Short-term Effects Of Meteorological Factors On The Incidence Of Varicella In Lu’an From 2015 To 2020

Objectives:Under the background of global climate change,the purpose of this study is to clarify the epidemic characteristics and occurrence regularity of varicella in Lu’an City,Anhui Province,and to explore the relationship between various meteorological factors and the risk of varicella.At the same time,the differences of exposure-lag effects of meteorological factors on varicella in different gender and age subgroups were compared,and the potential meteorological factors affecting the incidence of varicella were further revealed.Thus,it provides new ideas for formulating scientific and effective measures for prevention and control of varicella and improving the construction of early warning system.Methods:The surveillance data of varicella incidence in Lu’an City from January 1,2015 to December 31,2020 were obtained and collated by National Notifiable Diseases Reporting System（NNDRS）.Descriptive epidemiological methods were used to describe and analyze the epidemic characteristics of varicella,in order to reveal the frequency and distribution of varicella cases in different time,population and area,and to identify the epidemic season,key population and high incidence area.The daily data of meteorological factors and air pollutants during the study period were obtained from China Meteorological Data Network and national air quality monitoring stations in Lu’an.Then a time series database was established,and Spearman rank correlation analysis was used to test the correlation among varicella cases,meteorological factors and air pollutants.Poisson regression was implemented by generalized additive model（GAM）,and distributed lag nonlinear model（DLNM）was built,to quantitatively analyze and evaluate the exposure-lag effects of various meteorological factors on varicella incidence,and the risk of varicella in extreme meteorological conditions,while controlling for the influence of potential confounders such as other meteorological factors,air pollutants,long-term trends,seasonal patterns,day of the week effects and holiday effects.In addition,grouping analysis was performed for gender（male,female）and age（0-5 years,6-17 years,≥18 years）to explore differences among different subgroups.Finally,the stability of the models was evaluated through a series of sensitivity analysis.Results:（1）A total of 15968 varicella cases were included for analysis from 2015 to2020.The results showed that varicella incidence showed an overall trend of rising and then falling,with a peak in 2019 followed by a rapid decline.The seasonal pattern showed a bimodal distribution with an annual cycle,with a small peak from May to June and a large peak from October to January.The average annual reported incidence of varicella was 56.19/100000,and the incidence of varicella in male（64.85/100000）was higher than that in female（47.12/100000）,and that in Huoshan County was higher than that in other areas.In terms of population distribution,the ratio of male to female was 1.44（9426 cases to 6542 cases）.The age of high incidence was mainly 0-17 years old,accounting for 80.83%（12907 cases）.Most of cases were students,scattered children and kindergarten children,accounting for 67.80%（10826 cases）,9.71%（1551cases）and 9.00%（1437 cases）,respectively.In addition,we observed that the average number of daily varicella cases in Lu’an was 7.28,higher in male（4.30 cases）than in female（2.98 cases）,and higher in the school-age group of 6-17 years（4.70 cases）than in the group of preschool children aged 0-5 years（1.19 cases）and the adult group of≥18 years（1.40 cases）.The average values of mean temperature（MT）,diurnal temperature range（DTR）,mean air pressure（MP）,wind speed（WS）and sunshine hours（SH）were 16.89°C,8.17°C,1007.38 h Pa,1.79 m/s and 4.66 h,respectively.The daily average concentrations of PM_2.5,PM₁₀,SO₂,NO₂,CO and O₃ were 45.04,75.39,9.39,30.28,739.64 and 91.56μg/m³,respectively.（2）Overall effect of varicella incidence:during the maximum lag period of 0-21 days,the effects of both MT and MP on varicella showed W-shaped curve relationship,peaked at 17.5℃（RR=2.085,95%CI:1.480-2.937）and 1035.5 h Pa（RR=5.481,95%CI:1.813-16.577）,respectively;the effect of DTR showed an M-shaped curve and peaked at 4.4℃（RR=6.131,95%CI:1.120-33.570）;there was no significant correlation between WS and the risk of varicella;and the overall risk of varicella increased significantly at the lag of 0-8 days and 0-9 days,when SH exceeded 10 hours.Single-day lag effect of varicella incidence:when MT was-5.8℃,the maximum risk of varicella in the total population was 1.288（95%CI:1.201-1.381,lag 16 day）,and subgroup analysis showed that the risk of varicella incidence was greatest in the school-age group of 6-17 years,followed by males,who were sensitive to low temperature conditions.When DTR was 13.5℃,the maximum risk of varicella in the total population was 1.475（95%CI:1.152-1.889,lag 0 day）,and subgroup analysis showed that the greatest risk of varicella was found in the group of preschool children aged 0-5 years,followed by females,who were a sensitive population in the presence of large diurnal temperature changes.When MP was 1035.5h Pa,the maximum risk in the total population was 1.307（95%CI:1.196-1.427,lag 16 day）,and subgroup analysis showed that the risk of varicella incidence was greatest in the school-age group of 6-17 years,followed by male,who were sensitive to high pressure conditions.When WS was 6 m/s,the maximum risk in the total population is 1.271（95%CI:0.981-1.647,lag 4 day）,but the risk of varicella in the total population,gender and age subgroups was not statistically significant.When SH were 0 hours,the maximum risk of varicella in the total population was 1.266（95%CI:1.162-1.378,lag 21 day）,and subgroup analysis showed that the risk of varicella was greatest in the school-age group of 6-17 years,followed by male,who were the sensitive population when there was no sunlight exposure.In addition,except for the extremely high wind speed,the lag effects of extreme meteorological factors on varicella cases were statistically significant.The results of sensitivity analysis were stable.Conclusions:During the lag period,daily mean temperature,mean air pressure,DTR,and sunshine hours had significant nonlinear and lag effects on varicella incidence in Lu’an City.Exposure to low and high temperatures,low levels of DTR,high pressure,and prolonged sunshine all significantly increased the overall risk of varicella.The group of preschool children aged 0-5 years and females were more sensitive to diurnal temperature differences,while the school-age group of 6-17 years and males were more sensitive to mean temperature,mean air pressure and sunshine hours.Our findings suggest that meteorological factors may play a key role in the occurrence and spread of varicella in Lu’an,and provide evidence for using local meteorological monitoring data to predict disease risk,which is helpful for improving early warning systems and effectively controlling varicella outbreaks.