COPD:Chronic Obstructive Pulmonary Disease;InfAH1N1:Seasonal Influenza A virus H1N1;HRV: Human Rhinovirus;HADV:HumanAdenovirus;InfAH3N2:Seasonal Influenza virus H3N2;InfB:Seasonal Influenza B virus;ICU:intensive care unit;WBC:white blood count;NLR:neutrophil:lymphocyte ratio;PCT:procalcitonin ;PLT:platelet；ALT:glutamic-pyruvic transaminase；AST:glutamic-oxalacetic transaminase;CB:direct bilirubin

;IBIL:indirect bilirubin;Cr =:creatinine;CD4：CD4 T-cell；CD8：CD8 T-cell;G^-:gram-negative bacterium;G⁺:gram-positive bacterium ;ICU:intensive care unit. PCR etiology was carried out in our hospital since January 2019.