Genetic evolution and vaccine challenges in norovirus genogroup II infection

Norovirus genogroup II (GII) is the most common etiology of acute gastroenteritis on a global level, and this is due to a significant degree of genetic heterogeneity, rapid adaptive evolution, and extremely efficient person-to-person and environmental transmission systems. Within GII, rapidly evolving lineages such as GII.4 and episodically emerging genotypes like GII.17 (driven by capsid antigenic drift and novel open reading frame 1/open reading frame 2 (ORF1/ORF2) recombinants) exhibit frequent adaptation and multi-continent expansion. Genotypes including GII.2, GII.3, and GII.6 remain relatively stable over decades yet continue to account for a substantial proportion of disease. This review combines current evidence on the evolutionary dynamics of norovirus GII, which defines the patterns of genotype replacement, the recombination mechanisms between ORF1 and ORF2, and the structural factors of antigenic variability that contribute to immune evasion and determine the epidemiology in the world. We also review advances in diagnostics, including reverse transcription quantitative PCR (RT-qPCR), digital PCR, new isothermal amplification, biosensor platforms, and wastewater surveillance, which are collectively sensitive and more accurate in quantification, and in real-time monitoring in the clinical, food safety, and environmental fields. We also discuss the modern situation in vaccine development, including the use of virus-like particle preparations, messenger RNA (mRNA)-based strategies, and oral adenoviral vectors, their antigenic compositions, key clinical milestones, and the ongoing challenges of lack of robust correlates of protection and overall cross-genotype protection. Key gaps remain in understanding, requiring focused research and policy efforts to improve vaccines and control strategies.