- IBD was first described as a specific new disease by Cosgrove in 1962 in the town of Gumboro, Delaware, USA.
- Variant IBDV strains were first reported in the USA in 1986/87.
- Hyper or very virulent IBDV strains were first reported in Belgium and The Netherlands in 1987.
- Currently IBDV has a worldwide distribution, occurring in all major poultry producing areas.
- The classical and hyper virulent forms of IBD are predominant in all countries with the exception of North America and Australia.
- In the USA the variant strains of IBDV predominate.
Peer Reviewed by Dr J J (Sjaak) de Wit and William Baxendale.