The five health care personnel had been definitively seronegative versus H5 in all assays, which suggests they weren't infected with H5. Hemagglutinin inhibition (HI) assay: The HI assay tests for antibodies to the hemagglutinin of the specific influenza virus using red blood cells (RBC). Multiple types of RBCs were assessed https://www.dailypioneer.com/2024/india/tripura-to-extend-successful-rubber-mission.html