Figure 4.

Lung injury by subsequent H1N1 infection was enhanced in the SARS-CoV-2 infection convalescent stage. (a) The lung injury by subsequent H1N1 infection were detected by HE staining, and in the early stage, inflammatory cells infiltrated around bronchioles or blood vessels, and then the cells in bronchi began to die and occlude the bronchi, in the last phase, large areas of pulmonary stroma were substantial lesions with inflammatory cell infiltration and alveolar cell shedding and death, and in the lungs of the mice without SARS-CoV-2 infection, the areas of substantial lesions were smaller than those in the mice infected with SARS-CoV-2 for 7 and 14 days. In addition, some alveolar septal cells thickened in the mice that had been infected with SARS-CoV-2. (b) Scoring of histopathological changes to quantify the lung injury, including Pulmonary oedema scores, Alveolar infiltration scores and Bronchia infiltration scores. The Histology score standards were in sTable 1. n = 3 in every point and the data were analysed using GraphPad Prism 8, and the P-values were calculated by one-way ANOVA using SPSS PASW statistical software version 18.0. *0.01 < P ≤ 0.05, **0.001 < P ≤ 0.01 and ***P ≤ 0.001.