This activation process is orchestrated through cooperative actions within the host protease network, including human airway trypsin-like protease (HAT, also referred to as TMPRSS11D) (59, 60, 63), TMPRSS2 (58–62), TMPRSS4 (64, 65), TMPRSS11A (66), and matriptase (ST14 gene) (65, 67–70) (Figure 2A), which catalyze HA cleavage on the cell membrane surface to induce fusogenic conformational changes, thereby facilitating infection across diverse influenza subtypes. The gene discussed is TMPRSS2; the disease is infection.