Fig. 2.

The PsiI enzyme cleavage site (shaded) and the exact location of the genetic marker (red) that allows the differentiation of wild-type viruses from the vaccine strains. The nucleotide position number corresponds to the position in the H gene sequence of the Onderstepoort reference strain (AF378705, Onderstepoort strain; AF259552, Snyder Hill strain; Z35493, Convac strain; AB212966, Vaccine strain, Japan; DQ903854, Lederle strain). One wild-type genotype from each branch of the phylogenetic tree (Fig. 3) is represented.