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Resurgence of dengue serotype 3 could worsen outbreaks in Brazil (106 notícias)

Publicado em 23 de janeiro de 2025

The resurgence of dengue serotype 3 (DENV-3) in Brazil after 17 years may contribute to worsening new outbreaks of the disease in the country. This is because the population is not immunized against this lineage and, at the same time, serotypes 1 and 2 – DENV-1 and DENV-2 – continue to circulate.

The alert was made by researchers from the Faculty of Medicine of São José do Rio Preto (Famerp) in an article published node Journal of Clinical Virology

“The last significant DENV-3 epidemic in Brazil and, more specifically, in São José do Rio Preto, occurred more than 15 years ago [em 2007]. The DENV-1 and DENV-2 serotypes continue to circulate continuously throughout the country. If serotype 3 establishes itself again and this situation prevails [de cocirculação de variantes]this can lead to severe forms of a dengue epidemic. This is exactly the situation we are experiencing at the moment in São José do Rio Preto”, he tells FAPESP Agency Maurício Lacerda Nogueira, professor at Famerp and one of the authors of the study.

Through a project supported by FAPESP, researchers have been carrying out genomic and epidemiological surveillance of dengue fever and other arboviruses (diseases caused by viruses transmitted mainly by mosquitoes) in São José do Rio Preto for the last 20 years.

The city in the interior of São Paulo has experienced endemic circulation of dengue in recent decades, characterized by outbreaks caused by different viral serotypes.

“The average annual temperature in São José do Rio Preto is just over 25 degrees and it rains approximately 2 thousand millimeters per year. This combination of hot and humid weather creates ideal conditions for the formation of reservoirs of mosquitoes that transmit arboviruses and a suitable place for the genomic and epidemiological monitoring of arboviruses, such as dengue. And as we have been working here for a long time, we are able to make better epidemiological inferences”, explains Lacerda.

Through active surveillance of arboviruses in patients with dengue-like symptoms treated at the Hospital de Base de São José do Rio Preto and in emergency care units (UPAs), researchers observed an increase in DENV-3 cases in the city of from the end of 2023.

Thirty-one samples collected between November 2023 and November 2024 were positive for DENV-3. The most common symptoms of patients were muscle pain, headache and fever.

“Between 2023 and 2024 we had a dengue epidemic in São José do Rio Preto, caused mainly by serotypes 1 and 2. In mid-2024 DENV-1 almost disappeared, DENV-2 became the main agent and cases of DENV-3 began to rise. And today he is the main agent here in the municipality”, says Lacerda.

The last dengue outbreak in Brazil, in 2021, was caused by DENV-1, whose sequential infection with DENV-3 was shown to be associated with increased severity during a dengue epidemic, studies carried out by other groups showed.

“However, we did not observe an increase in severity among patients participating in the study we carried out”, pondered Lacerda.

Need for active surveillance

The researchers also sequenced the genome and analyzed the phylogeny of viral isolates collected from blood samples from patients with acute fever. The results of the analyzes indicated that it belongs to the same lineage as that identified in Florida, in the United States, and in the Caribbean region, and is different from the DENV-3 strains that circulated in Brazil during the 2000s.

These findings indicate that the DENV-3 outbreak in the Caribbean region and Florida between 2022 and 2024 likely contributed to the introduction and spread of the virus throughout the country, the researchers assess.

“This demonstrates the need for molecular and genomic surveillance of circulating dengue serotypes for public health preparedness and response efforts for the emergence of cases of the disease”, highlights Lacerda.

Dengue transmission is widespread in tropical and subtropical regions around the world. However, risk areas have expanded in recent decades, mainly due to climate change and the expansion of the distribution of the transmitting mosquito, the Aedes aegypti point out the researchers.

Brazil is the most affected country in the Americas and has long been hyperendemic for all dengue virus serotypes. In recent years, DENV-1 and DENV-2 have been the most common serotypes in circulation. Although DENV-3 was detected during this period, it had a very low number of cases, with less than a hundred reported throughout the territory between 2010 and 2022. However, cases increased in 2023 (with 106 reported) and continued to increase in 2024 (with 1,008 cases).

“We have been studying dengue in Brazil since 2010 and the epidemiological pattern is similar to what happened with SARS-CoV-2 during the Covid-19 pandemic. When a different serotype appears, the population's previous immunity escapes and an epidemic soon follows. We are seeing this now with DENV-3”, says Lacerda.

This content was originally published in Resurgence of dengue serotype 3 could worsen outbreaks in Brazil on the CNN Brasil website.

Source: CNN Brasil