The major drawback of currently available databases of homologous families to the study of viral homologies and lateral gene transfer in viruses is their taxonomic compartimentalization. Indeed, current databases present families of homologies either restricted to viruses only [Protein Clusters (8) , GeneTree (9) ] or to viral taxonomic groups [Viral Orthologous Cluster (10) ], some also not presenting viral information [HomoloGene (11) ]. The few databases that do present viral and non-viral sequences, such as Pfam (12) or the Conserved Domain Database (13) do not provide complete phylogenetic trees. This translates into the fact that it is not currently possible to have a global view on viral-host lateral gene transfers due to the difficulty of obtaining global information on cross-taxa transfers at the viral level.