In comparison to 48 hr titers, A/Victoria/3/75 titers at both temperatures and A/Dk/Eng/62 titers at 37uC were reduced at 72 hr pi and every time point thereafter, indicating reduced progeny virus production. A loss of titer was also observed for A/ Dk/Eng/62 at 32uC, but not before 120 hrs pi. To determine if loss of titer after reaching maximum levels correlated with increased CPE, we quantified adenylate kinase (AK) release by dead/dying cells into the apical compartment as a sensitive and global measure of cytotoxicity across the entire epithelial cell