According to the methods and analyses above, the following categorical variables were entered in a backward stepwise logistic regression analysis: male; age ≥60 years; smoking history; hypertension; lymphocyte ≤ 0.8∗109/L; PO2/FiO2 ≤ 260; IL-6 ≥ 13pg/ml; IL-2R ≥ 1000pg/ml; positive sputum or sanguine culture for bacteria; fungi infection; multilobular infiltration (Table 4). This evidence concerns the gene IL6 and fungal infectious disease.