MAYARO AND CHIKUNGUNYA VIRUSES – BRAZIL: (RORAIMA) CO-CIRCULATION
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Date: Thu 11 Jul 2024 00:50 AEST
Source: Mirage News [abridged, edited]
https://www.miragenews.com/mayaro-chikungunya-viruses-found-simultaneously-1272812/
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 (https://doi.org/10.3201/eid3005.231406). 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.
“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 2 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 former awardee of a scholarship
from FAPESP and 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 insisted.
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.
“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.