Modeling the early temporal dynamics of viral load in respiratory tract specimens of COVID-19 patients in Incheon, the Republic of Korea

Lim, Ah-Young; Cheong, Hae-Kwan; Oh, Yoon Ju; Lee, Jae Kap; So, Jae Bum; Kim, Hyun Jin; Han, Boram; Park, Sung Won; Jang, Yongsun; Yoon, Chang Yong; Park, Yun Ok; Kim, Jong-Hun; Kim, Jin Yong

Objective To investigate the duration and peak of severe acute respiratory syndrome coronavirus 2 shedding as infectivity markers for determining the isolation period. Methods In total, 2,558 upper respiratory tract (URT) and lower respiratory tract (LRT) specimens from 138 patients with laboratory-confirmed coronavirus disease were analyzed. Measurements of sequential viral loads were aggregated using the cubic spline smoothing function of a generalized additive model. The time to negative conversion was compared between symptom groups using survival analysis. Results In URT samples, viral RNA levels peaked on day 4 after symptom onset and rapidly decreased until day 10 for both E and RdRp genes, whereas those in LRT samples immediately peaked from symptom onset and decreased until days 15.6 and 15.0 for E and RdRp genes, respectively. Median (interquartile range) time to negative conversion was significantly longer in symptomatic (18.0 [13.0–25.0] days) patients than in asymptomatic (13.0 [9.5–17.5] days) patients. The more types of symptoms a patient had, the longer was the time to negative conversion. Conclusions The viral load rapidly changes depending on the time after symptom onset; viral shedding period may be longer with more clinical symptoms. Different isolation policies should be applied depending on disease severity.