Comparison of virus titers in blood, lungs, liver, kidney and spleen
after infection with mouse passaged (MP) viruses. MP30 showed similar
significance against MP20 and plaque purified MP30 (MP30pp) virus in kidney
tissue. All mice were challenged with 10^6.5 CCID50 of the
respective viruses in a 90 μl volume. *P<0.05,
**P<0.01, ***P<0.001.