The spike (S) gene of the family Coronaviridae has a high degree of variation and can induce neutralizing antibody (3). Reverse transcription PCR products of the 651-bp partial S gene of PEDV and the deduced amino acid sequences were aligned by using ClustalW (www.genome. jp/tools/clustalw), and a neighborjoining tree with 1,000 bootstraps was constructed. Sequences of the S genes from this outbreak were 99.1%-100.0% homologous and had 88.7%-98.9% nt identity with all reference strains (online Technical Appendix Table 2 ), 98.5%-98.9% with Thailand strains, and 94.5%-95.1% with vaccine strain CV777. The partial S gene deduced amino acid sequences were compared and also showed a high degree of homology (98.0%-100.0%); they had 85.3%-98.7% identity with all reference strains listed in online Technical Appendix Table 2 , 98.0%-98.7% with Thailand strains, and 93.3%-94.7% with vaccine strain CV777 (data not shown).