oss protection among closely related serotypes [9]. In China, IBV was first observed during the early 1980s, and outbreaks have since been frequently reported [7]. The QX-like genotype is thought to have originated during the mid-1990s and continues to be the predominant strain, whereas the LDT3, 4/91, and Taiwan subtypes have also recently been frequently isolated in China [10], [11], [12], [13]. Severe nephritis, false layer syndro