Viral dynamics in asymptomatic patients with COVID-19

Abstract

Data are limited on the viral load, viral shedding patterns, and potential infectivity of asymptomatic patients (APs) with coronavirus disease 2019 (COVID-19). This study included 31 adult patients who were virologically confirmed to have COVID-19 but were asymptomatic on admission. Among these 31 patients, 22 presented symptoms after admission and were defined as asymptomatic patients in the incubation period (APIs); the other nine patients remained asymptomatic during hospitalization and were defined as asymptomatic patients (APs). The median cycle threshold (Ct) value of APs (39.0, interquartile range (IQR) 37.5-39.5) was significantly higher than that of APIs (34.5, IQR 32.2-37.0), indicating a lower viral load in APs. However, the duration of viral shedding remained similar in the two groups (7 days, IQR 5-14 days vs. 8 days, IQR 5-16 days). The study findings demonstrated that although APs with COVID-19 have a lower viral load, they still have certain period of viral shedding, which suggests the possibility of transmission during their asymptomatic period. Further longitudinal surveillance of these asymptomatic cases via virus nucleic acid testing are warranted.

Keywords: Asymptomatic patients; COVID-19; Viral load; Viral shedding.

Figure 1

Viral shedding patterns and pulmonary symptoms progression of 31 asymptomatic patients during hospitalization. *Tested SARS-COV-2 RNA positive before admission. The numbers on the top indicate the number of days since admission. APs: patient 1–9; APIs: patient 10–31. Abbreviations: AP, asymptomatic patient; API, asymptomatic patient in incubation period.

Figure 2

Viral dynamics in asymptomatic patients with COVID-19. The figure shows the viral dynamics of included APs and APIs infected with COVID-19, and each line represents a patient. Figure 2A shows available Ct values from 5 APs and 14 APIs with COVID-19 at different stages of hospitalization. The solid lines in black show the normal limit of Ct values. Median, quartile 1, and quartile 3 are shown. Figure 2B shows the Ct values of serial samples from 5 APs and 14 APIs with COVID-19. *P values < 0.05. Abbreviations: Ct, cycle threshold; AP, asymptomatic patient; API, asymptomatic patient in incubation period.