SARS-CoV-2 seroprevalence and associated factors in Manaus, Brazil: baseline results from the DETECTCoV-19 cohort study

Background: Twice city of Manaus located in the Brazilian rainforest, has experienced a health system collapse due to the SARS-CoV-2 pandemic. However, little is known about which groups among the general population have been more affected. In this report, we present the overall prevalence of SARS-CoV-2 infection and associated factors from the DETECTCoV-19 cohort. Methods: A convenience sampling strategy via online advertising recruited 3046 adults. Sociodemographic characteristics, COVID-19-related symptoms, COVID-19 testing, self-medication and prescribed medications were recorded. Serum anti-SARS-CoV-2 nucleocapsid IgG antibodies were measured with an in-house ELISA. Prevalence ratios (PR) were obtained using cluster-corrected and adjusted Poisson’s regression models. Findings: A crude positivity rate among asymptomatic and symptomatic individuals, was estimated at 29·10%, with a maximum seroprevalence of 41·53% corrected by test characteristics and an antibody decay rate of 27%. Regression models demonstrated a strong association towards marginalized low-income and vulnerable residents with limited health access. Presence of a COVID-19 case (PR 1·39, 1·24-1·57) or death (PR 2·14, 1·74-2·62) in a household increased greatly the risk of other household members acquiring infection. SARS-CoV-2 seroprevalence was higher among those who self-medicated to prevent infection (PR 1·36, 1·27-1·46). Interpretation: High SARS-CoV-2 seropositivity reveals a much burdensome scenario than estimations based on confirmed COVID-19 cases in Manaus. Overall, prevalence of SARS-CoV-2 antibody response demonstrated a disproportionate social and economic disparity among the study participants. The syndemic nature of COVID-19 in the Amazon region needs differential policies and urgent solutions to control the pandemic. Funding: Research was funded by Ministry of Education (MEC), Brazil. BBS, IVPF, ROS, ARCB and WBSS received scholarship from CAPES. DSSS, TBNM, MFF and NOC received scholarship from FAPEAM Declaration of Interests: The authors declare no conflict of interest. Ethics Approval Statement: The research ethics committee of Federal University of Amazonas (UFAM) approved this study (CAAE:34906920·4·0000·5020) in accordance with Brazilian law