Abstract: Murine Norovirus l(MNV-l) is a newly recognized pathogen of mice that causes lethal infection in mice deficient in components of the innate immune response. Moreover, the murine virus 1 is the only norovirus that can replicate in cell culture and in a small animal. Murine norovirus 1 is detected by virus isolation, immunohistochemistry method and RT-PCR technique.