First characterization of a Middle-East GI-23 lineage (Var2-like) of infectious bronchitis virus in Europe

•Infectious bronchitis virus (IBV) of GI-23 lineage was prevalent for nearly 20 years only in countries of the Middle East.•This is the first detection and genetic characterization of the GI-23 IBV in Poland.•Complete sequence of Polish GI-23 IBV was phylogenetically distinct from all of the full-length genome sequences analyzed.•Recombination events within 1a, 1b, N genes were identified. Variants assigned to GI-23 lineage of infectious bronchitis virus (IBV), formerly called Var2, have circulated for nearly 20 years only in countries of the Middle East. Strains of this lineage were first identified in Israel in 1998. More severe form of the virus appeared in 2006, when the second wave of Var2 epidemic has spread over the Middle East region. The present study describes the detection and detailed genetic characterization of the GI-23 viruses in Poland. The full-length genome of gammaCoV/Ck/Poland/G052/2016 strain consists of 27596 nucleotides and has typical organization for IBV (UTR5′-POl-S-3a-3b-E-M-4b-4c-5a-5b-N-UTR3′). The phylogenetic analysis of the complete sequence showed that it formed separate branch distinct from all of the full-length genome sequences analyzed in this study. Recombination analyses with other gammacoronaviruses revealed that Polish GI-23 strain may originate from recombination events and potential donors of build-in sequences are IBV of GI-1, GI-13 and G-19 lineages (Mass-, 793B- and QX-like strains, respectively). The 1a, 1b and N genes were involved in these recombination events. The source of virus introduction to the chicken population in Poland is unknown.