a,b, Respiratory function was monitored in live mice up to day 6 p.i. using whole-body plethysmography to measure Penh (a) and EF50 (b) in 288/330+/+ mice infected with MERS-15 (n = 9) or MERS-0 (n = 3), 288/330+/− mice infected with MERS-15 (n = 4) and C57BL/6J wild-type (WT) mice infected with MERS-15 (n = 3). Data are daily means ± s.d. Student's t-test was used to compare 288/330+/+ mice infected with MERS-15 and MERS-0 (*P < 0.05; **P < 0.01). c, Pathology of lungs from infected mice at day 3 p.i. demonstrating severe inflammation for 288/330+/+ (i) and 288/330+/− (ii) mice infected with MERS-15, and moderate inflammation for 288/330+/+ mice infected with MERS-0 (iii) and C57BL/6J WT mice infected with MERS-15 (iv). d, Pathology at day 6 p.i. infected in mice. In 288/330+/+ mice infected with MERS-15, there was severe inflammation and oedema in the large airways (i) and alveoli (ii), and hyaline membrane formation (iii). The 288/330+/− mice infected with MERS-15 exhibited severe inflammation throughout the parenchyma (iv), hyaline membrane formation (v) and perivascular cuffing (vi). The 288/330+/+ mice infected with MERS-0 (vii) and C57BL/6J WT mice infected with MERS-15 (viii) exhibited mild-to-moderate inflammation. Samples were stained with haematoxylin and eosin and are representative of at least three samples. Scale bars (c,d), 1 mm.