A mucus specimen was collected from an infant 1 month of age in March 2011. The mucus specimen was allowed to desiccate in a vial and was reconstructed by dissolution in MilliQ water (5% w/v). To preserve the mucus structure, we first attempted to sterilize the mucus specimen by passing it through a 0.45-µm pore size filter. The specimen was not filterable, indicating its large molecular size. Thus, the reconstructed mucus was sterilized by heating at 65°C for 30 min and was checked for potential IAV contamination by TCID50 assay. No IAV was detected, and the specimen was stored at 4°C until use.