Human noroviruses are the leading cause of acute gastroenteritis outbreaks worldwide, responsible for >685 million infections annually (1). Still, there are no approved vaccines, antivirals, or specific treatments. One promising approach involves the use of compounds that block norovirus attachment to histo-blood group antigens (HBGAs), which serve as essential co-factors for viral entry (2, 3). Human milk oligosaccharides (HMOs), such as 2′-fucosyllactose (2′-FL), have already demonstrated this capability, where the primary fucose moiety of HMOs bound precisely at the HBGA pocket on the capsid (4–10). Building on this concept, we further investigated the antiviral potential of polysaccharide (fucose-based) fucoidans and ulvan extracted from various seaweed species (Fig. 1), which have shown promising inhibition capacities for noroviruses (11–14) and other viruses (15).