Wesselsbron disease is caused by Wesselsbron virus, an arthropod-borne virus in the genus Flavivirus of the family Flaviviridae. This virus has the properties typically found in a hemagglutinating flavivirus, but is not yet well-characterized.
Iowa State University
Iowa State University Center for Food Security and Public Health, "Wesselsbron Disease" (2007). Center for Food Security and Public Health Technical Factsheets. 145.