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Abstract
In 2012, the United States experienced a particularly widespread outbreak of hemorrhagic disease (HD). Deer (both Odocoileus virginianus and O. hemionus) in 35 states were affected. Epizootic hemorrhagic disease virus, serotype 2 (EHDV-2) was the predominant virus isolated, representing 66% (135/205) of isolates. The large number of EHDV-2 isolates from a single outbreak provided an ideal opportunity to examine viral relatedness during the outbreak. In phylogenetic analyses of complete gene sequences from the antigen-determining and insect-binding proteins (VP2 and VP7, respectively) of 34 isolates from 21 states, we found subtle genotypes with regional associations in both proteins. This is consistent with presence of multiple strains of EHDV-2 expanding rather than a single virulent strain creating the entire outbreak. VP2 proteins shared 99.0% nucleotide identity; VP7 proteins shared 99.1% nucleotide identity. Very few changes were observed in either protein at the amino acid level.