22Human noroviruses are the leading cause of severe childhood diarrhea worldwide yet we know 23 very little about their pathogenic mechanisms. Murine noroviruses cause diarrhea in interferon-24 deficient adult mice but these hosts also develop systemic pathology and lethality, reducing 25 confidence in the translatability of findings to human norovirus disease. Herein we report that a 26 murine norovirus causes self-resolving diarrhea in the absence of systemic disease in wild-type 27 neonatal mice, thus mirroring the key features of human norovirus disease and representing a 28 robust norovirus small animal disease model. Intriguingly, lymphocytes are critical for controlling 29 acute norovirus replication while simultaneously contributing to disease severity, likely reflecting 30 their dual role as targets of viral infection and key components of the host response. 31 32 MAIN TEXT 33Human noroviruses are the leading cause of severe childhood diarrhea and gastroenteritis 34 outbreaks worldwide 1-3 yet we know very little about their pathogenic mechanisms. While human 35 noroviruses cause modest diarrhea in gnotobiotic piglets, gnotobiotic calves, and miniature 36 piglets 4-6 , a limiting factor in studying norovirus pathogenesis is the lack of tractable small animal 37 models that recapitulate key features of disease observed in infected individuals. The first murine 38 norovirus, MNV-1, was discovered nearly two decades ago 7 and many other MNV strains have 39 been reported since then. MNV strains segregate into two phenotypic categories which differ in 40 many aspects of pathogenesis, including their rate of clearance from infected hosts and cell 41 tropism. MNV-1 is the prototype acute strain. It infects immune cells in the gut-associated 42 lymphoid tissue (GALT) and reaches peak intestinal titers 1-2 days post-infection (dpi) with 43 clearance from the host by 7-14 dpi 8 . MNV-3 and MNV-CR6 are commonly referred to as