Analysis of coxsackievirus A6 circulation in the territories of the Far Eastern Federal district of the Russian Federation in 2014–2019

Introduction. Molecular epidemiological monitoring of enterovirus infection (EVI) in the territories of the Russian Federation showed that coxsackievirus A6 (CVA-6) had been one of the most prevalent types of enteroviruses that circulated among the country population during last years and had caused majority of EVI outbreaks. Objective — to evaluate coxsackievirus A6 circulation in the territories of the Far Eastern Federal district (FEFD) in 2014–2019 utilizing methods of molecular genetics. Materials and methods. RT-PCR was employed to detect enterovirus RNA in biological material collected in 9 territories of the FEFD . In order to establish enterovirus types, amplification of positive samples was carried out to detect nucleotide sequence fragments of the VP1 and VP2 genes. Molecular genetic analysis of the Far Eastern CVA-6 strains was based on detection of nucleotide sequences of VP1 and 3Dpol gene fragments. Phylogenetic trees were constructed by the means of Bayesian phylogenetic methods. Results. Total 1773 nucleotide sequences of 43 types of non-polio enteroviruses were obtained in 2014-2019. Majority of the sequences belonged to coxsackievirus A6 (524; 29.5%). In the years of the highest CVA-6 detection an increase in EVI incidence as well as EVI outbreaks were observed in the territories of FEFD. The most prevalent manifestations of EVI caused by CVA-6 in FEFD were herpangina and exanthemic forms. Phylogenetic analysis showed that Far Eastern strains of CVA-6 during in the analyzed period of time belonged to D3 subgenotype that is dominant in the world. The circulation of several recombinant forms of CVA-6 (RF-A, -H, -L, -N, -R) was also registered. Conclusion. The genetic diversity of CVA-6 strains circulating in the territories of the FEFD in 2014–2019 revealed in this study requires further investigation in order to obtain new knowledge about the CVA-6 molecular epidemiology and improve the enterovirus surveillance system.