We initially conducted experiments with mucin extracts from porcine stomach (Type II, Sigma-Aldrich). Results indicated that IAV infection was blocked, probably by the bound sialic acid on the mucin. Similarly, glycans on human mucus could prevent IAV attachment to the cell in the TCID50 assay. However, such an effect was not significant according to our experiment. The titer of IAV spiked in the human mucus specimen was 5.1±2.6×107 TCID50 ml−1 after being kept on ice for 2 h, with a spiking titer of 1.78×108 TCID50 ml−1. In addition, reporting results in mucus samples as the ratio of the recovered viability after incubation at a specific RH over the initial viability, both tested in mucus, should control for any potential blocking effect due to glycans on mucus. Therefore, results reported here reflect the effect of RH.