 These findings suggest that RNA-RNA recombination may play a significant role in the natural evolution and neuropathogenesis of coronaviruses.The mechanism of recombination appears to involve template switching during viral genome replication, a process referred to as copy choice recombination.Sialodacryoadenitis virus (SDAV), which is a strain Rat coronavirus, is highly infectious coronavirus of laboratory rats, which can be transmitted between individuals by direct contact and indirectly by aerosol.