PPBP and infectious disease: This finding aligns with previous studies on other infectious diseases such as COVID-19 where macrophages and neutrophils were also identified as key drivers of cytokine storms.12,13 Analysis of inflammatory signatures within the identified subsets revealed distinct pro-inflammatory cytokine gene expression profiles for each inflammatory cell cluster (Fig. 2c), including CXCL1/2/3/8, S100A8/9/12, IL1RN, PPBP, etc. Moreover, we observed elevated expression of key inflammatory cytokines, including CXCL1/2/3 and S100A8/9/12, in patients with severe symptoms (Supplementary Fig. 7a).