| Japanese encephalitis(JE),is one of category B infectious disease under the control of Law of the People’s Republic of China on prevention and control of infectious diseases.After being bitten by mosquitoes carrying JE virus,most people show symptoms of recessive infection with no special clinical manifestations,but a few of the patients with overt infection will show clinical symptoms such as high fever,impaired consciousness,convulsions,pathological reflexes and meningeal irritation signs,leaving serious sequelae.Moreover,JE is characterized by rapid onset,rapid course and high mortality,and its prevention and control is very important.This study focused on the eight northern provinces(Gansu,Ningxia,Shaanxi,Shanxi,Hebei,Beijing,Tianjin,and Liaoning),which are located at the edge of the JE epidemic area.In addition,this region’s high precipitation and temperature in summer and autumn are very suitable for the survival of the main vector of JE,the Culex tritaeniorhynchus.JE cases in this region were also concentrated from July to September,with obvious seasonality.The majority of cases in this region are among adults,especially those over 45 years of age,those people has not been vaccinated,and their immunity decreases with age,increasing the probability of JE.Furthermore climate change has caused global warming,increased extreme weather events,increased precipitation,etc.,coupled with the low population immunity in this region,there are a large number of susceptible people,the combined effect of these factors may lead to the occurrence of JE outbreak in the above-mentioned low-prevalence areas,causing serious consequences.Methods:In this study,the data of JE cases from 2005 to 2019 in eight provinces in northern China were collected through the national notified infectious diseases reporting information system.The data of Cx.tritaeniorhynchus from national vector surveillance data were collected,and the meteorological data of the same period were collected from national meteorological data network.1.The use of Excel 2016 software for JE cases data and drawings.The epidemiological characteristics of JE were analyzed retrospectively.SPSS 22.0 software was used for χ2 test,and ArcGIS 10.2 software was used to draw statistical map of reported cases.2.The use of Excel 2016 software for mosquito surveillance data and drawings.SPSS 22.0 software was used to analyze the correlation between mosquito density and meteorological factors,and ArcGIS 10.2 software was used to draw the distribution map of mosquito vector monitoring points.3.Reports of JE in 8 provinces in northern city of 64,using Spatial Dubin Model(SDM),the analysis of meteorological factors and JE of time and space distribution relationship between reported cases.Results:1.The average annual incidence rate of JE in the study area from 2005 to 2019 was 0.141/100,000,with 390 deaths and a morbidity rate of 7.25%.The distribution of JE expanded from 157 districts and counties in 2005 to 254 districts and counties in 2018.81.26%of the total incidence of JE in August-September was the peak month of JE incidence.the percentage of the 0-14 years age group decreased from 54.55%(2005)to 3.96%(2019),and the percentage of the ≥15 years age group increased from 45.18%in 2005 to 96.03%in 2019(χ2 trend=998.524,P<0.001).Farmers,children in early childhood care and diaspora and students accounted for 58.76%,14.81%and 12.38%,respectively,and the proportion of farmers increased from 37.19%(2005)to 79.21%(2019),which is the occupational group that needs the most attention.2.The monitoring data of the JE vector Cx.tritaeniorhynchus showed that among the mosquitoes monitored in the six northern provinces of Gansu,Shaanxi,Shanxi,Beijing,Tianjin and Liaoning in 2006-2018,Cx.tritaeniorhynchus accounted for 3.94%of the total number of all mosquitoes,and the peak density of mosquitoes in the six northern provinces was July-August each year,and the peak density of Cx.tritaeniorhynchus basically overlapped with the peak density of mosquitoes in July-September.September.The density of Cx.tritaeniorhynchus is significantly higher in two types of rural habitats,such as livestock sheds and farms,than in three types of urban habitats,such as residential areas,parks and hospitals.The density of Cx.tritaeniorhynchus was influenced by monthly mean temperature,monthly mean air humidity and monthly precipitation,and the correlation coefficient between Cx.tritaeniorhynchus and JE cases was 0.475(P<0.001).3.Meteorological factors and case distribution are globally spatially autocorrelated,Moran index is greater than 0 and significant,and the number of days with annual daily precipitation>0.1 mm not only has an impact on local JE cases but also on surrounding areas,with direct and indirect effects.The average annual 2 min wind speed,the average annual maximum temperature,and the number of days with annual daily precipitation ≥0.1 mm had positive effects on the distribution of JE cases,and the indirect effects showed that the number of days with annual daily precipitation>0.1 mm had positive effects on the number of JE cases in the surrounding cities,while the number of days with annual daily precipitation ≥0.1 mm in the surrounding areas also had effects on the number of local JE cases.Conclusion:1.The risk of morbidity increases in higher age groups,and immunization,monitoring and management of higher age groups should be strengthened to prevent epidemic outbreaks.There is a higher incidence among farmers,and there is a special need to carry out health promotion and education in rural areas,to carry out patriotic health campaigns focusing on mosquito control and elimination of mosquito breeding sites,to popularize the knowledge of vaccination and mosquito prevention and control,to improve agricultural mechanization,and to reduce the contact between mosquitoes and the population.July-September is the peak of incidence,and the transmission route should be cut off and mosquito control should be carried out before the peak season comes To reduce the risk of infection.2.Rural areas of farm and livestock sheds should be the focus of mosquito control,livestock sheds in the highest density of Cx.tritaeniorhynchus,should be the key control habitat;hospitals and residential areas habitat and people’s lives are closely related,should strengthen the mosquito control work in such habitats.3.For areas where JE is distributed,the greater the annual average 2 min wind speed,the annual average maximum temperature and the annual daily precipitation ≥0.1 mm days,the higher the risk of JE incidence,and the increased precipitation in the surrounding areas will also increase the risk of JE incidence in the region,which should be taken seriously. |
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