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. 2021 Jul;14(7):845-851.
doi: 10.1016/j.jiph.2021.05.003. Epub 2021 May 27.

Epidemiological feature, viral shedding, and antibody seroconversion among asymptomatic SARS-CoV-2 carriers and symptomatic/presymptomatic COVID-19 patients

Yi Chen  1 , Ping Li  2 , Yibo Ding  2 , Miao Liu  3 , Leijie Liu  3 , Bo Yi  1 , Ting Wu  2 , Hongjun Dong  1 , Xuying Lao  1 , Keqing Ding  1 , Haibo Wang  1 , Dongliang Zhang  1 , Xiaojie Tan  2 , Zhongfa Wang  3 , Guozhang Xu  4 , Guangwen Cao  5
Affiliations

Epidemiological feature, viral shedding, and antibody seroconversion among asymptomatic SARS-CoV-2 carriers and symptomatic/presymptomatic COVID-19 patients

Yi Chen et al. J Infect Public Health. 2021 Jul.

Abstract

Background: Novel coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is pandemic. However, data concerning the epidemiological features, viral shedding, and antibody dynamics between asymptomatic SARS-CoV-2 carriers and COVID-19 patients remain controversial.

Methods: We enrolled 193 SARS-CoV-2 infected subjects in Ningbo and Zhoushan, Zhejiang, China, from January 21 to March 6, 2020. All subjects were followed up to monitor the dynamics of serum antibody immunoglobulin M (IgM) and IgG against SARS-CoV-2 using colloidal gold-labeled and enzyme-linked immunosorbent assays.

Results: Of those, 31 were asymptomatic SARS-CoV-2 carriers, 148 symptomatic COVID-19 patients, and 14 presymptomatic COVID-19 patients. Compared to symptomatic COVID-19 patients, asymptomatic carriers were younger and had higher levels of white blood cell and lymphocyte, lower level of C-reactive protein, and shorter viral shedding duration. Conversion of IgM from positive to negative was shorter in asymptomatic carriers than in COVID-19 patients (7.5 vs. 25.5 days, P = 0.030). The proportion of those persistently seropositive for IgG against SARS-CoV-2 was higher in COVID-19 patients than in asymptomatic carriers (66.1% vs. 33.3%, P = 0.037). Viral load was higher in symptomatic patients than presymptomatic patients (P = 0.003) and asymptomatic carriers (P = 0.004). Viral shedding duration was longer in presymptomatic COVID-19 patients than in asymptomatic carriers (48.0 vs. 24.0 days, P = 0.002). Asymptomatic carriers acquired infection more from intra-familial transmission than did COVID-19 patients (89.0% vs. 61.0%, P = 0.028). In 4 familial clusters of SARS-CoV-2 infection, asymptomatic carriers were mainly children and young adults while severe COVID-19 was mainly found in family members older than 60 years with comorbidities.

Conclusion: Asymptomatic carriers might have a higher antiviral immunity to clear SARS-CoV-2 than symptomatic COVID-19 patients and this antiviral immunity should be contributable to innate and adaptive cellular immunity rather than humoral immunity. The severity of COVID-19 is associated with older age and comorbidities in familial clustering cases.

Keywords: Asymptomatic carriers; COVID-19; Intra-familial transmission; SARS-CoV-2.

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Figures

Fig. 1
Fig. 1
Temporal intervals of IgM and IgG seroconversion in asymptomatic SARS-CoV-2 carriers and in COVID-19 patients during the follow-up. IgM, immunoglobin M; IgG, immunoglobin G; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2; COVID-19, novel coronavirus disease in 2019.
Fig. 2
Fig. 2
Proportion of patients acquiring SARS-CoV-2 via intra-familial transmission in asymptomatic carriers and in COVID-19 patients. SARS-CoV-2, severe acute respiratory syndrome coronavirus 2; COVID-19, novel coronavirus disease in 2019.
Fig. 3
Fig. 3
The dynamics of IgM and IgG levels in a given COVID-19 patient in Putuo district of Zhoushan, Zhejiang, China, from February 9 to March 24, 2020. OD, optical density; CO, cut-off value; IgM, immunoglobin M; IgG, immunoglobin G; COVID-19, novel coronavirus disease in 2019.
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