A group of researchers in Brazil and the UK have developed a method to track seroprevalence in real time. An article in the journal eLife shows how this was done in the case of SARS-CoV-2, providing a "portrait" of the first year of COVID-19 in Brazil.
An article published in the journal eLife reports a study in which researchers concluded that the proportion of the population previously infected by SARS-CoV-2 (infection-induced seroprevalence) can be estimated using blood donation samples. The findings offer a sort of "portrait" of the first year of the COVID-19 epidemic in Brazil. According to the authors, their novel methodology can also be used to track and estimate collective immunity to other infectious diseases. The usual method of estimating seroprevalence in Brazil is based on random samples of the population. The authors note that this method is costly and hard to perform periodically in real time. Serosurveillance is important to understand the characteristics of epidemics and formulate public policy, by detecting where prevention and treatment are effective, for example. The principal authors are affiliated with the Brazil-UK Center for Arbovirus Discovery, Diagnosis, Genomics & Epidemiology (CADDE). They tested 97,950 blood donation samples for immunoglobin G (IgG) antibodies. The samples were collected in Brazil's eight most populous state capitals: Belo Horizonte, Curitiba, Fortaleza, Manaus, Recife, Rio de Janeiro, Salvador and São Paulo. The study period ran from March 2020 to March 2021. The results showed that the COVID-19 epidemic spread unevenly, affecting the populations of these cities at different times. Seroprevalence was generally highest among men and younger people. "Early on, some lines of investigation assumed everyone was infected at the same time, but we showed this wasn't the case. In terms of a portrait of the epidemic, we concluded that it was extremely heterogeneous in Brazil, with different levels of infection between groups and significant variation in lethality rates. We hadn't expected this result," Carlos Augusto Prete Junior, first author of the article, told Agência FAPESP. Prete Junior is a researcher at the University of São Paulo's Engineering School (POLI-USP).…