What is "avibirnavirus"

Avibirnavirus is a genus of viruses, in the family Birnaviridae. Young chickens and other fowl serve as natural hosts. There are currently only one species in this genus: the type species Infectious bursal disease virus. Diseases associated with this genus include: IBDV causes severe inflammation of the bursa of fabricius. The disease causes considerable morbidity and mortality in an acute form or as a consequence of severe immunosuppression provoked by the destruction of immature B-lymphocytes within the bursa of fabricius.