The epidemiologic data revealed that most COVID-19 transmission occurred through contact within 3 to 5 days or less from the symptom onset. However, epidemiologic data are prone to recall and misclassification bias; therefore, laboratory data, including viable viral shedding kinetics, can complement these epidemiologic observations and provide important insight in terms of isolation policy and treatment duration of antiviral therapy. The studies revealed that asymptomatic patients with Severe Acute Respiratory Syndrome-Coronavirus-2 (SARS-CoV-2) infection had a similar viral load to symptomatic patients during the early course of the disease but exhibited a more rapid decrease in viral load with the loss of infectivity. Furthermore, symptomatic patients with COVID-19 had high infectivity and high symptom scores during the early course of the disease and gradually lost infectivity and symptom severity. In addition, the studies on the effect of COVID-19 vaccination on viral load kinetics showed that fully vaccinated individuals had a shorter duration of viable viral shedding and a lower secondary attack rate than partially vaccinated or unvaccinated individuals. Furthermore, the more recent variants, such as Omicron had a shorter viable viral shedding time (median 3-5 days from the symptom onset) than the precedent variants, such as Delta (median 8.5 days from the symptom onset). Furthermore, immunocompromised patients with COVID-19 tended to shed viable viruses for a prolonged period of up to a median of 4 weeks from the symptom onset.

Keywords: SARS-CoV-2, COVID-19, Viral shedding kinetics