Sequence comparison of the GP and NP genes from the New World arenaviruses revealed three distinct clade, A, B and C. In addition, the North American arenaviruses, that include WWAV, are most closely related to clade A in the NP gene, but clade B in GP. A/B Rec. refers to this putative recombinant lineage. The strains that are pathogenic for humans (*) are found throughout clade B, in each of the three distinct sub-groups, B1, B2 and B3. The pathogenicity of WWAV remains unclear. Adapted from Charrel et al., 2001, 2002)