IL6 and COVID-19: In the rectal swabs, the bacterial species Hungatella hathewayi and Eggerthella lenta were enriched in the COVID-19 patients compared to healthy controls, and we observed a strong positive correlation between the relative abundance of Hungatella hathewayi and IL-6 plasma concentrations (r = 0.8, P = 0.003; Fig. 7A), though there were no significant correlations observed between the relative abundance of Eggerthella lenta and any plasma biomarkers.