An article published in the journal Emerging Infectious Diseases reveals that Mayaro and chikungunya viruses are co-circulating in Roraima, Brazil’s northernmost state within the Amazon biome. The authors emphasize the urgent need for more effective epidemiological surveillance in the region.
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Chikungunya Viruses
The researchers were initially surprised by their discovery. They had hypothesized that other viruses were unlikely to circulate in areas with high infection rates of either Mayaro or chikungunya, according to José Luiz Proença-Modena, a professor at the State University of Campinas’s Institute of Biology (IB-UNICAMP) in Brazil and the study’s senior author.
“Antigen sharing between Mayaro and chikungunya was expected to provide cross-protection,” Proença-Modena explained. “Specific antibodies and T lymphocytes produced in response to one virus were believed to recognize the other. Contrary to this belief, we detected both viruses in the same areas.” Notably, no cases of simultaneous infection by both viruses were observed.
The authors suggest that the co-circulation of these arboviruses necessitates enhanced molecular and genomic surveillance, as well as improved diagnostic methods such as RT-PCR to detect genetic material in biological samples.
Julia Forato, a corresponding author of the article, noted that the clinical symptoms of these viruses—such as fever, joint pain, and fatigue—are similar, making them difficult to distinguish. The Mayaro virus is transmitted by the Haemagogus janthinomys mosquito, which also spreads yellow fever. Deforestation due to illegal mining and other human activities could facilitate its transmission in urban areas.
Individuals working in the forest, such as miners, loggers, and fishermen, may introduce the virus to urban areas, Forato explained. In the study, 11% of samples infected by the Mayaro virus were from fishermen.
“Improved and expanded molecular and genomic surveillance, encompassing both vector mosquitoes and the human population, is crucial,” Proença-Modena said. “Robust surveillance will help detect human-amplified transmission cycles, understand how human activities in forest areas impact virus circulation dynamics, and predict potential new outbreaks. These diseases cause significant financial and social harm to patients and impose a heavy burden on the health system.”
The study is part of a larger project, Amazon+10, aiming to understand how human activities affect viral circulation dynamics in forest areas. This project focuses on regions like the Manaus-Porto Velho highway, a mining area in Pará state, and parts of Roraima state with numerous migrants and illegal mining operations.
Researchers from various institutions, including UNICAMP, the Federal University of Roraima (UFRR), Roraima’s Central Public Health Laboratory, the University of São Paulo (USP), Fiocruz Amazonia, Imperial College London, and the University of Kentucky, are involved in this research under the Amazon+10 initiative. The goal is to promote nature-society interaction and sustainable development in Legal Amazonia, an area encompassing over 5 million km² across nine Brazilian states.
“This was the first study for the project, aiming to identify viruses circulating in Roraima,” Proença-Modena said. “We analyzed samples collected between December 2018 and December 2021 during dengue and chikungunya outbreaks, mapping viral circulation in the region.”
Blood samples were collected from 822 health clinic patients with acute febrile illness. Of these, 190 (23.1%) tested positive for more than one arbovirus. Real-time reverse-transcriptase polymerase-chain-reaction (rRT-PCR) testing detected dengue in 146 (17.8%), Mayaro in 28 (3.4%), and chikungunya in 16 (2%). All samples tested negative for zika, Oropouche, and dengue serotypes 3 and 4.
“In addition to detecting co-circulation of Mayaro and chikungunya, we found a high frequency of dengue, including co-infections with dengue 1 and 2. The virus causing the infection couldn’t be precisely identified in most cases (76.9%), suggesting a novel pathogen or combination is likely circulating,” Proença-Modena said.
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