ABSTRACT
Objective To describe the epidemiologieal features of viral encephalitis and burden of Japanese encephalitis (JE),and to identify potential strategies for effective JE control measures,using data from the Viral Encephalitis Surveillance Program (VESP) launched in Ankang,Baoji,and Weinan prefectures,Shaanxi province.Methods Data was gathered from sentinel hospitals reporting system on all the viral encephalitis (VE) eases identified between June 2005 and May 2007.County Center for Disease Control and Prevention (CDC) investigated the cases,drawing blood and cerebrospinal fluid (CSF) samples from the hospitals,and testing IgM antibody against JE using ELISA.We used Epi Data and Excel for data entry and analysis.Results A total of 1097 VEs were reported and 1053 (96.0%) had blood or CSF samples collected and tested for IgM antibody against JE.Three hundred and eleven cases (29.5%) showed JE antibody positive (JE confirmed case).Among the JE confirmed cases,numbers of those under 15 year of age accounted for 33.7%,43.9%and 88.3%in Baoji,Weinan and Ankang prefectures respectively.The rest were mainly children aged 5-14 years old (53.3%).Toddlers,farmers and children accounted for 85.2%in JE confirmed cases.About half of other VE cases (51.0%) were students of all age.Data an investigation on 398 reported VE cases at discharge,showed that 67.1%of JE confirmed cases recovered while 83.7%of the other VE cases fully recovered.The case fatality rates were 9.2%for JE confirmed cases and 3.1%for other VE cases.578 cases were followed up at 90-days after discharge,69.6%of JE confirmed cases and 90.2%of other VE cases recovered,with case fatality rates were 13.6%and 3.6%for JE confirmed cases and for other VE cases,respectively.The sequelae rates were 10.0%for JE confirmed cases and 4.5%for other VE cases.Conclusion The peak of the VE season was the sameas that of JE.There were 45.6%of reported JE cases with negative JE IgM,suggesting that it is necessary to carry out laboratory testing for clinical diagnosis cases.The fact that high risk population was different at prefectures levels suggested that more attention be paid in JE control and prevention.