picornavirus One of a group of small RNA-containing viruses (pico = small; hence pico-RNA-virus) commonly present in the alimentary and respiratory tracts of vertebrates. They cause mild infections of these tracts but the group also includes the polioviruses, which attack the central nervous system causing poliomyelitis; and the causal agent of foot and mouth disease in cattle, sheep, and pigs.

picornavirus (pi-kor-nă-vy-rŭs) n. one of a group of small RNA-containing viruses. The group includes Coxsackie viruses, polioviruses, and rhinoviruses.