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Dear Editor,rnAs of 5 July,2020,approximately 20,162,000 confirmed cases of coronavirus disease 2019(COVID-19),which is caused by severe acute respiratory syndrome coronavirus 2(SARS-CoV-2),have been reported globally,including an estimated 740,000 deaths.Although the clinical manifesta-tions of COVID-19 are heterogeneous,viral infection and pathological changes in the respiratory system,especially the lungs,still represent common characteristics of COVID-19.