According to the pathogen identified, the RELM-β levels of patients with bacterial infection, viral infection, atypical pathogen infection, mixed pathogen infection, and unknown pathogens were 668.40 (259.10–1164.0), 407.20 (213.30–747.70), 218.40 (85.41–782.70), 232.20 (134.60–626.00), and 468.70 (186.40–797.90) pg/mL, respectively (Figure 1c). Here, RETNLB is linked to bacterial infectious disease.