The Orthomyxoviridae ( orthos , Greek for `` straight '' ; myxa , Greek for `` mucus '' ) are a family of RNA viruses . They include five genera : Influenzavirus A , Influenzavirus B , Influenzavirus C , Thogotovirus and Isavirus . The Orthomyxoviridae ( orthos , Greek for `` straight '' ; myxa , Greek for `` mucus '' ) are a family of RNA viruses that includes five genera : Influenzavirus A , Influenzavirus B , Influenzavirus C , Isavirus and Thogotovirus .