The results showed that plasma CXCL12 levels in the moderate-to-severe RSV bronchiolitis group were significantly higher than those in the healthy control group [3146.48 (2373.99, 3516.18) vs. 1061.29 (683.40, 1846.43) pg/mL; P < 0.001] and the mild group [3146.48 (2373.99, 3516.18) vs. 1865.79 (1440.73, 2232.22) pg/mL; P < 0.001]. This evidence concerns the gene CXCL12 and respiratory syncytial virus bronchiolitis.