2.85(95%CI:1.68～4.84)at lag 14d.The cumulative effect of short hours of sunshine(Oh)and relatively long hours of sunshine(8h)lasted for a long time,and the cumulative RR values were the highest at lag 2ld,which were 2.95(95%CI:1.43～6.09)and 4.10(95%CI:1.72～9.78),respectively.The influence of different meteorological factors on the incidence of different types of influenza is different.Low temperature and high relative humidity are the risk factors for FluA and FluB.Absolute humidity,air pressure,rainfall,and snshine hours mainly affect FluA.Conclusions:1.The peak of influenza activity in Guilin City is mainly concentrated in summer and winter and spring every year.People aged 0 to 4 years are high-risk groups for the onset of influenza,followed by the age group of 5 to 14 years.2.Each meteorological factor presented a nonlinear lag mode with the number of laboratory confirmed influenza cases.Low temperature(<22℃),high relative humidity(>79%),lower(7mb～11mb)or higher(17mb～23mb)absolute humidity,high atmospheric pressure(>1018 hpa),rainfall(>0mm),shorter(0h～2h)or longer(8h～9h)sunshine hours can increase the risk of influenza in Guilin City.3.There was an interaction between temperature and relative humidity,temperature and rainfall,absolute humidity and sunshine hours,relative humidity and atmospheric pressure.