The influenza virus used in the direct challenge AI study was A/Turkey/CA/D0208651-C/02 H5N2 low pathogenic. Influenza A/Turkey/Wisconsin/1/1966 H9N2 low pathogenic was used for hyperimmune serum production provided by Charles River Avian Vaccine Services (Storrs, CT). Viruses were grown and titered in 9-to 11-dayold embryonated specific pathogen-free (SPF) chicken eggs as previously described [24] .