The neutralization antibody titer of 1:4 was recognized as the positive criterion ,
The titers of neutralizing antibody ranged from 1:8 to 1:32 .
The neutralization antibody titer of 1:4 was recognized as the positive criterion , 8 sera samples were detected to be positive , and the positive rate was 12.9 % .
The titers of neutralizing antibody ranged from 1:8 to 1:32 .