Design A cross-sectional study was conducted in household members in 32 districts of Bangladesh to build knowledge on disease epidemiology and seroepidemiology of COVID-19. Objective We assessed antibody responses to SARS-CoV-2 in people between April-October, 2020. Results Nationally, we estimated a seroprevalence of 30.4% for IgG and 39.7% for IgM. In Dhaka city, seroprevalence for IgG was 35.4% in non-slum areas, while it was 63.5% in slums. In areas outside of Dhaka, the seroprevalence rate for IgG was 37.5 and 28.7%, respectively, in urban and rural areas. Between April and October, 2020, the highest seroprevalence rate (57% for IgG and 64% for IgM) was observed in August. IgM antibody was more prevalent in the younger age participants, while older participants had more frequent IgG seropositivity. Follow-up specimens from COVID-19 patients and their household members suggested that both IgG and IgM seropositivity increased significantly at day 14 and 28 compared to day 1 of enrollment. Conclusions Our findings indicate that there has been an extensive spread of SARS-CoV-2 infection in Bangladesh by October 2020. This highlights the importance of monitoring seroprevalence data, particularly with the emergence of new SARS-CoV-2 variants over time.
Seroprevalence of SARS-CoV-2 antibodies in Bangladesh related to novel coronavirus infection