海南省流行性乙型脑炎不同时期流行特征分析

Epidemiological characteristics and related influencing factors on Japanese encephalitis in Hainan province

目的了解海南省不同时期流行性乙型脑炎（乙脑）流行特征及其影响因素。方法收集1952年以来乙脑疫情资料，按照乙脑自然流行期（1952—1978年）、推广使用乙脑灭活疫苗期（1979—1986年）、计划免疫使用乙脑灭活疫苗期（1987—1990年）、计划免疫使用乙脑减毒活疫苗期（1991--2007年）四期分析乙脑发病率、死亡率、病死率、乙脑疫苗接种率、病例免疫史、病例及媒介监测等资料，分析影响因素。结果海南省不同时期中以乙脑自然流行期年均发病率最高为7．12／10万，死亡率0．89／10万；推广使用乙脑减毒活疫苗期年均发病率最低为0．11／10万，死亡率0．01／10万。海南省于2002年开始建立乙脑监测系统以来，监测报告乙脑疑似病例标本采集率达到92．8％，确诊病例发病率波动在0．05／10万-0．2／10万之间，确诊病例中86％无明确乙脑疫苗免疫史；2004-2007年乙脑疫苗年均保护率为95．69％。海南省媒介密度高，宿主动物中猪乙脑感染率从4月持续到10月呈上升趋势，个别监测点感染率高达99．3％，媒介密度和宿主动物感染呈反向曲线分布。结论海南省应用乙脑减毒活疫苗对保护易感儿童，降低乙脑发病率，控制流行取得了显著的效果。

Objective To understand the epidemiological characteristics and the influencing factors of Japanese encephalitis （Abbreviated JE） at different periods in Hainan province, and to provide evidence for JE control strategies. Methods Data on JE had been collected since 1952 and related incidence, mortality, fatality rates of JE and the rate of JE vaccination were calculated for four periods： the natural epidemic period （1952- 1978）, period for inactivated JE vaccine promotion （1979- 1986）, national immunization program period （ 1987 - 1990） and the promotion of live-attenuated JE vaccine period （ 1991 -2007）. History on the immunity of JE and data from the monitoring programs on cases and insect vectors were also analyzed. Results The average annual incidence in natural epidemic period was 7.12/100 000, which was also the highest among the 4 periods with the mortality rate as 0.89/100 000. The average annual incidence was 0.11/100 000 which was the lowest while the mortality rate was 0.01/100 000 in the period when live-attenuated JE vaccination was under promotion. Since the establishment of JE surveillance system was set up in Hainan province in 2002, the specimen collection rate of JE reported suspected cases had reached 92.8%, while the incidence of confirmed JE cases fluctuated between 0.05/ 100 000 and 0.2/100 000. Of the confirmed cases, 86% did not have clear history of JE vaccination. The annual average protective rate reached 95.69% in 2004--2007. The density of insect vectors was high in Hainan province. The infection rate of JE in host animal swine, kept rising from April to October, and in some surveillance points, the rate reached 99.3%. The density of insect vector plotted in trans-curve with the infection of host animals. Conclusion The application of live-attenuated JE vaccine was found to have had significant protective effect on JE in susceptible children. It helped reducing the incidence and controlling the epidemics of JE. It appears feasible to include live-attenuated JE vaccine into the expanded immunization program.