Prior to 1972, caliciviruses were known to naturally infect only swine (vesicular exanthema of swine virus) and cats (feline calicivirus). Since 1972 eight different calicivirus antigenic types have been isolated from three species of pinnipeds and one species of teleost. The different serotypes lack host specificity among the marine animals tested and the four serotypes tested in swine readily cause clinical vesicular exanthema.  Serum surveys have shown that five terrestrial mammal species tested including man have developed specific serum neutralizing antibodies to caliciviruses of marine origin.