Researchers track genetic changes in Brazil's rare Sabiá virus

The Sabiá virus causes an acute hemorrhagic and neurological syndrome. Four fatal cases have been recorded in the state of São Paulo since 1990. The virus has been circulating in Brazil for about 142 years. Genomic analyses of two cases recorded in 2019 and 2020 show that the virus has undergone genetic changes over time, which explains why it was not identified by existing tests.

The team developed primers – small DNA fragments used to detect the virus in laboratory tests – and sent them to the Adolpho Lutz Institute in São Paulo, the state's leading facility for this type of testing.

The genomes recovered from Sabiá were approximately 89% genetically identical to strains previously described in 1999, when the second case in history was recorded. "When analyzing the genomes of the new cases, we identified mutations in target regions of the primers that prevented detection by existing diagnostic tests. We modified those regions, and now it's possible to identify the circulating strains," Claro explains.

How the virus interacts with human cells

The man, who had a history of hiking in forested areas, sought care at a primary care clinic on December 30, 2019. He was then transferred to FM-USP's general and teaching hospital (Hospital das Clínicas) in São Paulo with a suspected case of yellow fever and died on January 11, 2020. Initial tests were negative for yellow fever and Sabiá virus.

After detecting the virus in subsequent tests, the researchers analyzed blood samples from seven previous cases of acute hemorrhagic and neurological syndrome that had tested negative for yellow fever. They found a case involving a 63-year-old rural worker from Assis who was admitted to the Hospital das Clínicas on December 10, 2019, and died two days later.

In both cases, the researchers observed changes in the protein that allow the virus to bind to human cells. Phylogenetic analyses, which allow for the reconstruction of the evolutionary history of a virus, indicated that the pathogen has been circulating in Brazil for decades and is likely not a recent introduction.

Ester Sabino, professor at FM-USPThere were likely other cases in the past that went unidentified. It's important to understand the virus, develop tests, and study the changes occurring in its genome so that we can anticipate future cases, and even outbreaks, of the disease."

The species that serves as a reservoir for the virus is not yet known, but it is believed to be wild rodents. The infections occurred in rural areas where wild animals and humans may interact.

Source:Journal reference: