Dynamics of Viral Shedding and Symptoms in Patients with Asymptomatic or Mild COVID-19

Abstract

We conducted a prospective cohort study at a community facility designated for the isolation of individuals with asymptomatic or mild COVID-19 between 10 January and 22 February 2021 to investigate the relationship of viral shedding with symptom changes of COVID-19. In total, 89 COVID-19 adult patients (12 asymptomatic, 16 presymptomatic, 61 symptomatic) were enrolled. Symptom scores, the genomic RNA and subgenomic RNA of SARS-CoV-2 from saliva samples with a cell culture were measured. Asymptomatic COVID-19 patients had a similar viral load to symptomatic patients during the early course of the disease, but exhibited a rapid decrease in viral load with the loss of infectivity. Subgenomic RNA and viable virus by cell culture in asymptomatic patients were detected only until 3 days after diagnosis, and the positivity of the subgenomic RNA and cell culture in symptomatic patients gradually decreased in both from 40% in the early disease course to 13% at 10 days and 4% at 8 days after the symptom onset, respectively. In conclusion, symptomatic patients have a high infectivity with high symptom scores during the early disease course and gradually lose infectivity depending on the symptom. Conversely, asymptomatic patients exhibit a rapid decrease in viral load with the loss of infectivity, despite a similar viral load during the early disease course.

Keywords: SARS-CoV-2; presymptomatic; subgenomic RNA; viable culture; viral shedding.

Figure 1

Summary curves of total symptoms scores in symptomatic and presymptomatic patients.

Figure 2

Summary curves of viral shedding and symptom score in patients. (a) Summary curves of viral shedding for symptomatic, presymptomatic and asymptomatic patients. (b) Summary curves of viral shedding for symptomatic + presymptomatic patients and asymptomatic patients. (c) Summary curves of symptoms core and viral shedding for symptomatic patients. (d) Summary curves of symptom score and viral shedding for presymptomatic patients.

Figure 3

Results of subgenomic RNA test for SARS-CoV-2. The subgenomic positive (red) is plotted as the genomic copy number in a sample (left y-axis), where subgenomic RNA was also detected. The subgenomic negative (black) is plotted as the genomic copy number in a sample (left y-axis), where no subgenomic RNA was detected. The subgenomic positivity (right y-axis) indicates the percentage of subgenomic RNA-positive samples among the total samples by the day. (a) Presymptomatic + symptomatic. (b) Symptomatic. (c) Presymptomatic. (d) Asymptomatic.

Figure 4

Results of cell culture for SARS-CoV-2. Red-colored dots indicate positive cell culture. The subgenomic positive (red) is plotted as the genomic copy number in a sample (left y-axis), where subgenomic RNA was also detected. The subgenomic negative (black) is plotted as the genomic copy number in a sample (left y-axis), where no subgenomic RNA was detected. The subgenomic positivity (right y-axis) indicates the percentage of subgenomic RNA positive samples among the total samples by the day. (a) Presymptomatic + symptomatic. (b) Symptomatic. (c) Presymptomatic. (d) Asymptomatic.