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Published on: February 16, 2022
Slow Spread of SARS-CoV-2 in Southern Brazil Over a 6-Month Period: Report on 8 Sequential Statewide Serological
Pedro C Hallal1, Mariângela F Silveira1, Ana M B Menezes1
1Pedro C. Hallal, Mariângela F. Silveira, Ana M. B. Menezes, Bernardo L. Horta, Aluísio J. D. Barros, Nadege Jacques, Luís Paulo Vidaletti, Fernando P. Hartwig, Fernando C. Barros, and Cesar G. Victora are with the Postgraduate Program in Epidemiology, Universidade Federal de Pelotas, Brazil. Lúcia C. Pellanda and Helena Schirmer are with the Universidade Federal de Ciências de Saúde de Porto Alegre, Brazil. Gabriel D. Victora is with the Laboratory of Lymphocyte Dynamics, Rockefeller University, New York, NY. Odir A. Dellagostin is with the Postgraduate Program in Biotechnology, Universidade Federal de Pelotas. Claudio J. Struchiner is with the Fundação Getúlio Vargas, Rio de Janeiro, Brazil. Marcelo N. Burattini is with the Universidade Federal de São Paulo, Brazil. Marilia A. Mesenburg is with the Postgraduate Program in Epidemiology, Universidade Federal de Pelotas, and the Universidade Federal de Ciências de Saúde de Porto Alegre. Emanuele L. Ambros is with the Secretaria Municipal de Saúde de Uruguaiana, Brazil. Evelise M. Berlezi is with the Universidade de Ijuí, Brazil. Jane D. P. Renner is with the Universidade de Santa Cruz do Sul, Brazil. Kaue Collares is with the Universidade de Passo Fundo, Brazil. Maria Letícia R. Ikeda is with the Universidade do Vale do Rio dos Sinos, Sao Leopoldo, Brazil. Thiago M. Ardenghi is with the Universidade Federal de Santa Maria, Brazil. Patricia de Gasperi is with the Universidade de Caxias do Sul, Brazil.
Abstract:
Objectives. To evaluate the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) over 6 months in the Brazilian State of Rio Grande do Sul (population 11.3 million), based on 8 serological surveys. Methods. In each survey, 4151 participants in round 1 and 4460 participants in round 2 were randomly sampled from all state regions. We assessed presence of antibodies against SARS-CoV-2 using a validated lateral flow point-of-care test; we adjusted figures for the time-dependent decay of antibodies. Results. The SARS-CoV-2 antibody prevalence increased from 0.03% (95% confidence interval [CI] = 0.00%, 0.34%; 1 in every 3333 individuals) in mid-April to 1.89% (95% CI = 1.36%, 2.54%; 1 in every 53 individuals) in early September. Prevalence was similar across gender and skin color categories. Older adults were less likely to be infected than younger participants. The proportion of the population who reported leaving home daily increased from 21.4% (95% CI = 20.2%, 22.7%) to 33.2% (95% CI = 31.8%, 34.5%). Conclusions. SARS-CoV-2 infection increased slowly during the first 6 months in the state, differently from what was observed in other Brazilian regions. Future survey rounds will continue to document the spread of the pandemic.
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