Virus-derived epitopes are useful tools to accurately evaluate immune response and to differentiate which responses are specific or due to cross-reactivity [24, 25, 26] . Several studies have reported the existence of HA subtype-specific as well as inter subtypeconserved epitopes [27, 28, 29] . ELISA assays based on epitopes that are highly conserved and specific for one certain HA subtype will be useful for rapid and simple subtyping of IAVs. Such epitopes in IAVs have not been fully addressed although many studies have been performed. In the present study, we report the successful identification of a new epitope, which is highly conserved among the majority of IAV strains of H1 subtype. Moreover, we developed an ELISA assay for H1 antibody subtyping based on this epitope. Results derived from this new assay correlate with results obtained through the use of HI test.