Objective  Epidemiology and genetic variations of the infectious bronchitis virus (IBV) in Fujian province were studied.

  Method   Two strains of virus isolated from the diseased chickens in Fujian in 2021 were identified by chicken embryo pathogenicity test, electron microscope observation, and RT-PCR. S1 genes of the isolates were cloned, sequenced, and analyzed using biological software.

  Result  The two IBV strains were code named FJ-NP01 and FJ-FZ01. The full length of S1 of FJ-NP01 was 1629 nt encoding 543 amino acids, and that of FJ-FZ01, 1620 nt encoding 540 amino acids. The S1 gene cleavage site of FJ-FZ01 was HRRRR, same as all reference strains of genotype I branch; while that of FJ-NP01 HRRKR differed from the reported site of IBV isolated from genotype Ⅳ but same as that of TC07-2 reference strain of genotype Ⅵ. The homology of nucleotide and amino acid between the two isolates was 83.2% and 79.6%, respectively, but merely 75.7%–76.3% and 77.1%–83.5% with the Mass-type conventional vaccines H120 and H52, respectively. Further analysis showed that FJ-NP01 was from a recombination event between CK CH GD LZ12-4 and L-1148, the homology of nucleotide acid between 1438–1506 nt of FJ-NP01 with CK CH GD LZ12-4 was 97%, and 95.9% between the other nucleotide acid of S1 gene with L-1148 .

  Conclusion   It appeared that the IBV epidemic experienced in the province was complex in nature and that the existing Mass vaccines would not provide sufficient immune protection to deter the spread.