ABSTRACT
Objective The aim is to describe the epidemiological characteristics of Japanese encephalitis(JE) in Sichuan Province from 2008 to 2018, to build time series autoregressive integrated moving average(ARIMA) model, and to discuss the model application in the prediction of JE incidence trends. Methods Descriptive epidemiological analysis was used to analyze the epidemic situation of JE in Sichuan Province from 2008 to 2018. Monthly surveillance data of JE in Sichuan Province from January 2008 to December 2017 were used to fit ARIMA model. The number of reported cases from January to December in 2018 was used to test the model. Results The epidemic situation of JE in Sichuan Province from 2008 to 2018 showed a downward trend, and eastern and southern areas were the highly prevalent areas. The incidence peak was from July to September every year. Children were the high-risk group, but the incidence of adolescent and adult was on the rise in recent years. ARIMA(1,0,0)(2,1,0)12 could appropriately fit the time series. Conclusion ARIMA model can be used for short-term prediction of the reported incidence of JE in Sichuan Province.
ABSTRACT
<p><b>OBJECTIVE</b>To understand molecular characteristics of Japanese encephalitis virus (JEV) isolated from the major Japanese encephalitis epidemic areas in Sichuan Province, and to provide the foundation for JEV prevention.</p><p><b>METHODS</b>13 JEV strains were isolated from mosquitoes in Sichuan during 2007-2010, E genes and preM genes were sequenced and phylogenetic analyses were performed using MEGA5 molecular software.</p><p><b>RESULTS</b>Phylogenetic analysis indicated that all 13 JEV strains from Sichuan belonged to genotype I, homologies at nucleotide level and deduced amino acid level in PreM gene were 97%-100% and 98.7%-100%, and 97.8%-99.9% and 99.6%-100% in E gene, respectively. Homologies at nucleotide level and deduced amino acid level in PreM gene between 13 JEV strains and JEV isolated in 2004 in Sichuan were 96.2%-99.1% and 97.5%-98.7%, and were 97.7%-99.6% and 98. 6%-100% in E gene, respectively. By comparison with vaacine strains P3 and SA14-14-2, homologies at nucleotide level and deduced amino acid level were 84.1%-85.8% and 93.7%-96.2% in PreM gene, and were 87.6%-88.3% and 97%-97.8% in E gene, respectively. The neurovirulence-related 8 amino acid sites encode by E gene remained unchanged in 13 JEV strains.</p><p><b>CONCLUSION</b>JEV with genotype I predominated in Sichuan, nucleotide sequences and deduced amino acid sequences in PreM gene and E gene were highly conserved, key neurovirulence-rerlated sites remained unchanged. It suggested currently used vaccine is still capable of preventing JEV infection.</p>