Abstract
Recent research on faba bean necrotic stunt virus, aiming to understand how multipartite viruses function and potentially their existence, revealed three surprising features: a non-uniform segment frequency distribution (genome formula), a multicellular functioning, and the non-concomitant transmission of genomic segments. We review the occurrence of these features in other multipartite viruses and discuss their potential operation in monopartite viruses with segmented genomes and perhaps even in viruses with nonsegmented genomes.