It was found that age younger than 6 years, lymphocyte counts <2.0 × 109/L, globulin < 20.0 g/L, hs-CRP > 3.0 mg/L, procalcitonin > 0.05 ng/mL, IL-10 > 5.9 pg/mL, CD4+/CD8+ T cell ratio < 0.96 and pneumonia were associated with symptomatic infection in univariate analysis. This evidence concerns the gene CD4 and infection.