Research led by the Oswaldo Cruz Foundation (Fiocruz) pointed out that the recent outbreak of Oropouche fever in the Amazon region, the largest ever recorded, was caused by a new viral lineage, called 'OROV BR-2015-2024'.
The peer-reviewed article was published in the prestigious international scientific journal Nature Medicine in an accelerated manner to allow early access to the findings. The final edited version of the paper will be published soon in the journal.
Previously, as a way of communicating the research results to the scientific community, the study was published in a preliminary version on the preprint platform medRxiv, which does not have a peer review process.
The research analyzed samples relating to 382 cases registered between August 2022 and February 2024 in the states of Amazonas, Acre, Rondônia and Roraima.
During the period, more than six thousand cases were recorded in 140 municipalities in the North Region.
The analyses revealed that the infections were caused by a new strain of the Oropouche virus, which was also detected in a sample collected in the city of Tefé, in Amazonas, in 2015, and in French Guiana, in 2020.
Considering the genetic characteristics of the pathogen, researchers assess that the 'OROV BR-2015-2024' lineage probably emerged between 2010 and 2014 in the state of Amazonas, spreading silently until causing the recent epidemic.
Art: Jefferson Mendes
F Unit Researchersiocruz in five states collaborated in the research: Oswaldo Cruz Institute (IOC/Fiocruz), in Rio de Janeiro; Leonidas and Maria Deane Institute (Fiocruz-Amazonia), in the Amazon; Fiocruz-Rondônia; Aggeu Magalhães Institute (Fiocruz-Pernambuco) and Carlos Chagas Institute (Fiocruz-Paraná).
The work also had the cooperation of the Central Public Health Laboratories (Lacens) of Amazonas, Acre, Rondônia, Roraima and Paraná; State Health Secretariat of Acre (Sesacre); General Coordination of Public Health Laboratories (CGLab) and General Coordination of Arbovirus Surveillance (CGArb) of the Ministry of Health; Evandro Chagas Institute (IEC), Federal Universities of Amazonas (Ufam), Espírito Santo (Ufes) and Pernambuco (UFPE); Amazonas State University (UEA); Global Data Science Initiative platform (Gisaid); in addition to the Universities of California and Cornell, in the United States.
Research leader, virologist Felipe Naveca explains that the new lineage of the Oropouche virus emerged through genetic rearrangement between strains that circulated in Brazil and another circulating in Peru, Colombia and Ecuador.
“The new lineage emerged from an evolutionary event that we call genetic reassortment. This occurs when the same person or animal is infected by two different viral lineages simultaneously. Thus, in the process of viral replication, a strain can emerge that is a combination of two pathogens, as we observed in this case,” explains Naveca, who is head of the Laboratory of Arboviruses and Hemorrhagic Viruses at the IOC and coordinator of the Surveillance Center for Emerging, Reemerging or Neglected Viruses of the Fioccross Amazon.
According to scientists, further research is still needed to determine the impact of the emergence of the new lineage on the spread of Oropouche fever in the Amazon and beyond.
On the one hand, the new strain presents changes in the surface of the viral particle that may facilitate the escape of antibodies. Thus, people previously infected with the Oropouche virus may have reduced protection against the new lineage.
In addition, a preliminary study, carried out by another group of scientists and not yet peer-reviewed, indicates that the new strain replicates more quickly in cells than the first lineage of the Oropouche virus isolated in Brazil in the 1960s.
On the other hand, researchers note that the new lineage circulated for almost ten years until causing a large-scale outbreak.
In this context, scientists draw attention to the impact of extreme weather events and environmental degradation on the transmission of Oropouche fever.
“An epidemic situation is usually multifactorial. There is a new strain that has successfully spread. However, this cannot be attributed solely to one virtue of the virus. We have a context of climate change and deforestation, which affect the behavior of the vector and which, most likely, contributed to the population’s greater exposure to the virus,” emphasizes Naveca.
The article published in Nature Medicine highlights that the recent Oropouche outbreak, between 2022 and 2024, was preceded by record flooding in the Amazon associated with the La Niña meteorological phenomenon, which, unusually, extended from 2020 to 2023. Subsequently, the region suffered from record drought and heat during the transition to the El Niño phenomenon.
The increase in deforestation in the Amazon since 2018 may also have contributed to the spread of the disease. The highest incidence of Oropouche fever was observed in the region called Amacro, which includes municipalities in Amazonas, Acre and Rondônia, where much of the forest loss occurred between 2017 and 2021. In Roraima, municipalities close to the most critical areas of deforestation also concentrated infections.
The study confirmed the seasonal pattern of Oropouche fever. According to the scientists, high transmission of the virus was observed in the rainy seasons and low, although persistent, transmission in the dry seasons.
This pattern can be explained by the greater proliferation of the disease vector during the rainy season, since the insect Culicoides paraensis, popularly known as maruim or gunpowder mosquito, reproduces in environments with moist organic matter.
By analyzing the genetic characteristics of the viruses and the locations where cases were recorded, researchers observed that the spread of the disease occurred through a combination of movements of vectors and infected humans.
In about two-thirds of cases, virus dispersal was consistent with the insects' flight range, remaining below 2 km per day. However, in approximately one-third of cases, a dispersal of more than 10 km per day was observed, indicating an association with human movement.
The sequencing of a large number of complete genomes was one of the research's strengths. The amount of 382 sequences decoded in the study is five times greater than the total that was previously available in databases, which accounted for around 70 deposited genomes.
The protocol for genetic sequencing of the Oropouche virus, developed by scientists, can facilitate the work of genomic surveillance of the pathogen in Brazil and other countries.
The importance of monitoring the condition is highlighted by scientists, recalling that, only last year, the country began to systematically diagnose cases of Oropouche.
Developed by Fiocruz Amazônia, a protocol for detecting the Oropouche and Mayaro viruses was implemented in all Lacens by the Ministry of Health.
“We need to remain vigilant to understand the country’s epidemiological situation. In a year with more than six million cases of dengue, around eight thousand cases of Oropouche fever would go unnoticed if there were no laboratory diagnosis, because the symptoms of the two diseases are very similar,” says Naveca.
“We are living in a context of climate change and deforestation that alters ecological niches and changes the behavior of vectors and other animals. It is essential to be alert to detect emerging diseases, such as Oropouche,” adds the virologist.
Article: Naveca, FG et al. Human outbreaks of a novel reassortant Oropouche virus in the Brazilian Amazon region. Nature Medicine, 2024. Available at: https://doi.org/10.1038/s41591-024-03300-3
Research led by the Oswaldo Cruz Foundation (Fiocruz) pointed out that the recent outbreak of Oropouche fever in the Amazon region, the largest ever recorded, was caused by a new viral lineage, called 'OROV BR-2015-2024'.
The peer-reviewed article was published in the prestigious international scientific journal Nature Medicine in an accelerated manner to allow early access to the findings. The final edited version of the paper will be published soon in the journal.
Previously, as a way of communicating the research results to the scientific community, the study was published in a preliminary version on the preprint platform medRxiv, which does not have a peer review process.
The research analyzed samples relating to 382 cases registered between August 2022 and February 2024 in the states of Amazonas, Acre, Rondônia and Roraima.
During the period, more than six thousand cases were recorded in 140 municipalities in the North Region.
The analyses revealed that the infections were caused by a new strain of the Oropouche virus, which was also detected in a sample collected in the city of Tefé, in Amazonas, in 2015, and in French Guiana, in 2020.
Considering the genetic characteristics of the pathogen, researchers assess that the 'OROV BR-2015-2024' lineage probably emerged between 2010 and 2014 in the state of Amazonas, spreading silently until causing the recent epidemic.
Art: Jefferson Mendes
F Unit Researchersiocruz in five states collaborated in the research: Oswaldo Cruz Institute (IOC/Fiocruz), in Rio de Janeiro; Leonidas and Maria Deane Institute (Fiocruz-Amazonia), in the Amazon; Fiocruz-Rondônia; Aggeu Magalhães Institute (Fiocruz-Pernambuco) and Carlos Chagas Institute (Fiocruz-Paraná).
The work also had the cooperation of the Central Public Health Laboratories (Lacens) of Amazonas, Acre, Rondônia, Roraima and Paraná; State Health Secretariat of Acre (Sesacre); General Coordination of Public Health Laboratories (CGLab) and General Coordination of Arbovirus Surveillance (CGArb) of the Ministry of Health; Evandro Chagas Institute (IEC), Federal Universities of Amazonas (Ufam), Espírito Santo (Ufes) and Pernambuco (UFPE); Amazonas State University (UEA); Global Data Science Initiative platform (Gisaid); in addition to the Universities of California and Cornell, in the United States.
Research leader, virologist Felipe Naveca explains that the new lineage of the Oropouche virus emerged through genetic rearrangement between strains that circulated in Brazil and another circulating in Peru, Colombia and Ecuador.
“The new lineage emerged from an evolutionary event that we call genetic reassortment. This occurs when the same person or animal is infected by two different viral lineages simultaneously. Thus, in the process of viral replication, a strain can emerge that is a combination of two pathogens, as we observed in this case,” explains Naveca, who is head of the Laboratory of Arboviruses and Hemorrhagic Viruses at the IOC and coordinator of the Surveillance Center for Emerging, Reemerging or Neglected Viruses of the Fioccross Amazon.
According to scientists, further research is still needed to determine the impact of the emergence of the new lineage on the spread of Oropouche fever in the Amazon and beyond.
On the one hand, the new strain presents changes in the surface of the viral particle that may facilitate the escape of antibodies. Thus, people previously infected with the Oropouche virus may have reduced protection against the new lineage.
In addition, a preliminary study, carried out by another group of scientists and not yet peer-reviewed, indicates that the new strain replicates more quickly in cells than the first lineage of the Oropouche virus isolated in Brazil in the 1960s.
On the other hand, researchers note that the new lineage circulated for almost ten years until causing a large-scale outbreak.
In this context, scientists draw attention to the impact of extreme weather events and environmental degradation on the transmission of Oropouche fever.
“An epidemic situation is usually multifactorial. There is a new strain that has successfully spread. However, this cannot be attributed solely to one virtue of the virus. We have a context of climate change and deforestation, which affect the behavior of the vector and which, most likely, contributed to the population’s greater exposure to the virus,” emphasizes Naveca.
The article published in Nature Medicine highlights that the recent Oropouche outbreak, between 2022 and 2024, was preceded by record flooding in the Amazon associated with the La Niña meteorological phenomenon, which, unusually, extended from 2020 to 2023. Subsequently, the region suffered from record drought and heat during the transition to the El Niño phenomenon.
The increase in deforestation in the Amazon since 2018 may also have contributed to the spread of the disease. The highest incidence of Oropouche fever was observed in the region called Amacro, which includes municipalities in Amazonas, Acre and Rondônia, where much of the forest loss occurred between 2017 and 2021. In Roraima, municipalities close to the most critical areas of deforestation also concentrated infections.
The study confirmed the seasonal pattern of Oropouche fever. According to the scientists, high transmission of the virus was observed in the rainy seasons and low, although persistent, transmission in the dry seasons.
This pattern can be explained by the greater proliferation of the disease vector during the rainy season, since the insect Culicoides paraensis, popularly known as maruim or gunpowder mosquito, reproduces in environments with moist organic matter.
By analyzing the genetic characteristics of the viruses and the locations where cases were recorded, researchers observed that the spread of the disease occurred through a combination of movements of vectors and infected humans.
In about two-thirds of cases, virus dispersal was consistent with the insects' flight range, remaining below 2 km per day. However, in approximately one-third of cases, a dispersal of more than 10 km per day was observed, indicating an association with human movement.
The sequencing of a large number of complete genomes was one of the research's strengths. The amount of 382 sequences decoded in the study is five times greater than the total that was previously available in databases, which accounted for around 70 deposited genomes.
The protocol for genetic sequencing of the Oropouche virus, developed by scientists, can facilitate the work of genomic surveillance of the pathogen in Brazil and other countries.
The importance of monitoring the condition is highlighted by scientists, recalling that, only last year, the country began to systematically diagnose cases of Oropouche.
Developed by Fiocruz Amazônia, a protocol for detecting the Oropouche and Mayaro viruses was implemented in all Lacens by the Ministry of Health.
“We need to remain vigilant to understand the country’s epidemiological situation. In a year with more than six million cases of dengue, around eight thousand cases of Oropouche fever would go unnoticed if there were no laboratory diagnosis, because the symptoms of the two diseases are very similar,” says Naveca.
“We are living in a context of climate change and deforestation that alters ecological niches and changes the behavior of vectors and other animals. It is essential to be alert to detect emerging diseases, such as Oropouche,” adds the virologist.
Article: Naveca, FG et al. Human outbreaks of a novel reassortant Oropouche virus in the Brazilian Amazon region. Nature Medicine, 2024. Available at: https://doi.org/10.1038/s41591-024-03300-3
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