These beneficial bacteria whose role in inflammation was described above have been found to be depleted in the microbiome of COVID-19 patients (Zuo et al., 2020a), and this lower abundance of beneficial commensals may be partly responsible for the inflammation seen in COVID-19 characterized by an increase in IL-1β, IL-6, IFNγ, MCP1, and IP-10 (Tay et al., 2020). Here, CCL2 is linked to COVID-19.