Genomic characterization of echovirus 6 causing aseptic meningitis in Hokkaido, Japan: a novel cluster in the nonstructural protein coding region of human enterovirus B

Molecular epidemiological characteristics of echovirus 6 in mainland China: extensive circulation of genotype F from 2007 to 2018

Echovirus 6 (E6) is associated with various clinical diseases and is frequently detected in environmental sewage. Despite its high prevalence in humans and the environment, little is known about its molecular phylogeography in mainland China. In this study, 114 of 21,539 (0.53%) clinical specimens from hand, foot, and mouth disease (HFMD) cases collected between 2007 and 2018 were positive for E6. The complete VP1 sequences of 87 representative E6 strains, including 24 strains from this study, were used to investigate the evolutionary genetic characteristics and geographical spread of E6 strains. Phylogenetic analysis based on VP1 nucleotide sequence divergence showed that, globally, E6 strains can be grouped into six genotypes, designated A to F. Chinese E6 strains collected between 1988 and 2018 were found to belong to genotypes C, E, and F, with genotype F being predominant from 2007 to 2018. There was no significant difference in the geographical distribution of each genotype. The evolutionary rate of E6 was estimated to be 3.631 × 10^-3 substitutions site^-1 year^-1 (95% highest posterior density [HPD]: 3.2406 × 10^-3-4.031 × 10^-3 substitutions site^-1 year^-1) by Bayesian MCMC analysis. The most recent common ancestor of the E6 genotypes was traced back to 1863, whereas their common ancestor in China was traced back to around 1962. A small genetic shift was detected in the Chinese E6 population size in 2009 according to Bayesian skyline analysis, which indicated that there might have been an epidemic around that year.

Aseptic meningitis outbreak associated with echovirus 4 in Northern Europe in 2013-2014

Picornaviruses (family Picornaviridae) are small, nonenveloped, positive-sense, single-stranded RNA viruses. The members of this family are currently classified into 47 genera and 110 species. Of picornaviruses, entero- and parechoviruses are associated with aseptic meningitis. They are transmitted via fecal-oral and respiratory routes, and occasionally, these viruses may cause a brief viremia and gain access to central nervous system (CNS). During the diagnostic screening of entero- and parechovirus types in Finland in year 2013-14, we detected a cluster of echovirus 4 (E4) infections in young adults and adolescents. As E4 is infrequently detected in Finland, we contacted several Northern and Central European laboratories that conduct routine surveillance for enteroviruses and, for those who have had E4 cases, we send a query for E4 sequences and data. Here we report CNS infections caused by E4 in Finland, Sweden, Norway, Denmark, Iceland and Germany in 2013 and 2014, and show that the E4 detected in these countries form a single lineage. In contrast, E4 strains circulating in these countries preceding the year 2013, and those circulating elsewhere in Europe during 2013-2014, formed several independent clusters.

Genetic characterization of a novel recombinant echovirus 30 strain causing a regional epidemic of aseptic meningitis in Hokkaido, Japan, 2017

A regional epidemic of aseptic meningitis caused by echovirus 30 (E30) occurred in Hokkaido, Japan, during the period of August-December 2017. To investigate their phylogenetic relationship to other human enteroviruses, we determined the complete genomic nucleotide sequences of isolates from this outbreak. Phylogenetic analysis of the viral capsid protein 1 gene showed that the strains were most closely related to E30 strains detected in Germany, France, and Russia in 2013. In contrast, the region encoding the viral protease and the RNA-dependent RNA polymerase had a close phylogenetic relationship to non-E30 enteroviruses detected in the United Kingdom and Switzerland in 2015-2017, suggesting that a recombination event had occurred.

Molecular characterization of environmental and clinical echovirus 6 isolates from Poland, 2006-2014

The aim of this study was to investigate the genetic variability of echovirus 6 (E6) isolates from environmental samples and clinical cases of aseptic meningitis from 2006 to 2014. The analysis of the VP1 region showed the extensive diversity (up to 18.8%) and revealed that E6 circulating in Poland belong to four groups. Environmental strains clustered in three groups excepting the 2012 outbreak group, which shows the sudden introduction of new epidemic variant with Asiatic origin. Data from the study established relationships of E6 from Poland with previously characterized strains and confirmed the importance of both clinical and environmental surveillance. J. Med. Virol. 89:936-940, 2017. © 2016 Wiley Periodicals, Inc.

