Reassortment in infectious bursal disease virus (IBDV) and related birnaviruses

The Birnaviridae family consists of non-enveloped viruses with a single capsid that have a double-stranded RNA genome divided into two segments. Because they infect birds, fish, rotifers, marine mollusks, and insects, these viruses are of major economic significance to the global poultry and aquaculture industries. In the last decade, reassortment events have led to the emergence and spread of new strains of infectious bursal disease virus (IBDV) in poultry that could complicate control efforts. This review summarizes the literature regarding the molecular epidemiology and pathogenesis of reassortant birnaviruses, discusses potential reservoirs of gene segments, and highlights gaps in our knowledge of the molecular basis underpinning the phenomenon.