KRAS and infection: All viruses resulted in morbidity/mortality within 7–8 days post-infection (dpi) and no significant difference (p>0.1) in the calculated lethal dose 50% (LD50) was observed between the parental (NS3-249P) and mutant viruses with, LD50 values calculated between 0.3 and 0.6 plaque forming units (PFU).