Data availabilityCryo-EM density maps and atomic coordinates generated in this study have been deposited in the Electron Microscopy Data Bank (EMDB; https://www.ebi.ac.uk/emdb/) and the Protein Data Bank (PDB; https://www.rcsb.org/) under the following accession numbers: apo CCHFV-L (EMD-66754, PDB 9XD4); 5′ vRNA bound CCHFV-L complex (EMD-66755, PDB 9XD5); 3′ vRNA bound CCHFV-L complex (EMD-66756, PDB 9XD6); CCHFV-L elongation complex containing a 9-bp RNA product (EMD-66787, PDB 9XEC); CCHFV-L elongation complex containing a 15-bp RNA product (EMD-66785, PDB 9XE9); CCHFV-L elongation complex containing a 10-bp RNA product and incorporated 2FC (EMD-66783, PDB 9XE6) and CCHFV-L elongation complex containing a 10-bp RNA product and incorporated cytidine (EMD-66784, PDB 9XE7). KASV endonuclease-WXSH0208 complex (PDB 9XF9). Previously published structures used in this study are available in the PDB under the following accession numbers: 1S76, 4WSB, 5AMP, 5UJ2, 6FS6, 6L42, 6Y6K, 6Z8K, 7BV2, 7KL3, 7OJL, 7OJN, 7ORL, 7ORM, 8AS7, 8ASD, 8C4T, 8KI7, 8KI9, 8P1L, 8PNQ, 8QGU, 8R6W, 8R6Y, 8Z9R, 9GJU. Uncropped gel images are included as Supplementary Fig. 13. Source data are provided with this paper.ReferencesErgönül, Ö. Crimean–Congo haemorrhagic fever. Lancet Infect. Dis. 6, 203–214 (2006).Article