ABSTRACT
We are yet to completely understand the transmission dynamics of coronavirus disease 2019 (COVID-19), a highly infectious disease, and research exploring the same is currently lacking. Hence, a community-based cross-sectional study was conducted to assess the intra-familial transmission pattern of COVID-19 among the rural residents of Ahmedabad, Gujarat, in relation to possible determinants, with a special focus on the viral load as an important factor. This cross-sectional study included visiting 195 families. We interviewed families with at least one case of COVID-19 infection. We recorded information about sociodemographic profiles and secondary transmission of cases. Out of the 195 families, 114 confirmed having at least one infected case within the family. Approximately 38.6% (44/114) of the index cases were asymptomatic, which was much higher than the low viral load index cases. Index cases with high, moderate, and low viral loads had transmitted the infection with an average of 3.3, 1.5, 0.4 secondary cases per index case, respectively. Approximately one-third of the COVID-19 cases were asymptomatic, and the affected individuals were capable of transmitting the disease within families. Moreover, index cases with a higher viral load had a higher transmission potential to generate more secondary cases, as compared to those with a low viral load.
Subject(s)
COVID-19 , Epidemics , COVID-19/epidemiology , Cross-Sectional Studies , Humans , SARS-CoV-2 , Viral LoadABSTRACT
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.