Avian orthoreovirus infection is more common in young birds, because resistance begins to develop from as young as two weeks of age. It is also reportedly more common in broilers. Distribution of avian orthoreovirus is worldwide and it is present in most poutry flocks. It can be transmitted horizontally via the faeces or rarely, vertically. It is not a zoonosis.
The most common symptom is lameness. There may also be swelling or bleeding around the joints. Gastrointestinal, respiratory and neurological signs have also been reported.