3.5 Acid stability
Resistance to low pH is crucial for influenza viruses to survive in the environment (Scholtissek, 1985). To understand the acid stability of these two isolates, both strains were treated in solution with different pH values and then virus titers were determined by TCID50 on MDCK cells. The results (Figure 3C) showed that both viruses presented a quite high replication capacity until treatment with pH 5.4, indicating they were relatively stable in acidic environment.