Human norovirus transmission and evolution in a changing world

Key Points Norovirus infections pose a substantial risk to human health worldwide. Modes of viral transmission, the severity of illness and evolutionary pressures all contribute to this risk and can vary between viral genotypes. Many details about the transmission of noroviruses remain unknown, especially regarding the origin of newly emerging strains. The recent emergence of genotype GII.P17-GII.17 noroviruses in Asia should serve as a warning that future risks from norovirus outbreaks might arise from genotypes other than those currently targeted by vaccine development. Bacteria in the host microbiota might influence human norovirus infections by providing HBGA-like sugars for norovirus attachment and by modulating host immunity. B cells support norovirus replication in the presence of bacteria that express histo-blood group antigen (HBGA)-like sugars. A recently described cell culture system for the study of noroviruses in B cells will hopefully advance our understanding of many aspects of human noroviruses, ranging from the molecular characterization of their life cycle to the development of improved vaccines. In the modern world, several factors have increased the global health challenge posed by noroviruses. In this Review, Koopmans and colleagues describe advances in the study of norovirus transmission, pathogenesis and evolution, and consider future prospects for therapeutics. Norovirus infections are a major cause of gastroenteritis, and outbreaks occur frequently. Several factors are currently increasing the challenge posed by norovirus infections to global health, notably the increasing number of infections in immunocompromised individuals, who are more susceptible to disease, and the globalization of the food industry, which enables large norovirus outbreaks to occur on an international scale. Furthermore, the rapid rate of the genetic and antigenic evolution of circulating noroviruses complicates the development of vaccines and therapies that are required to counter these challenges. In this Review, we describe recent advances in the study of the transmission, pathogenesis and evolution of human noroviruses, and consider the ongoing risk of norovirus outbreaks, together with the future prospects for therapeutics, in a rapidly changing world.