Molecular characterization of echovirus 30 isolates from Poland, 1995-2015.

Echovirus 30 (E30) is one of the most frequently identified enterovirus and a major cause of meningitis in children and adults. To investigate the genetic variability and relationship of E30 isolated from specimens of aseptic meningitis cases that occurred in Poland over a period of 20 years, sequences of VP1 gene were determined and genetic analysis was performed. From 1995 to 2015, 124 E30 were isolated using RD cells, and 58 isolates were sequenced and characterized by phylogenetic analysis of partial VP1 region (793 nt). In general, nucleotide sequence divergence in pairwise comparisons among Polish E30 isolates ranged from 0.0 to 15.0 %. The phylogenetic analysis revealed that E30 circulating in Poland since 1995 belong to two unique groups: Group I, characterized by high divergence (up to 13.1 %), segregated in four subgroups, and showed strong temporal circulation of E30. Group II, detected in Poland in 2013-2014, was closely correlated with two meningitis outbreaks and formed a separate genetically homogeneous group. Phylogenetic analysis revealed that strains from Poland had the closest genetic relationship with not only the isolates previously identified in Europe (Belarus, France, Germany, Italy, Russia) but also those in other parts of the world (Australia, China). Sequences of outbreak isolates were grouped in group II together with those from Russia and China isolated during 2010-2013. The identification of five distinct viral lineages during 1995-2015 confirmed the high E30 genetic diversity which may be an essential precondition for the emergence of new strains responsible for further potential aseptic meningitis outbreaks.