Virulence of two H5N8 wild-type and their corresponding rescued recombinant viruses in mice. Six-week-old female BALB/c mice were intranasally inoculated with 103.0 EID50 or 106.0 EID50 of each indicated virus or 50 μL of PBS as controls. A Average body weight of surviving mice in each group (n = 5/group) up to 14 dpi are represented as percentages of the original weight on day 0. The error bars represent standard deviations (SD). B Survival rate of mice infected with indicated viruses.