Whole-CCHFV-virion-specific IgM and IgG responses in serum were quantified by an in-house ELISA as previously described 23 (link). To measure NP or Gc specific responses we performed a sandwich ELISA. Nunc Maxisorp plates were coated with 200ng/well of mouse monoclonal antibodies against NP (clone 9D5, BEI Resources) or Gc (11E7, BEI resources). Plates were then blocked with 5% skim milk in PBS 0.05% Tween and then semi-purified whole virus lysate 23 (link) applied. Plates were washed and a 1:1000 dilution of serum applied. Bound antibodies were detected with goat horseradish peroxidase conjugated anti-monkey IgG (Seracare, catalog KPL 074–11-021) at 1:2000 and plates developed with ABTS solution (Seracare). Development was stopped with 5% sodium dodecyl sulfate in water and absorbance at 405nm read on a Synergy HTX (Biotek). For data analysis, absorbance values of wells coated with anti-NP or anti-Gc but receiving no CCHFV lysate were subtracted from wells receiving lysate. All measurements were performed in duplicate.