Complete genome sequence analysis of two human coxsackievirus A9 strains isolated in Yunnan, China, in 2009

Human coxsackievirus A9 (CVA9) is a member of Enterovirus B species and may cause aseptic meningitis. The complete genome analyses of two strains CVA9 A242/YN/CHN/2009 and A108/YN/CHN/2009 isolated from aseptic meningitis cases in Yunnan Province, China, in 2009 were performed. These two strains shared 81.3 and 80.7, 81.0 and 81.1 % nucleotide similarity with prototype strain Griggs in the VP1-encoding sequence and the complete genome sequence, respectively. Through phylogenetic analysis and homogeneity analysis for twenty-eight VP1-encoding sequences, CVA9 strains could be divided into four genotypes and the Chinese strains might belong to genotype D. Similarity plot and bootscanning analyses showed evidence of recombination with other EVB viruses. In conclusion, persistent surveillance of circulating enterovirus might help understand the enterovirus evolution.

Recombination among human non-polio enteroviruses: implications for epidemiology and evolution

Human enteroviruses (EV) belong to the Picornaviridae family and are among the most common viruses infecting humans. They consist of up to 100 immunologically and genetically distinct types: polioviruses, coxsackieviruses A and B, echoviruses, and the more recently characterized 43 EV types. Frequent recombinations and mutations in enteroviruses have been recognized as the main mechanisms for the observed high rate of evolution, thus enabling them to rapidly respond and adapt to new environmental challenges. The first signs of genetic exchanges between enteroviruses came from polioviruses many years ago, and since then recombination has been recognized, along with mutations, as the main cause for reversion of vaccine strains to neurovirulence. More recently, non-polio enteroviruses became the focus of many studies, where recombination was recognized as a frequent event and was correlated with the appearance of new enterovirus lineages and types. The accumulation of multiple inter- and intra-typic recombination events could also explain the series of successive emergences and disappearances of specific enterovirus types that could in turn explain the epidemic profile of circulation of several types. This review focuses on recombination among human non-polio enteroviruses from all four species (EV-A, EV-B, EV-C, and EV-D) and discusses the recombination effects on enterovirus epidemiology and evolution.

Successful control of an echovirus 6 meningitis outbreak in a neonatal intensive care unit in central Greece

We report an outbreak of echovirus 6 meningitis in a neonatal intensive care unit in central Greece from July to August 2011. The most probable source of the outbreak was a mother; during hospitalization, her neonate was initially infected, followed by 7 more. Stricter infection control measures were implemented, and no other cases have been observed.

Recombination and evolutionary dynamics of human echovirus 6

Enterovirus (EV) infections are associated with a wide array of often severe disease presentations including aseptic meningitis, encephalitis, and acute flaccid paralysis. Surveillance for polioviruses and other EVs is therefore important as a public health measure both for patient management and epidemiological studies. From 1988 to 2008, echovirus (E) 30 was the predominant genotype in Spain (33.7% of the total typed EVs). E6 was also endemic throughout this period although isolated less frequently (12.5%). In 2009, however, a substantial increase in the incidence of E6 was detected (60%), displacing E30 type (2%). To investigate the evolution and recombination in the epidemiology and transmission of E6 in Spain, a genetic analysis in VP1 and 3Dpol regions of 67 Spanish strains collected during the period 2004-2010 was performed. All VP1 sequences clustered monophyletically in the assigned genogroup C, subgroup 9, currently the predominant circulating strains identified in Europe and elsewhere in the last 10 years. 3Dpol sequences were interspersed with other species B EVs resulting from several recombination events that generated at least 12 different recombinant forms (RFs) among study samples. These showed typically minimal divergence in VP1. The co-circulation of different lineages of E6 in the same geographical area associated with its mainly endemic pattern of transmission may have contributed to the extremely short estimated half-life of E6 RFs (0.87 years). This pattern contrasts markedly with other species B EVs and EV71 where VP1 lineage expansion and extinction occurred in step with defined recombination events and periodic changes in incidence.