The Ljungan virus is part of the Picornaviridae family. Various members of this family cause a variety of separate illnesses among both animals and humans. These illnesses range from asymptomatic infections, common colds and conjunctivitis to severe hepatitis, meningitis and paralysis. Poliovirus, which causes polio, is perhaps the best known member of the family.
Picornaviruses are small – “pico” means small. The virus particles are only 18-30 nm in diameter. The virus has a single stranded RNA genome of about 7000 base pairs. Compared to other viruses this is a relatively small genome.