 To further investigate the association between secretor status and susceptibility to Norwalk virus NV, we collaborated with Dr. Christine Moe at Emory Universitys School of Medicine on a volunteer challenge study. This study utilized the prototype NV, the first Norovirus strain to be used for human challenge studies. Saliva samples from 77 NV-challenged volunteers were tested for secretor status and for NV-binding. Fifty-five 71 of the 77 volunteers were secretors. Among the 55 secretors, 34 62 were infected with NV following challenge and saliva from 41 75 bound NV recombinant VLPs. None of the saliva samples from the 22 non-secretor volunteers bound NV virus-like particles VLPs and none of them became infected following NV challenge; strongly suggesting that the susceptibility to NV is determined at least in part by the ability of the host to bind the norovirus strain. 