IL6 and COVID-19: The authors observed that SIG1 and SIG4, those characterizing the COVID-19 oral microbiota, correlated with the presence of IL-6, a pro-inflammatory cytokine involved in the well-known “cytokine storm” characterizing a severe COVID-19 condition, while SIG2 and SIG3, those characterizing the healthy control oral microbiota, did not [17].