In the past, arboviruses were organized into one of four groups: A, B, C, and D. Group A denoted members of the genus Alphavirus,[39][40] Group B were members of the genus Flavivirus,[41] and Group C remains as the Group C serogroup of the genus Orthobunyavirus.[42] Group D was renamed in the mid-1950s to the Guama group and is currently the Guama serogroup in the genus Orthobunyavirus.[43] This renaming of the group was because the number of groups would eventually exceed the length of the alphabet. Since then, the organization of arboviruses into these groups has fallen out of usage as the standard biological classification system has become more preferred for classifying viruses.[43] With the exception of the African swine fever virus, which belongs to the Asfarviridae family of viruses, all major clinically important arboviruses belong to one of the following four families: