Resurgence of dengue serotype 3 worries experts

The recent resurgence of serotype 3 of the dengue virus in Brazil – which has not caused epidemics in the country for over 15 years – has raised the alarm about the risk of a new epidemic of the disease caused by this virus serotype. A study by Fiocruz, coordinated by Fiocruz Amazônia and the Oswaldo Cruz Institute (IOC/Fiocruz), presents the genetic characterization of the viruses referring to four cases of the infection recorded this year, in Roraima, in the North Region, and in Paraná, in the South of the country. The circulation of a long-absent serotype worries specialists.

"In this study, we conducted the genetic characterization of cases of infection by serotype 3 of the dengue virus. It is an indication that we may once again have, perhaps not now, but in the coming months or years, epidemics caused by this serotype", explains the virologist Felipe Naveca, head of the Center for Surveillance of Emerging, Reemerging and Neglected Viruses at Fiocruz Amazônia and researcher at the Arbovirus and Hemorrhagic Virus Laboratory of Oswaldo Cruz Institute/Fiocruz, which acts as a regional reference for dengue, yellow fever, chikungunya, zika and West Nile virus. With the aim of quickly sharing information, the results of the analysis were published in a preprint article on the medRxiv platform, without the peer review process. The work was submitted for publication in a scientific journal. The research was carried out in partnership with the Central Public Health Laboratories (Lacens) in Roraima and Paraná and had the participation of specialists from various research institutions.

According to Naveca, the analyses indicate that the strain detected was introduced in the Americas from Asia, in the period between 2018 and 2020, probably in the Caribbean. "The serotype 3 strain that we have detected is not the same that circulated in the Americas, which caused epidemics in Brazil in the early 2000s. Our results showed that there was a new introduction of genotype III of serotype 3 of the dengue virus in the Americas from Asia. This strain is circulating in Central America and has also recently infected people in the United States. Now, we have identified that it has arrived in Brazil", reports Naveca.

Of the four cases analyzed, three refer to indigenous cases in Roraima, that is, they correspond to patients who were infected in the state and had no travel history. The case in Paraná was imported, diagnosed in a person coming from Suriname.

The cases were initially identified by the Lacens (Central Laboratories of Public Health) of Roraima and Paraná, respectively. "Since this refers to serotype 3, it was important for us to carry out this analysis together with the Lacens and several other research institutions that sign this result, including the Evandro Chagas Institute in Pará, a national reference for arboviruses, the Center for Disease Control and Prevention of the United States (CDC) – Puerto Rico unit, and the State Department of Health of Florida. It was the teams from the CDC in Puerto Rico and the Department of Health of Florida that identified the cases coming from Cuba and the USA. Thus, this is a valid alert not only for Brazil, but for the entire region of the Americas. Bearing in mind that we are experiencing a large number of cases of arboviruses this year in Brazil, the detection of a new serotype of the dengue virus is not good news", he warned.

The dengue virus has four serotypes. Infection by one of them generates immunity against the same serotype, but it is possible to contract dengue again if there is contact with a different serotype. The risk of an epidemic with the return of serotype 3 occurs because of the low immunity of the population, since few people have contracted this virus since the last epidemics recorded in the early 2000s. There is also the danger of severe dengue, which occurs more frequently in people who have already had the disease and are infected again by another serotype.

The research was sponsored by the Research Support Foundation of the State of Amazonas (Fapeam); the Genomic Health Surveillance Network of Amazonas; the Fiocruz Genomic Network; Inova Fiocruz (Inovação Amazônia); the Science and Technology Department (Decit) of the Brazilian Ministry of Health; the National Council for Scientific and Technological Development (CNPq); and the Research Support Foundation of the State of Rio de Janeiro (Faperj).