Etiology
IBV was the first coronavirus described and varies greatly genetically and phenotypically, with hundreads of serotypes and strains described. Coronaviruses contain the largest known viral RNA genome in number of nucleotides, of approximately 30,000 bases. The RNA forms a single strand and single segment. IBV diversity is based on transcriptional error, which may become very relevant if occurring in genomic sequences coding for proteins, involved in adsorption to target cell or inducing immune responses. Transcriptional error variants may emerge with evolutional advantage in susceptible chickens. Large genomic changes will occur with entire gene interchanges, by reassortment, as for its replication, seven subgenomic mRNAs are produced and will enable reassortment in coinfections.
Read more about this topic: Avian Infectious Bronchitis