Mice were challenged with 100 PFU of CCHFV strain IbAr 10200 or Afg09-2990 by the subcutaneous (IFNAR−/−) or intraperitoneal (all other mice) route, as indicated. Virus was diluted in a total volume of 0.2 ml of PBS (Gibco). All mice except IFNAR−/− were intraperitoneally injected with 2.5 mg of anti-IFNAR 1 (mAb-5A3; Leinco Technologies Inc.) diluted in PBS 24 hours after infection in a total volume of 0.4 ml. For antibody injections, as indicated, mice were injected subcutaneously or intraperitoneally with 1 mg per antibody per dose in a total volume of 0.2 ml diluted in PBS.