Department of Internal Medicine, Fujita Health University Nakakuri Sanatorium, Mie 514-1295, Japan.
Infect Genet Evol. 2012 Oct;12(7):1524-34. doi: 10.1016/j.meegid.2012.06.002. Epub 2012 Jun 15.
In Mie prefecture in Japan, 12 cases of sporadic hepatitis E occurred from 2004 to 2011. Mie prefecture is located in the central region of Japan, far from the most prevalent regions of hepatitis E virus (HEV) infection in Japan, the north and northeastern part. These 12 cases did not have any common risk factors of HEV infection. We analyzed the molecular epidemiology of the cases in Mie prefecture. We obtained the nucleotide sequences of the HEV strains and analyzed them with the sequences of other HEV strains by phylogenetic and coalescent analyses. Japan-indigenous genotype 3 HEV strains were divided into two major subtypes, namely, 3a and 3b; one minor subtype, 3e; and a few other unassigned lineages. The Japan-indigenous subtype 3e strains were closely related to European subtype 3e HEV strains and were comparatively rare in Japan; however, eight strains of the 12 cases we examined belonged to subtype 3e, indicating a close phylogenetic relationship, despite the lack of common risk factors. Coalescent analyses indicated that the Mie 3e strains seemed to have intruded into Mie prefecture about 10 years ago. Sporadic acute hepatitis E cases caused by the 3e strains occurred consistently from 2004 to 2011 in Mie prefecture. This is the first report of unexpected persistent occurrence of hepatitis by the European-type genotype 3 HEV, subtype 3e, in a country outside of Europe. Phylogenetic and coalescent analyses traced the history of the indigenization of the Mie 3e strains from Europe. Because hepatitis E cases caused by 3e strains are relatively rare in Japan, molecular evolutionary analyses of HEV infection in Mie prefecture is important for preventing a future hepatitis endemic or epidemic by 3e strains in Japan.
在日本三重县，2004 年至 2011 年期间发生了 12 例散发性戊型肝炎病例。三重县位于日本中部，远离日本北部和东北部最常见的戊型肝炎病毒（HEV）感染地区。这 12 例病例没有任何共同的 HEV 感染危险因素。我们分析了三重县病例的分子流行病学。我们获得了 HEV 株的核苷酸序列，并通过系统发育和合并分析对这些序列与其他 HEV 株的序列进行了分析。日本本土基因型 3 HEV 株分为两个主要亚型，即 3a 和 3b；一个次要亚型，3e；以及一些其他未分配的谱系。日本本土 3e 亚型株与欧洲 3e 型 HEV 株密切相关，在日本比较罕见；然而，我们检查的 12 例中有 8 例属于 3e 亚型，表明尽管没有共同的危险因素，但存在密切的系统发育关系。合并分析表明，三重 3e 株似乎在大约 10 年前就已经侵入了三重县。2004 年至 2011 年间，三重县持续发生由 3e 株引起的散发性急性戊型肝炎病例。这是首例在欧洲以外的国家报告由欧洲型基因型 3 HEV、3e 型引起的意外持续性肝炎病例。系统发育和合并分析追踪了 Mie 3e 株从欧洲本土化的历史。由于日本 3e 株引起的戊型肝炎病例相对较少，因此对 Mie 县 HEV 感染进行分子进化分析对于防止未来日本 3e 株引起的肝炎流行或流行非常重要。
