18 May 2021

This is the main finding of a study.The authors analyzed blood samples collected in a town in the Brazilian Amazon before and after the first wave of the pandemic to detect the presence of antibodies against dengue virus and SARS-CoV-2.

A study published this May in the journal Clinical Infectious Diseases suggests that people who have had dengue in the past are twice as likely to develop symptoms of COVID-19 if they are infected by the novel coronavirus.

The findings of the study were based on an analysis of blood samples from 1,285 inhabitants of M?ncio Lima, a small town in the state of Acre, part of Brazil?s Amazon region. The principal investigator was Marcelo Urbano Ferreira, a professor at the University of S?o Paulo?s Biomedical Sciences Institute (ICB-USP) in Brazil. The study was supported by FAPESP.

?Our results show that the populations most exposed to dengue, possibly owing to socio-demographic factors, are precisely those that most risk falling very sick if they?re infected by SARS-CoV-2. This is an example of what has been called a syndemic [synergic interaction between two epidemic diseases so that one exacerbates the effects of the other]. On one hand, COVID-19 has hindered efforts to control dengue. On the other, the latter appears to increase the risk for those who contract the former,? Ferreira told Ag?ncia FAPESP.

For seven years Ferreira has been conducting research in M?ncio Lima with the aim of combating malaria. In 2018 he began work on a project involving a survey of 20% of the town?s population every six months. His team call on homes, apply questionnaires, and collect blood samples. In early 2020 the project received additional funding from FAPESP so that part of the research effort could be redirected to the monitoring and characterization of SARS-CoV-2 in the region (read more at: agencia.fapesp.br/34728).

?In September 2020, a study by another group was published suggesting that areas with many cases of dengue were relatively little affected by COVID-19. Because we already had blood samples collected from inhabitants of M?ncio Lima before and after the first wave of the pandemic, we decided to use the material to test the hypothesis that prior infection by dengue virus conferred some degree of protection against SARS-CoV-2. What we found was exactly the opposite,? Ferreira said.

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