Number and percent of live poultry market workers and non-poultry worker controls whose serum tested positive for neutralizing antibody against H5 viruses.

aSera were considered positive for antibody to an H5 virus if a titer of ≥40 was obtained in two independent assays and tested positive by Western immunoblotting for reactivity with purified H5 HA.bSera from 5 individuals in the poultry market worker group were seropositive for neutralizing antibody to HK/156/97 and HK/213/03 viruses.cSera from the same 2 individuals from the control group were seropositive for neutralizing antibody to HK/156/97 and HK/213/03 viruses.*Fischer's Exact Test.