Inhibition of TrkA signaling by the TrkA inhibitor GW441756 was shown to significantly reduce viral production by ~ 2 logs in A549 cells infected with A/CA04 at both MOI of 0.1 and 0.01 (Fig 1C), consistent with our previous findings for A/WSN, A/PR8, A/x31 (H3N2), or B/Victoria infection of A549 cells [10,11]. Here, NTRK1 is linked to infection.