OBJECTIVETo analyze the prevalence trend, prevalence characteristics and influence factors of Japanese B Encephalitis (JE) in Henan province.

METHODSThe data that of 64 401 JE patients in Henan from 1980 to 2008 were statistically analyzed by SPSS12.0 and EXCEL2003 software. Luoshan, Xinan, Xihua, Deng county and Hua county were chosen as monitoring sites. The mosquito specimens were gathered with the artificial hour method and the mosquito curtain method, the mosquito density was calculated one time each ten day period from May to July. At the same time, 30-40 newborn pig blood samples were gathered each ten-day period and the pig serum JE IgG antibody was detected by ELISA method.

RESULTSThe Cumulative incidence of JE was 64 401 cases in Henan province from 1998 to 2008, the range of incidence rate was from 0.34/100 000 (315/93 599 969) to 6.72/100 000 (5246/78 076 567); The average incidence of JE was 4.39/100 000 (3530/80 381 469) from 1980 to 1994; The average incidence of JE was 0.86/100 000 (811/94 217 549) from 1995 to 2008; In 2008, the incidence rate reached the lowest point for 0.34/100 000 (315/93 599 969); The incidence occurred mainly in July-September, accounting for 89.40% of the total cases (57 572/64 401); the patients were concentrated mainly in 5 cities, which were Xinyang, Nanyang, Zhumadian, Zhoukou, Luoyang, accounting for 81.02% (52 175/64 401). The 0 - 14 years old age group was the dominant group (79.01%, 50 884/64 401). In Luoyang city, incidence of >/= 15 years old group was significantly increased (57.83%, 2120/3666), the constitution of JE incidence were significantly different between 0 - 14 years old group and >/= 15 years old age group (chi(2) = 2705.32, P < 0.05) in Henan province and Luoyang city. The different density of the mosquitoes and the different positive-times for 50% of the antibodies of JE in piglets on the monitor sites showed the intensity of JE disease.

CONCLUSIONThe incidence of JE showed a decreasing trend, seasonal, regional characteristics and age distribution difference in Henan province. The monitoring of host animal pig JE antibody level and the medium mosquito density may forecast the JE prevalence tendency. To control the incidence in the younger groups in Henan province, older age group in Luoyang city and high-incidence areas, it is important to strengthen the monitoring and forecasting measures to prevent JE in Henan province.