To test our hypothesis that specific cathepsins and extracellular vesicle (EV) enriched proteins can serve as urinary biomarkers after COVID-19 infection, we used urine samples from COVID-19-negative participants and COVID-19-positive participants to measure the activity of various cathepsin proteases and isolate urinary EVs (uEVs) for downstream proteomics analysis. The gene discussed is CTSS; the disease is COVID-19.