RNA-dependent RNA polymerase, which is responsible for the replication and transcription of the viral RNA genome using antigenomic RNA as an intermediate (By similarity). During transcription, synthesizes subgenomic RNAs and assures their capping by a cap-snatching mechanism, which involves the endonuclease activity cleaving the host capped pre-mRNAs. These short capped RNAs are then used as primers for viral transcription. Cleaves ssRNA substrates but not DNA (By similarity). Seems to downregulate the expression of its own and heterologous mRNAs through its endonuclease activity (By similarity). a ribonucleoside 5'-triphosphate + RNA(n) = diphosphate + RNA(n+1) For endonuclease activity. Binds 2 Mn2+ ions in the active site. The divalent metal ions are crucial for catalytic activity (PubMed:31948728). For polymerase activity. Interacts with the viral nucleoprotein. The N-terminus contains the endonuclease activity (endoN) (By similarity). The central region contains the RdRp activity (By similarity). The C-terminus contains the cap-binding region (By similarity). Classified as His(+) endonuclease since it has a histidine upstream of the active site that coordinates the first cation. Belongs to the Bunyavirales RNA polymerase family.