A picornavirus is a virus belonging to the
family Picornaviridae. Picornaviruses are non-enveloped, positive-stranded
RNA viruses with an icosahedral capsid. The genome RNA is unusual because it
has a protein on the 5' end that is used as a primer for transcription by
RNA polymerase. The name is derived from pico, meaning small, and RNA,
referring to the ribonucleic acid genome, so "pico-rna-virus" literally
means small RNA virus.
Picornaviruses are separated into a number of genera and include many
important pathogens of humans and animals. The diseases they cause are
varied, ranging from acute "common-cold"-like illnesses, to polio, to
chronic livestock infections. Additional species not belonging to any of the
recognised genera continue to be described
Picornaviruses are separated into a number of genera. Contained within the
picornavirus family are many organisms of importance as vertebrate and human
pathogens, shown in the table below.
Enteroviruses infect the enteric tract, which is reflected in their name. On
the other hand, rhinoviruses infect primarily the nose and the throat.
Enteroviruses replicate at 37°C, whereas rhinoviruses grow better at 33°C,
as this is the lower temperature of the nose. Enteroviruses are stable under
acid conditions and thus they are able to survive exposure to gastric acid.
In contrast, rhinoviruses are acid-labile (inactivated or destroyed by low
pH conditions) and that is the reason why rhinovirus infections are
restricted to the nose and throat.