This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. In order to facilitate the characterization of flu virus for both basic research and surveillance, we have developed a multiplexed microparticle-based assay for simultaneous antibody-based strain typing and sub-typing, as well characterization of carbohydrate receptor binding preference. The combination of immunoassay-based virus sub-typing and receptor binding phenotype measurements provides an important new tool in tracking the adaptation of avian flu strains to human hosts.