Here, we investigated whether ER stress contributes to lung fibrosis following MERS-CoV infection by analyzing the levels of ER-stress-associated genes, such as Perk, Atf4, Chop, Atf6, and X-box binding protein 1 (Xbp1) in the lungs of MERS-CoV-infected hDPP4-Tg mice and sham-infected hDPP4-Tg mice (Figure 1C). The gene discussed is XBP1; the disease is pulmonary fibrosis.