To non-H7 HA proteins, H7.HK1 and H7.HK2 did not react with any of the tested non-H7 HA; H7.HK3 cross-reacted with H15N8 HA, and H7.HK4 cross-reacted with H10N8 and H15N8 HAs (Fig. 1b), which sequence-wise are the closest to H7 in group 2 influenza HA genes38. The gene discussed is HK2; the disease is influenza.