Credit: This image was released by the Agricultural Research Service, the research agency of the United States Department of Agriculture.
In early 2024, cases of Oropouche fever were reported in Amazonas, Brazil. Official data from Brazil indicated that from January to February, there were 1,674 confirmed cases of Oropouche virus infection in the state. By March 1, 2024, the Amazonas state government confirmed an outbreak of Oropouche fever. According to Science, by the end of May, Bolivia, Brazil, and Peru had all reported cases of this disease. This traditionally Amazon Basin-endemic disease is now infecting people outside the rainforest. Scientists and public health experts are concerned that this virus could become the next widespread epidemic in Latin America.
Over the past decade, Latin America has been battling diseases caused by the Zika and Chikungunya viruses. Currently, the region is experiencing one of the most severe dengue outbreaks in history, so even a minor epidemic could overwhelm the healthcare system.
What is Oropouche Fever?
Oropouche fever is a disease caused by the Oropouche virus, primarily transmitted through bites of midges. Most cases are mild, with symptoms including headaches, body aches, nausea, vomiting, and rashes. Severe cases can lead to brain inflammation and neurological issues, such as dizziness and drowsiness.
The Oropouche virus, an important arbovirus in the Peribunyaviridae family, was first discovered in French Guiana, South America, in 2020. To date, no fatalities have been reported. The virus can cause systemic infections, affecting the nervous and blood systems. It consists of three segments, with different segments encoding proteins that enable efficient replication and immune evasion in hosts. Phylogenetic analysis shows that the virus has distinct sequences geographically and shares closer homology with Iquitos and Perdões viruses of the Peribunyaviridae family. Despite its significant public health threat, there are no approved vaccines or specific antiviral treatments for the diseases caused by the Oropouche virus.
Why is Oropouche Fever Outbreaking in South America?
Oropouche fever is prevalent in South America, especially in the Amazon Basin. In forests, the virus circulates among primates, sloths, and birds, but the specific insect vector is unclear. In urban environments, tiny midges transmit the virus among humans. In recent years, the disease has started to spread beyond the Amazon Basin. The number of infections is likely underestimated due to the virus's similarity to dengue and Zika viruses, which require polymerase chain reaction or antibody tests for confirmation.
Researchers believe that increased human movement across the continent and between forests and cities has contributed to the expanded transmission range. They have also found a significant link between Oropouche fever outbreaks and deforestation. Deforestation may cause the virus to switch hosts from animals to humans as midges begin to feed on human blood instead of animal blood.
The most typical example is Manaus, the capital of Amazonas. The first cases of the current Oropouche fever outbreak were detected near deforested areas in Manaus. Studies using satellite imagery have confirmed this link. "In multiple locations in South America where the virus was detected, we also detected deforestation," said Daniel Romero-álvarez, an epidemiologist at SEK International University in Quito, Ecuador.
Additionally, climate change might play a role. High temperatures accelerate the growth of midges, while increased rainfall and flooding create breeding conditions for them.
Can Oropouche Fever be Controlled?
Brazil has intensified monitoring of Oropouche fever. Since January this year, samples from 10% of people nationwide with symptoms similar to Oropouche fever but negative for other viruses have been tested.
However, researchers note that controlling Oropouche fever is challenging. The disease and its vector have previously received little attention, and the tiny midges can easily bypass mosquito nets.
A model analysis by Romero-álvarez in 2023, which considered current climate change and vegetation loss, suggested that 5 million people in the Americas are at risk of Oropouche fever. This figure might be underestimated, as the model did not predict the disease's spread to other major cities or account for future deforestation and climate change trends. Additionally, the model did not consider the possibility that tropical house mosquitoes or other insects might also transmit the virus.
Moreover, scientists worry that as the virus spreads, its genes might mutate, making it more dangerous. Unlike most arbovirus genomes, which consist of a single RNA segment, Oropouche fever has three. When two different strains infect the same cell, they can exchange segments, creating new, distinct genetic combinations that can evade the host's immune response.
Therefore, researchers call for expanded testing and more researchers to study the Oropouche virus and track its genomic changes. Meanwhile, cases have been detected in Brazil, Cuba, and Bolivia, but no direct human-to-human transmission has been observed. For safety, avoid traveling to affected areas and maintain a clean living environment.
Reference：
Yuli Zhang, Xiao Liu, Zhen Wu, Shuo Feng, Ke Lu, Wenbing Zhu, Hengyi Sun, Guoyu Niu,Oropouche virus: A neglected global arboviral threat,Virus Research,Volume 341,2024,199318,ISSN 0168-1702,https://doi.org/10.1016/j.virusres.2024.199318.
https://www.science.org/content/article/little-known-virus-rise-south-america-could-overwhelm-health-systems
https://www.cubaheadlines.com/articles/282621
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