Fig. 1. Pathogenesis of YFV-17D infection in mice. (a) Survival of YFV-17D-infected mice. Mice (3–4 weeks old) were injected intramuscularly (IM), intraperitoneally (IP), subcutaneously (SC) or in the footpad (FP) with 10⁴ p.f.u. YFV-17D and disease onset was monitored. As moribund mice do not recover from infection, they were euthanized upon severe disease onset; therefore, data are shown as the percentage without disease. Data are from three to six mice per condition for IFNAR^+/+ (intramuscular or intraperitoneal) and IFNAR^−/− (subcutaneous or footpad). Data are from 31–53 mice per condition for IFNAR^−/− (intraperitoneal or intramuscular). Statistically significant differences between conditions were found for the following: IFNAR^−/− intramuscular versus intraperitoneal and IFNAR^−/− intramuscular and intraperitoneal versus all other conditions (P<0.005, Mantel–Cox test). (b) Percentages of mice displaying no clinical signs of disease, neurotropic disease or viscerotropic disease according to inoculation route. Data were derived from 53 intramuscularly inoculated or 31 intraperitoneally inoculated IFNAR^−/− mice. Statistically significant differences in the percentage of mice developing viscerotropic disease (P<0.0001, χ² test) and no signs of disease (P = 0.006, χ² test) existed for intramuscularly versus intraperitoneally injected mice as indicated by asterisks. ns, Not significant. (c) Spleen pathology, (d) liver pathology and (e) visceral pathology in the peritoneal cavity, with arrows indicating the intestine; tissues were harvested from IFNAR^−/− mice upon disease onset or from uninfected mice.