Baseline gut microbiome features prior to SARS-CoV-2 infection are associated with host symptoms in and post COVID-19.

The human gut microbiome varies substantially across individuals and populations and differentially tames our immunity at steady-state. Hence, we hypothesize that the large heterogeneity of gut microbiomes at steady-state may shape our baseline immunity differentially, and then mediate discrepant immune responses and symptoms when one encounters a viral infection, such as SARS-CoV-2 infection. To validate this hypothesis, we conducted an exploratory, longitudinal microbiome-COVID-19 study involving homogenous young participants from two geographically different regions in China. Subjects were recruited and sampled of fecal specimens before the 3-week surge window of COVID-19 (between December 11 and December 31, 2022) in China, and then were followed up for assessment of COVID-19 and post-COVID-19 manifestations. Our data showed that the baseline gut microbiome composition was intricately associated with different COVID-19 manifestations, particularly gastrointestinal involvement and post-COVID-19 lingering symptoms, in both an individual- and population-dependent manner. Our study intriguingly for the first time highlight that the gut microbiome at steady-state may prepare us differentially for weathering a respiratory viral infection.