Original name of the plant virus, Watermelon mosaic virus, was changed as Watermelon mosaic virus 2 (WMV 2) in 1982 (ICTV 4th Report). In 1999 ICTV Executive Committee reinstated the virus name, Water mosaic virus. On the basis of genomic sequence of 3' untranslated region, WMV 2 and Soybean mosaic virus - N strain (SMV-N) could be regarded as strains of one virus (Frenkel, MJ, et al., 1989). A virus isolated from Vanilla fragrans was assigned as a strain of Watermelon mosaic virus 2 based on 2006 ICTV Universal Virus Database. Do not confuse with Watermelon mosaic virus 1 (also known as Papaya ringspot virus - type W). These two potyvirus species could be distinguished serologically and by nucleotide sequences.