Fig. 1.

Circulating CA16CC024 virus resulted in dose-related disease and mortality in newborn mice. One-day-old ICR mice were intracerebrally inoculated with increasing doses of CA16CC024, from 10^2.5 to 10^6.5 CCID₅₀ ml⁻¹ (10 µl). Survival rates and clinical scores were then monitored and recorded daily after infection. Control mice were given medium instead of virus suspension. Each group contained 8–10 mice. The results are from three independent experiments. Varying grades of clinical disease are identified as: 0, healthy; 1, lethargy and inactivity; 2, wasting; 3, limb-shake weakness; 4, hind-limb paralysis; 5, moribund or dead.