Caliciviruses, once thought to infect only swine, were considered eradicated from domestic herds in 1959. Later it was discovered that related caliciviruses could be found in profuse variety amongst the creatures of the sea. Remarkably, the host spectrum of caliciviruses, which once seemed so restricted, was found to be unusually diverse and capable of bridging wide phylogenehc distances. T h s vital characteristic appears now to be aiding these unusual and highly adaptive viruses in crossing not only species lines but also the land-sea interface, and they apparently are again becoming established as important disease agents of land animals. The geographical distnbution, host spectra, pathogenic potential, and possible public health significance of these vlruses, are the subject of this review.

Neutral17ing antibodies to San M~g u e l sea llon virus (SMSV) types 6 and/or 7 were found in sera collected from California sea l~o n s Zalophus c californianus in 1977 and 1983 and in sera collected from Steller sea lions Eumetoplas jubatus in 1976 and 1985 The combined prevalence rates of ShlSV anubodies in these 2 species were SMSV-6 19/228 = 8.3 %, and SMSV-7, 4/228 = 1 7 '10 Titers ranged from 1 20 to 1 320 by standard microtlter neutralization assay Seropositive sea lions were dispersed along the eastern Pacific rim from Alaska to the southern California Channel Islands Anhbodies to either agent were not found In sera collected from northern fur seals Callorhlnus urslnus, Pacific walruses Odobenus rosnlarus divergens seals of the family Phocidae, or several cetacean species Both SMSV-6 and SMSV-7 have been isolated from opaleye G~rella nlgrIcans an ocean fish found pnmarily In the southern California coastal zone, the presence of antibody-positive sea llons in more northern waters indicates that these piscine-ongin SMSV types may have a wider distribution in nature than has been previously supposed