Fig 1.

Viral growth kinetics in MDCK cells (A) and normal human alveolar epithelial cells (B). Cells were infected with Norway3568 or Norway3487 at a multiplicity of infection of 0.001. At different times postinfection, virus titers in the supernatants of infected cells were determined by use of plaque assays in MDCK cells. The mean from triplicate independent cultures ± standard deviation is shown. The mean titers of Norway3487 virus were significantly higher than those of Norway3568 virus (*, P < 0.001; **, P < 0.01).