Fig. 2From: Identifying novel amino acid substitutions of hemagglutinin involved in virulence enhancement in H7N9 virus strainsVirus quantification. (a) Absolute RNA amounts in viruses from supernatants or cells, quantified by quantitative PCR; (b) The virulence of viruses (from supernatants or cells) in MDCK cells was quantified by measuring TCID50Back to article page