Comparative analysis of four Massachusetts type infectious bronchitis coronavirus genomes reveals a novel Massachusetts type strain and evidence of natural recombination in the genome

- Massachusetts-type is the most prevalent serotype of infectious bronchitis virus worldwide.
- Analysis of genomic sequences provides more information about occurrence, origin and evolution.
- Pathogenic, non-pathogenic and recombinant Mass-type IBVs are co-existing in chicken flocks in China.
- Data of Mass-type from isolates in China can help to explain the emergence of Mass-type IBV.