ER stress can be induced by an unfolded protein response (UPR) or by viral infection (ER overload response, EOR), which mediates multiple molecular biological processes via ER stress sensors (inositol-requiring enzyme 1, IRE1, protein kinase-like ER kinase, PERK, and activating transcription factor 6, ATF6), which participate directly or indirectly in the UPR of mammalian cells [1–3]. Here, ATF6 is linked to viral infectious disease.