metabolomics(11) metabolite(10) COVID-19(10) Infection(10) COVID-19 patient(7) severity(7) Patient(7) profile(7) disease severity(7) Mild(7) Disease progression(7) positive(6) Predictive(6) Host(6) metabolism(6) marker(6) Biomarker(5) 5-aminolevulinic acid(4) Asymptomatic(4) non-infected(4) change(4) Saliva.(4) correlated(4) intensity(4) Coronavirus disease 2019(4) COVID-19 group(4) risk(4) controls(4) prognostic(4) prognostic biomarker(4)