Virus pH tolerance. The bar graph depicts the log reduction of each virus, with standard deviation bars, after immersion in acidic buffers ranging from pH 1 to 5 for 30 min. Only FCV was evaluated in pH 5 buffer, and MNV and HAV stocks were not evaluated at pH 4. After immersion in pH 2 buffer, no FCV plaques were detected. After immersion in pH 1 buffer, no PV plaques were observed. Initial titers were 4.8 × 107 PFU/ml for HAV, 1.1 × 109 PFU/ml for PV, 7.5 × 105 PFU/ml for MNV, and 5.8 × 107 PFU/ml for FCV (N = 3; n = 9).