The livers of rZH501-M847-A-infected mice showed multifocal hepatocellular necrosis with prominent aggregating mononuclear inflammatory cells and sparsely scattered viral antigens throughout the liver lobe as early as day 2 p.i. On day 3 p.i., most of the hepatocytes were necrotic and positive for viral antigens (Fig. 6B) . Also, severe hemorrhages were noted throughout the lobe. After day 4 p.i., the livers from mice examined showed less severe hepatocellular damage than livers taken earlier, and the livers examined on day 6 p.i. showed near complete resolution. ZH501infected mice presented with similar lesions and distribution of viral antigens, and yet the progress of the lesions was somewhat slower than those in rZH501-M847-A-infected mice (Fig. 6A) . Although rZH501-M847-G-infected mice had focal-to-multifocal hepatocellular necrosis from days 2 to 4 p.i (Fig. 6C) , they exhibited mild hepatic lesions compared to ZH501-infected mice and rZH501-M847-A-infected mice. Among mice inoculated with the mixture of rZH501-M847-G and rZH501-M847-A, one showed severe hepatic lesions like those of rZH501-M847-Ainfected mice, while others had mild hepatic lesions like that of rZH501-M847-G-infected mice (data not shown).