Our metabolomics study revealed common metabolic signatures affecting all COVID-19 patients and emphasized the major changes to affect the moderate and severe conditions . In particular , our data did not reveal huge alterations in mild patients compared to healthy individuals , suggesting that SARS - CoV-2 infection that induces mild symptoms does not substantially affect the serum metabolome and related metabolic pathways in these patients . Instead , the prevalent differences appear evident in the moderate condition , and are maintained in the severe one . In accordance with the trend of these findings , in a multi - omics study , a high similarity between moderate and severe COVID-19 and a major sharp shift between mild and moderate disease [ 31 ] was identified , which would be responsible for the key differences found in the serum metabolome of our patients ' cohort .