Orbivirus is a genus of double-stranded RNA viruses in the family Reoviridae and subfamily Sedoreovirinae.

Orbiviruses are named after their characteristic doughnut-shaped capsomers (orbis in Latin means ring).

Many orbiviruses are transmitted by ticks or haematophagus insect vectors (Culicoides, mosquitoes and sand flies) and have a wide host range that includes cattle, goats and sheep, wild ruminants, equids, camelids, marsupials, sloths, bats, birds, large canine and feline carnivores, and humans.

[1][2] In 1719, African horse sickness virus (AHSV) caused the first major recorded orbivirus epidemic, killing 1,500 animals.

VP1, VP4, and VP6 are minor enzymatic proteins that are packaged along with the 10 genome segments within the central space of the virus core.

The orbivirus outer-capsid layer is composed of two additional structural proteins (VP2 and VP5) which mediate cell-attachment and penetration during initiation of infection.

It forms tubules that may be involved in translocation of progeny virus particles to the cell membrane.

NS2 is phosphorylated by cellular kinases and is an important matrix protein of the granular viral inclusion bodies that form within the cytoplasm of infected cells.

During the budding process, they transiently acquire a lipid envelope which can be detected for a short period of time following their release, but this is subsequently lost.

Orbiviruses are vector-borne pathogens transmitted between vertebrate hosts by vectors such as mosquitoes, midges, gnats, sandflies, and ticks.

[5][6] Other species of orbiviruses are responsible for other diseases of animals such as African horse sickness and equine encephalosis virus.