Researchers observe Mayaro and chikungunya viruses circulating at the same time in the Brazilian Amazon

An article published in the journal Emerging Infectious Diseases shows that Mayaro and chikungunya viruses are circulating at the same time (co-circulating) in Roraima, Brazil’s northernmost state and part of the Amazon biome. According to the authors, their findings reinforce the need for more effective epidemiological surveillance in the region.

The researchers were surprised by the discovery. Their initial hypothesis was that other viruses were highly unlikely to circulate in places where the rate of infection by either Mayaro or chikungunya was already high, José Luiz Proença-Modena, a professor at the State University of Campinas’s Institute of Biology (IB-UNICAMP) in Brazil and last author of the article, told Agência FAPESP.

Proença-Modena said, “Antigen sharing by Mayaro and chikungunya is significant, and so infection by one was expected to afford protection against the other. The belief was that specific antibodies and T lymphocytes [cells of the immune system] produced in response to infection by one virus would be able to recognize the other. On the contrary, however, we detected both Mayaro and chikungunya in the same areas.”

He added that no cases of individuals infected simultaneously by both viruses were observed.

According to the authors, co-circulation of these two arboviruses points to the need for augmented molecular and genomic surveillance, and for a more refined diagnostic methodology using tests like RT-PCR to detect the genetic material present in biological samples.

“The diseases caused by these viruses are hard to distinguish clinically. Their symptoms are similar, including fever, joint pain and fatigue,” said Julia Forato, a corresponding author of the article.

She explained that Mayaro virus is transmitted by Haemagogus janthinomys, a sylvatic mosquito that also transmits yellow fever. Deforestation due to illegal mining (garimpos) and other human activities could favor transmission in urban areas.

People who work in the forest (in mining, logging and fishing, for example) can act as a bridge, she said, introducing the virus to urban areas and enabling transmission there. In the study, 11% of the samples infected by Mayaro virus were from fishermen.

“Improved and expanded molecular and genomic surveillance, encompassing the mosquitoes that act as vectors as well as the human population, would help us detect a human-amplified transmission cycle. We need robust surveillance, not only to find out how much the virus’s circulation dynamics may be affected by human activities in forest areas but also to predict possible new outbreaks. All these diseases are highly incapacitating. They cause financial and social harm to patients, and incur a heavy burden for the health system to provide treatment,” Proença-Modena said.

Amazon+10

The study reported in the article was part of an endeavor to see how human activities affect the dynamics of viral circulation in forest areas, focusing on the Manaus-Porto Velho highway (BR-319), currently undergoing renovation; a mining area in Pará state; and this part of Roraima state, where there are many migrants and garimpos near urban settlements.

Besides UNICAMP, the venture involves researchers at the Federal University of Roraima (UFRR); Roraima’s Central Public Health Laboratory; the University of São Paulo (USP); Fiocruz Amazonia, the Manaus unit of Oswaldo Cruz Foundation (an arm of the Ministry of Health that conducts research and development in biological sciences); Imperial College London in the United Kingdom; and the University of Kentucky in the United States.

All this research is being conducted under the umbrella of Amazon+10. The goal is to foster nature-society interaction and sustainable inclusive development in Legal Amazonia, an area of more than 5 million km² comprising nine Brazilian states where the biome occurs, created by federal law to promote environmental protection and regional development.

“This was the first study conducted for the project. We set out to see which viruses were circulating in Roraima. We analyzed samples collected between December 2018 and December 2021, during outbreaks of dengue and chikungunya. The analysis enabled us to map viral circulation in the region,” Proença-Modena said.

Blood samples were donated by 822 health clinic patients with acute febrile illness (high fever, chills, muscle pain and cough). Of these, 190 (23.1%) tested positive for more than one arbovirus. Arborviruses are transmitted by invertebrate animals, especially mosquitoes.

Real-time reverse-transcriptase polymerase-chain-reaction (rRT-PCR) testing of RNA extracted from the blood samples 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 very high frequency of dengue [including co-infection by dengue 1 and 2]. We also noted that the virus causing the infection couldn’t be precisely identified in most cases [76.9%]. This means a novel pathogen or combination is probably circulating,” Proença-Modena said.