BackgroundSeveral studies have shown that the predominant genotype of Chinese Japanese encephalitis virus (JEV) is evolving from genotype 3 to genotype 1. However, in recent years, almost all genotype 1 isolates were from mosquitoes, and genotype 1 has been less associated with human disease than genotype 3. This study reports the isolation of human genotype 1 JEV and its genetic characteristics to provide additional insights into human JE pathogens that are currently circulating in China.Methods and ResultsIn 2009, 31 cerebrospinal fluid samples were collected from patients living in Yunnan and Shanxi provinces and were used to inoculate Aedes albopictus C6/36 cells for virus isolation. The JEV strains were identified using immunofluorescent assays and the reverse transcription-polymerase chain reaction. Phylogenetic analyses based on the partial capsid/pre-membrane and full envelope (E) sequences were performed using Clustalx 1.8 software. Three JEV isolates were obtained from a 4-year-old girl and a 2-year-old boy living in Yunnan and an 82-year-old woman in Shanxi. The boy had been immunized with one dose of JE live attenuated vaccine. New isolates were grouped into genotype 1. Amino acid sequence for the viral E protein indicated 95% to 100% identity with each other and with other JEV strains. When compared with a consensus sequence of E protein, two amino acid substitutions were found: SerE-123-Asn in the two Yunnan isolates and LysE-166-Arg in the Shanxi isolate.ConclusionsOur findings indicate that the genotype 1 of JEV is causing human infections in China. Our observation of a previously vaccinated boy developing JE from genotype 1 virus infection also calls for more detailed studies, both in vitro and in vivo neutralization tests as well as active surveillance, to examine the possibility of a lack of complete protection conferred by the live attenuated JE vaccine against genotype 1 virus.
We isolated 17 viral strains capable of causing cytopathic effects in mammalian cells and death in neonatal mice from sand flies in China. Phylogenetic analysis showed that these strains belonged to the genus Phlebovirus . These findings highlight the need to control this potentially emerging virus to help safeguard public health.
BackgroundThe increasing trend of adult cases of Japanese encephalitis (JE) in China, particularly in northern China, has become an important public health issue. We conducted an epidemiological investigation in the south of Shanxi Province to examine the relationships between mosquitoes, Japanese encephalitis virus (JEV), and adult JE cases.MethodsMosquito specimens were collected from the courtyards of farmers’ households and pig farms in Shanxi Province. Mosquitoes were pooled, homogenized, and centrifuged. Reverse transcription-polymerase chain reaction (RT-PCR) was used to detect mosquito-borne arbovirus genes in homogenates. Specimens positive for these genes were inoculated into the baby hamster kidney cell line (BHK-21) to isolate virus. Minimum infection rate was calculated and phylogenetic analyses were performed.ResultsA total of 7 943 mosquitoes belonging to six species in four genera were collected; Culex tritaeniorhynchus accounted for 73.08% (5 805/7 943), C. pipiens pallens for 24.75% (1 966/7 943), and the remaining 3% (104/ 7943) consisted of Anopheles sinensis, Aedes vexans, Ae. dorsalis, and Armigeres subalbatus. Sixteen pools were positive for JEV based on RT-PCR using JEV pre-membrane gene nested primers. Phylogenetic analyses showed that all JEVs belonged to genotype I; two pools were positive using Getah Virus (GETV) gene primers. In addition, one JEV strain (SXYC1523) was isolated from C. pipiens pallens specimens. These results indicate that the minimum infection rate of JEV in mosquito specimens collected from the courtyards of farmers’ households with pigsties was 7.39/1 000; the rate for pig farms was 2.68/1 000; and the rate for farmers’ courtyards without pigsties was zero.ConclusionsThe high-prevalence regions of adult JE investigated in this study are still the natural epidemic focus of JEV. Having pigsties near dwellings is a potential risk factor contributing to the prevalence of adult JE. To prevent the occurrence of local adult JE cases, a recommendation was raised that, besides continuing to implement the Expanded Program on Immunization for children, the government should urge local farmers to cease raising pigs in their own courtyards to reduce the probability of infection with JEV.Electronic supplementary materialThe online version of this article (doi:10.1186/s40249-017-0312-4) contains supplementary material, which is available to authorized users.
BackgroundJapanese encephalitis (JE) vaccination is the most effective measure for preventing JE disease. The live attenuated JE vaccine, which has shown good efficacy and safety, has been widely used in China.Case presentationsWe report four laboratory-confirmed JE cases detected in JE-endemic areas during the JE virus (JEV) transmission season, who all received a first dose of live attenuated JE vaccine within 2 weeks prior to the onset of illness. All cases presented with acute encephalitis and rapidly reduced consciousness. All cerebrospinal fluid (CSF) samples from the patients were positive for JEV-specific immunoglobulin M (IgM) antibodies, but viral isolation and polymerase chain reaction (PCR) detection of JEV were both negative.ConclusionsIt is difficult to identify a causal link between the disease and the vaccination, as the source of positive CSF JEV IgM antibodies might be natural JEV infection or possibly due to a traumatic lumbar puncture. Our observations highlight the need for public health officers and doctors to consider reasonable vaccination policies during the JE season. In addition, continued surveillance as well as thorough investigation of any events that occur after JE vaccination is necessary.
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