The presence of 5′ triphosphate viral RNA in the cytosol during Influenza infection triggers RIG-I activation; while TLR3 and TLR7 recognise the presence of influenza double stranded or single stranded RNA in the endosome, triggering signalling cascades that culminate in the upregulation of pro-IL-1β, pro-IL-18 and other pro-inflammatory cytokines [35]. Here, TLR3 is linked to influenza.