Continuous evolution of avian infectious bronchitis virus resulting in different variants co-circulating in Southern China.

Sixty field strains of avian infectious bronchitis virus (IBV) were isolated from chicken flocks in different regions of Guangxi from 1985 to 2012. Phylogenetic analysis of S1 subunit glycoprotein genes revealed that field isolates from 2009-2011 mostly belonged to the LX4 type, while those from 1985-2008 belonged to the HN08 type, and a few others belonged to the 4/91 type, the TW type and the Mass type. In addition, it is noteworthy that no obvious regional differences were found among these 60 strains isolated from six regions in Guangxi, while there was a high degree of sequence identity among the isolates in the same period of time.