ðɛɹˌɑːɹ sˈɛvɹəl nˈeɪmd stɹˈeɪnz ʌv ˌɛktɹoʊmˈiːliə vˈaɪɹəs ðæt vˈɛɹi ɪn vˈɪɹələns, ɪŋklˈuːdɪŋ ˌɛnˌaɪˈeɪtʃ sˈɛvənti nˈaɪn, wˈɑːʃjˈuː, mˈɑːskoʊ, hˈæmpstɛd, sənt. lˈuːi sˈɪksti nˈaɪn, beɪdʒˈɪŋ sˈɛvənti, ænd ˌɪʃɪbˈæʃi aɪ ɹˌoʊmən θɹˈiː.
There are several named strains of ectromelia virus that vary in virulence, including NIH-79, Wash-U, Moscow, Hampstead, St. Louis-69, Beijing-70, and Ishibashi I–III.