Study On JE Epidemic Characteristic And Forecast Methods With ARIMA In Hebei Province

Objective: To arrange the epidemic data on human epidemic situation of JE in Hebei province from 1950 to 2006,to sample to survey IgG positive rate of healthy population aged 0¹5 in Hebei province in 2007, to analyze epidemic characteristic of JE,to explore diversity rule , to establish feasible forecast method,and to institute the strategy and measure of JE control and prevention.Methods:1 The SPSS13.0 was used to set up the databases on human epidemic situation of JE and healthyy population antibody ,to analyze all the databases , and to establish suitable predictive model of JE epidemic situation and forecast the epidemic situation in 2007.2 To detect healthy population antibody with ELISA-IgG Kit.Results:1 The epidemic situation took on an decreasing tendency in Hebei province,in which the incidence rate descend much higher than that in whole nation. Last century,1950s-1970s,6 times JE epidemic, of which the highest was the year of 1969(incidence rate was 21.56/100 000), have taken place in the whole province. From 1980s to 1990s,incidence rate decreased acute ,and did 0.5/100 000 in the end. From 1950 to 2006, 93539 cases of JE were reported.The epidemic situation indicated a 3-5 years cycle,which was obviously in high incidence rate as era of 50-70,which existed but wave extent decreased in lower incidence rate eras like as 1980s and 1990s ,which was not obviously in lowest incidence rate after 2000. According to the month distribution of JE cases, the epidemic season of JE in Hebei province was from August to September, in which the number of JE cases was 86.36% of the total number. The epidemic season of JE was approximately similar in different districts of Hebei province.In that,summer and autumn are epidemic seasons of JE in Hebei province.2 According to the age distribution, the child was the high risK group in JE epidemic area, the aged 0-15 took up 76.1%(566 cases). The constituent ratio of JE cases at the age groups of 0 and 5 showed a descending tendency,after group 10 showed an ascending tendency,after group 40 did obviously. The sex distribution kept steady state, and the sex proportion was 1.07².67:1,the incidence rate of male and female showed a descending tendency, but the sex proportion showed a ascending tendency. The male average incidence rate was higher than the female. The occupation distribution of JE showed that student,scattered child,peasant,nursed child were higher incidence occupations.The number of student cases was highest,up to 33.08%,the second scattered children ,up to 30.46% .There was not obvious distinct constituent ratio in diffent years.Although student and scattered children were primary ,as to constituent ratio ,peasant appeared increasing tendency .3 The JE was widespread in all the districts of Hebei province,and 11 prefectures had cases.Handan,Tangshan,Baoding,ShiJiazhuang were high incidence prefectures.After 2000 prefecture Xingtai became new epidemic area. The 1950s-1970s, the JE cases were reported in almost all counties(districts).In 1980s vaccine was spread,so the number of counties(districts)which had cases decreased acute,to below 50 after 2000,but rised to above 50 in 2006.Based on geographic setting,the cases number increased from North to South,from West to East.The case high-density counties concentrated in the south of Moutain Yanshan and the Plain of South . There was a characteristic both highly diverging and relative concentration in Hebei province.4 Serum IgG results demonstrated that three groups had difference,group aged 0 was higher 6 and 11¹5. In three groups, the difference between group aged 0 and 11¹5 was significant,other groups were not. There were significant difference between epidemic areas.5 The model ARIMA(1,0,0)×(0,1,1)₁₂ was made to fit the number of JE cases in Hebei province from 1995 to 2006 and forecast the number of JE cases in Hebei province in 2007 as optimization model. The predictive numbers were not equal to the practical numbers, but the practical numbers were all in the 95% confidence interval of corresponding predictive numbers.Conclusions:1 The epidemic situation took on an decreasing tendency in Hebei province,which belonged to low incidence province in the whole nation.Epidemic cycle was obvious before vaccine spread, while incidence rate changed weekly after vaccine used,but summer and autumn were the primary incidence season constantly.2 The children was the high risk group in Hebei province, and student was the major group. The older group incidence range had an enlargement tendency.3 The JE epidemic areas were widespread in Hebei province.It presented a characteristic of both highly diverging and relative concentration before vaccine spread,while it presented a characteristic of diverging after vaccine spread. The high incidence areas concentrated in the south of Moutain Yanshan and the Plain of South all the time,but the intensity of epidemic situation in different epidemic areas was in dynamic state.4 There were a low IgG positive rate of aged 0¹5 healthy population, and IgG positive rate were different between epidemic areas.5 The ARIMA model could be used to make the short-term forecast of JE month cases.