Innate immune receptor which acts as a cytoplasmic sensor of viral nucleic acids and plays a major role in sensing viral infection and in the activation of a cascade of antiviral responses including the induction of type I interferons and pro-inflammatory cytokines (PubMed:28594402, PubMed:32169843, PubMed:33727702). Its ligands include mRNA lacking 2'-O-methylation at their 5' cap and long-dsRNA (>1 kb in length) (PubMed:22160685). Upon ligand binding it associates with mitochondria antiviral signaling protein (MAVS/IPS1) which activates the IKK-related kinases: TBK1 and IKBKE which phosphorylate interferon regulatory factors: IRF3 and IRF7 which in turn activate transcription of antiviral immunological genes, including interferons (IFNs); IFN-alpha and IFN-beta. Responsible for detecting the Picornaviridae family members such as encephalomyocarditis virus (EMCV), mengo encephalomyocarditis virus (ENMG), and rhinovirus (PubMed:28606988). Detects coronavirus SARS-CoV-2 (PubMed:33440148, PubMed:33514628). Can also detect other viruses such as dengue virus (DENV), west Nile virus (WNV), and reovirus. Also involved in antiviral signaling in response to viruses containing a dsDNA genome, such as vaccinia virus. Plays an important role in amplifying innate immune signaling through recognition of RNA metabolites that are produced during virus infection by ribonuclease L (RNase L). May play an important role in enhancing natural killer cell function and may be involved in growth inhibition and apoptosis in several tumor cell lines. {ECO:0000269|PubMed:14645903, ECO:0000269|PubMed:19211564, ECO:0000269|PubMed:19656871, ECO:0000269|PubMed:21217758, ECO:0000269|PubMed:21742966, ECO:0000269|PubMed:22160685, ECO:0000269|PubMed:28594402, ECO:0000269|PubMed:28606988, ECO:0000269|PubMed:29117565, ECO:0000269|PubMed:33440148, ECO:0000269|PubMed:33514628, ECO:0000269|PubMed:33727702}. This is the function of Ensembl gene identifier ENSG00000115267 (IFIH1, interferon induced with helicase C domain 1).