Mortality data for SCID/ICR mice inoculated with viruses containing substitutions at position 326. The experimental procedures were carried out as described in Materials and Methods. Groups of 10 mice per virus were tested. The P values for mortality rates at 50 days were as follows, with a P value of <0.05 considered significant: 326E versus 326S or 326A, P = 0.473; 326E versus 326G, P = 0.999; 326E versus 326Q, P = 0.210; 326E versus YF5.2iv, P = 0.003; 326E versus 326R, P = 0007; 326Q versus YF5.2iv, P = 0.178; 326Q versus 326R, P = 0.069; 326Q versus 326A or 326S, P = 0.999; YF5.2iv versus 326R, P = 0.999. The average survival time data in days (mean ± standard deviation, median) were as follows: 326E, 17.7 ± 4.9, 16; 326D, 22.6 ± 18, 16; 326S, 23.7 ± 2.8, 25; 326A, 25 ± 17.9, 18; 326Q, 55.1 ± 63.6, 17; 326G, 69 ± 55.3, 52.5; 326R, 87.5 ± 2.5, 90; YF5.2iv, 66.6 ± 23.2, 75. P values (two sided) for comparison of the average survival times (log rank test), with a P value of <0.05 considered significant, were as follows: 326E versus 326D, 0.810; 326E versus 326Q, 307; 326E versus 326A, 0.167; 326E versus 326G, 0.103; 326E versus 326S, 0.026; 326D versus 326Q, 0.222; 326D versus 326A, 0.193; 326D versus 326G, 0.094; 326D versus 326G, 0.047; 326S versus 326Q, 0.645; 326S versus 326G, 0.502; 326S versus 326A, 0.002; 326A versus 326Q, 0.681; 326A versus 326G, 0.502; 326Q versus 326G, 0.880.