Intra-Familial Transmission Patterns of COVID-19 Infection among the Rural Residents of Ahmedabad, Gujarat, during an Epidemic of SARS-CoV-2 in India.

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.