A method for diagnosing COVID-19 infection of a person. The method includes acquiring a sputum sample of the person, measuring a level of reactive oxygen species (ROS) in the sputum sample, and detecting a COVID-19 infection status of the person based on the measured level of ROS. Measuring the level of ROS in the sputum sample includes recording a cyclic voltammetry (CV) pattern from the sputum sample and measuring a current peak of the recorded CV pattern. Detecting the COVID-19 infection status of the person based on the measured level of ROS includes detecting the person is infected with COVID-19 if the measured current peak is in a first range of current peaks and detecting the person is not infected with COVID-19 if the measured current peak is in a second range of current peaks.