Caliciviruses were once thought to naturally infect only swine. Subsequently, those agents were eradicated from domestic swine and believed to then be extinct. Somewhat later it was discovered that an abundance of caliciviruses were to be found in profuse variety amongst the animals of the sea. More remarkable, their host specificity which had been thought to be so very restrictive was, in fact, unusually broad, crossing wide phylogenetic distances. This characteristic now appears to carry these unusual and highly adaptive viruses across not only species lines but also across the land-sea interface where they are apparently becoming established as infectious agents among land animals. The geographic distribution, the host spectrums, the disease potential and, finally, the possible public health significance of these agents will be discussed.