Orthonairovirus is a genus in the family Nairoviridae of the order Bunyavirales that include viruses with circular, negative-sense single stranded RNA. It got its name from the Nairobi sheep disease that affects the gastrointestinal tracts of sheep and goats. The vast majority, and perhaps all viruses in this genus are tick-borne viruses that can have human or other vertebrate hosts. Orthonairovirus is a genus in the family Nairoviridae of the order Bunyavirales that include viruses with circular, negative-sense single stranded RNA. It got its name from the Nairobi sheep disease that affects the gastrointestinal tracts of sheep and goats. The vast majority, and perhaps all viruses in this genus are tick-borne viruses that can have human or other vertebrate hosts. Nairobi sheep disease orthonairovirus (NSD) is the prototype virus of the genus. NSD is found in East and Central Africa, and causes acute hemorrhagic gastroenteritis in sheep and goats. The genus is divided into at least nine serogroups. The Hughes and Sakhalin serogroups appear to be sister groups.