Phylogenetic relationships among 73 CDV isolates based on the amino acid sequences of the H gene. Distance values were calculated by the ClustalW program within the MEGA 5.0 software package. The Neighbor-Joining algorithm was used to generate the tree. Bootstrap values were calculated on 1000 replicates. Only bootstrap values >75% were shown. Filled quadrate (■) indicates the 8 Chinese wild-type CDV strains analyzed in this study.