The underdiagnosed threat of oropouche fever amidst dengue epidemics in Brazil

Oropouche Fever (OF) is an emerging zoonotic arboviral disease caused by Oropouche Virus (OROV). Its transmission unfolds through two primary cycles: an urban cycle, predominantly facilitated by the Culicoides paraensis Goeldi mosquito bites in humans, and a more complex sylvatic cycle. This latter involves a diverse array of arthropod species, such as Aedes serratus, Culex quinquefasciatus, Coquillettidia venezuelensis, and other Culicoides, affecting numerous reservoir hosts including rodents, birds, and non-human primates.¹

The disease was first identified in Trinidad and Tobago during the 1950s, with OROV subsequently isolated in Brazil in 1960. Since then, OF has expanded its reach, primarily affecting the Amazon region and extending to countries across Central and South America, including Panama, Argentina, Bolivia, Ecuador, Peru, and Venezuela.² The geographic spread of the disease is often driven by environmental changes, such as deforestation, disorganized urbanization, and climate alterations, facilitating vector proliferation. Furthermore, human mobility significantly contributes to the dissemination of the virus, underscoring the intricate interplay between environmental and social factors in OF’s expansion.1, 2, 3

OF's incubation period ranges from 4 to 8 days, with clinical manifestations closely mimicking those of dengue and Chikungunya, including high fever, headache, arthralgia, myalgia, skin rashes, malaise, nausea, and vomiting. While most cases resolve within two weeks, severe complications, such as meningitis or encephalitis, may develop. The similarity of symptoms with other arboviruses poses a significant challenge for diagnosis, necessitating laboratory confirmation.⁴ Currently, treatment is primarily supportive, focusing on symptomatic relief, which underscores the importance of prevention and control strategies aimed at reducing vector mosquito populations and educating the public about transmission routes.1, 2, 3

The recent confirmation of OF’s first case in Rio de Janeiro on February 29, 2024, involving a 42-year-old man returning from Amazonas, signals the virus’s spread beyond traditional hotspots such as Amazonas, Acre, and Rondônia. Additionally, the record of 1674 OF cases in Amazonas in 2024, a threefold increase from the previous year, underscores the disease’s alarming escalation.⁵ The concurrent dengue epidemic, with over one million cases reported in Brazil during the first two months of 2024, combined with the symptomatic overlap between OF and other arboviruses and limited diagnostic capabilities, suggests a probable underdiagnosis of OF. This scenario presents a formidable challenge to the health system, necessitating heightened vigilance for accurate disease identification and control.

This situation demands a coordinated and proactive response from authorities, healthcare teams, researchers, and the international community. It is imperative to develop effective testing protocols, particularly in regions previously unacquainted with the disease. A detailed investigation of travel history, especially to the Amazon region, is vital for identifying and mitigating outbreaks, highlighting the urgency of informed prevention and control measures against the disease.

Contributors

All authors contributed equally to the manuscript.

Declaration of interests

The authors declare that there is no conflict of interest.