The Oswaldo Cruz Foundation (F.iocruz) and Central Public Health Laboratories (Lacens) in the Midwest concluded new sequencing of the dengue virus. The genomic surveillance work in the region was intensified after the unprecedented identification of the cosmopolitan genotype of serotype 2 of the pathogen in Brazil, carried out in May, in Goiás.

The new analyzes detected the lineage in another 14 samples, from Goiás (7), Mato Grosso do Sul (4) and Mato Grosso (3), bringing the total number of records in the region to 15.

Genetic sequencing was carried out by the Flavivirus Laboratory of Instituto Oswaldo Cruz (IOC/Fiocruz) in partnership with the Lacens of the three states. Reports referring to the work were sent to the State Health Secretariats, the Ministry of Health and the Pan American Health Organization (PAHO).

The cosmopolitan genotype is the most widespread strain of dengue virus serotype 2 worldwide, with a presence in Asia, the Pacific, the Middle East and Africa. In the Americas, the first identification occurred in 2019, during an outbreak in Peru. In Brazil, in addition to notifications in the Midwest, six cases were detected in analyzes carried out by the Adolfo Lutz Institute, in São Paulo, last month.
 

The researcher from the Flavivirus Laboratory of the IOC, Luiz Alcântara, who coordinated the study in the Midwest, says that the new data confirm the sustained circulation of the lineage in the region. “Considering the increase in the number of cases from February until today, we see that the cosmopolitan genotype of serotype 2 of the dengue virus is being actively transmitted”, says the virologist.

Of the 15 findings, two occurred in samples referring to cases from 2021: one registered in July, in Mato Grosso do Sul, and another, in November, in Goiás (this being the first case detected in the country, during a genomic surveillance action carried out in May in the state). The remaining identifications were carried out in samples referring to cases that occurred from February 2022. In two cases, registered in Goiás, the cosmopolitan lineage was detected in samples referring to cases of death due to dengue.

According to Alcântara, the findings reinforce the importance of surveillance actions to map the spread of the lineage in Brazil. “It is necessary to carry out surveillance in all states of the country”, he points out.

virus routes

The increase in the number of genetic sequencing in the Midwest allowed us to point out that the introduction of the cosmopolitan lineage in Brazil originated from Peru. Furthermore, although the genotype was detected first in Goiás, viral circulation occurred earlier in Mato Grosso and Mato Grosso do Sul. “In our evolutionary analysis, we see that the virus left Peru and entered Mato Grosso and Mato Grosso do Sul and, later, went to Goiás”, says Alcântara.

According to the researcher, the sequencing of more samples will be necessary to clarify in which state the pathogen first circulated and whether it passed through other countries before arriving in Brazil. One of the suspects is that the virus may have arrived in Mato Grosso through the border with Paraguay, given that the country has been registering high numbers of dengue cases.

“To respond to this, we are working in partnership with the Central Public Health Laboratory of Paraguay. In July, they should come to the Flavivirus Laboratory of IOC, in Rio de Janeiro, where we will carry out the sequencing of samples collected in the country”, anticipates Alcântara.

Also in the first half of this year, scientists should carry out genetic sequencing in partnership with Lacen do Paraná. In addition to the border with Paraguay, the state borders Mato Grosso do Sul and São Paulo, two states where the cosmopolitan genotype was detected.

Most widespread genotype

The cosmopolitan genotype of dengue virus serotype 2 is the most widespread and has the greatest impact in the world. However, there is not enough data to confirm that the lineage is more transmissible or can lead to more severe cases than others.

In this scenario, the researchers plan another stage of research, with the objective of investigating, in the laboratory, the characteristics of the infection caused by the strain. “We are isolating the viruses and we are going to carry out experiments to evaluate, in an experimental model, whether there is an increase in the severity of the disease or not”, clarifies the virologist.

The researcher adds that, by itself, the increased diversity of dengue viruses circulating in the country may increase the risk of severe cases of the disease.

“Cases of severe dengue, which can lead to death, are closely related to reinfection with different serotypes. As we have one more genotype in circulation, the population of a given serotype grows. This increases the possibility of cases of reinfection and, consequently, of severe cases of dengue”, he explains.

The researcher also reinforces that combating the Aedes aegypti mosquito, the vector of the disease, is the main way to contain the spread of the virus, regardless of the serotypes or strains in circulation.

“It is very important for the population to know that there is another genotype of the dengue virus in the country and that the vector control measures must continue. Even with winter approaching, it is necessary to avoid the accumulation of stagnant water in homes, which has always been recommended by the Ministry of Health”, says Alcântara, remembering that, despite the low temperatures reducing the proliferation of the vector, the weekly verification of the breeders needs to continue.

genomic surveillance project

To investigate the circulation of the cosmopolitan lineage in the Midwest, the researchers carried out the genetic sequencing of all samples stored in the region's Lacens referring to cases of infection with serotype 2 of the dengue virus registered since 2019. In all, it was possible to decode 100 genomes of the pathogen, 87 from Goiás, 10 from Mato Grosso do Sul and three from Mato Grosso.

All 72 samples from 2019 and 2020 were identified as belonging to the Asian American genotype (also called genotype III of serotype 2), which has been circulating in Brazil for years. Among the 15 analyzed 2021 samples, two presented the cosmopolitan genotype. As early as 2022, among 16 decoded samples, 13 belonged to this lineage.

“These samples represent only a part of the cases of dengue registered in these states, as it is not always possible to collect samples in the volume necessary for genetic sequencing”, clarifies Alcântara.

The unprecedented identification of the cosmopolitan genotype of the dengue virus in Brazil and the new genetic sequencing were carried out from a real-time arbovirus genomic surveillance project, led by Luiz Alcântara, researcher at the Flavivirus Laboratory of the IOC. In the initiative, the researchers travel to the states to carry out the decoding of genomes.

Since 2020, the work has also included the genomic surveillance of SARS-CoV-2, which causes Covid-19, under the name of UWARN (United Word Antiviral Research Network). The project is in collaboration with the Ministry of Health, through the General Coordination Office for Arboviruses (CGArb) and Public Health Laboratories (CGLab), and the Pan American Health Organization (PAHO), and is funded by the National Institutes of Health (NIH, in acronym in English), from the United States.