Influenza viruses are highly variable RNA viruses that can affect birds and mammals including humans. There are currently three species of these viruses, designated influenza A, B and C. A new influenza C-related virus recently detected in livestock has been proposed as “influenza D.”
Iowa State University
Spickler, Anna Rovid, "Influenza" (2016). Center for Food Security and Public Health Technical Factsheets. 76.