An outbreak of Japanese encephalitis caused by genotype Ib Japanese encephalitis virus in China, 2018: A laboratory and field investigation

摘要

Japanese encephalitis virus (JEV) is recognized as an important encephalitis pathogen all over the world. Its genotype is divided into GI-V. In recent years, JEV GIb (a temperate genotype) has gradually replaced GIII as the prevalent strain in JE endemic areas. Although JEV GIb originated from tropical Asia along with JEV GIa, it has rapidly spread for its advantages in wintering and infecting vectors. Although there have been epidemics caused by JEV GI and GIII, there have been no reports of a JE outbreak caused by JEV GIb alone in northeastern Asia. However, a JE outbreak occurred in the Ningxia Hui Autonomous Region in northern China in summer 2018 which was the first outbreak in Ningxia in recent decades. This paper presents a series of laboratory and field studies of this outbreak. The strain isolated from JE cases as well as JEV detected in Culex tritaeniorhynchus collected from local areas in nature all belonged to JEV GIb and were in the same evolutionary clade. This is the first report of a JE outbreak caused by JEV GIb infection in northeastern Asia (latitude 35 14' 39 23' N, longitude 104 17' 107 39' E), which used to be a low endemic area of JEV GIII.