The five health and fitness treatment personnel had been definitively seronegative against H5 in all assays, which implies they weren't contaminated with H5. Hemagglutinin inhibition (HI) assay: The HI assay assessments for antibodies to the hemagglutinin of the particular influenza virus applying red blood cells (RBC). Many types of RBCs https://www.dailypioneer.com/2013/avenues/2013-11-12-28059.html