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. 2013 Oct 16;209(9):1343–1353. doi: 10.1093/infdis/jit554

Figure 1.

Figure 1.

Infection of BALB/c mice with A/Anhui/1/2013 (H7N9) influenza virus causes acute lung injury and characteristics that closely resemble acute respiratory distress syndrome (ARDS). A, Lung-weight to body-weight ratios. B, Wet-to-dry lung weight ratios. C, Pulmonary vascular permeability index. The lungs were collected 3 days postinfection (p.i.) from mice (n = 2) inoculated with 102–106 plaque-forming units (PFU)/mouse of A/Anhui/1/2013 (H7N9) influenza virus or mock. Increased ratio indicates pulmonary edema (fluid accumulation in lungs). The amount of Evans blue dye measured in pulmonary tissues was normalized to lung tissue weight [15]. D, Oxygenation level. BALB/c mice (n = 3) were infected intranasally with 102.5 PFU/mouse of A/Anhui/1/2013 (H7N9) virus, and arterial blood was drawn 3, 6, or 9 days p.i. Oxygenation level was determined as a ratio of arterial partial pressure of oxygen (PO2) to fraction of inspired oxygen (FIO2) using the i-STAT CG8+ system. Ratios ≤300 and ≤200 indicate mild and moderate ARDS, respectively, as defined by the ARDS working group [18]. *P < .0001, by unpaired Student t test.