The Earth's oceans are the primary reservoir for an emerging family of RNA viruses, the Caliciviridae, which can cause a spectrum of diseases in marine animals, wildlife, farm animals, pets and humans. Certain members of this family have unusually broad host ranges, and some are zoonotic (transmissible from animals to humans). The RNA virus replicative processes lack effective genetic repair mechanisms, and, therefore, virtually every calicivirus replicate is a mutant. Hence, traditional therapeutics dependent on specific nucleic acid sequences or protein epitopes lack the required diversity of sequence or conformational specificity that would be required to reliably detect, prevent or treat infections from these mutant clusters (quasi-species) of RNA viruses, including the Caliciviridae. Antisense technology using phosphorodiamidate morpholino oligomers shows promise in overcoming these current diagnostic and therapeutic problems inherent with newly emerging viral diseases.