Oropouche virus infection in patients with acute febrile syndrome: Is a predictive model based solely on signs and symptoms useful?

Mysterious Oropouche virus: Transmission, symptoms, and control

The Oropouche virus (OROV) is a new zoonotic arbovirus that mostly affects Brazil and nearby countries. Since its discovery in 1955, it has caused more than 500,000 infections, with symptoms ranging from fever and headache to serious neuroinvasive disorders such as meningitis and encephalitis. The virus spreads through urban and sylvatic cycles via vectors such as Culicoides midges and Culex mosquitos, with humans and some vertebrates serving as amplifying hosts. The manuscript aims to analyze the transmission dynamics, clinical manifestations, diagnostic approaches, and potential preventive strategies for OROV. OROV is becoming an increasing health concern due to its global expansion and potential for serious consequences. Its growing threat, especially in light of the possibility of congenital abnormalities, is highlighted by the first recorded deaths in 2024 and the verification of vertical transmission. Clinical symptoms overlap greatly with other arboviruses, limiting early diagnosis; nonetheless, molecular approaches such as RT-PCR are crucial for identification. The current therapy is restricted to symptom control, highlighting the critical need for effective vaccinations. Live attenuated vaccination candidates and innovative techniques based on reverse genetics systems are both promising discoveries. However, the genetic variety of OROV strains poses obstacles to obtaining broad protection. To combat OROV, improved surveillance, strong public health initiatives, and quick vaccine development are needed. Public education and sustainable vector control are also essential for controlling outbreaks and lessening the virus effects.

Global infectious disease early warning models: An updated review and lessons from the COVID-19 pandemic

An early warning model for infectious diseases is a crucial tool for timely monitoring, prevention, and control of disease outbreaks. The integration of diverse multi-source data using big data and artificial intelligence techniques has emerged as a key approach in advancing these early warning models. This paper presents a comprehensive review of widely utilized early warning models for infectious diseases around the globe. Unlike previous review studies, this review encompasses newly developed approaches such as the combined model and Hawkes model after the COVID-19 pandemic, providing a thorough evaluation of their current application status and development prospects for the first time. These models not only rely on conventional surveillance data but also incorporate information from various sources. We aim to provide valuable insights for enhancing global infectious disease surveillance and early warning systems, as well as informing future research in this field, by summarizing the underlying modeling concepts, algorithms, and application scenarios of each model.

Potential therapeutics and vaccines: Current progress and challenges in developing antiviral treatments or vaccines for Oropouche virus

Oropouche virus (OROV), an emerging arbovirus, poses a significant public health challenge in tropical and subtropical regions, with no licensed vaccines or antiviral therapies currently available. This review explores recent advancements in therapeutic strategies and vaccine development for OROV, focusing on molecular mechanisms of viral replication, identification of potential antiviral targets, and the role of immunotherapy in managing infections. Promising antiviral candidates, including ribavirin, mycophenolic acid, and interferon, have demonstrated efficacy in in vitro studies, offering a foundation for further investigation. The challenges of preclinical and clinical development, such as high mutation rates, immune response variability, and vaccine delivery hurdles, are critically analyzed. By addressing the progress and remaining gaps, this article aims to provide a comprehensive overview to inform future research and facilitate the development of effective antiviral strategies and vaccines for OROV.

Addressing the emerging threat of Oropouche virus: implications and public health responses for healthcare systems

Oropouche fever is an increasingly significant health concern in tropical and subtropical areas of South and Central America, and is primarily spread by midge vectors. The Oropouche virus (OROV) was first identified in 1955 and has been responsible for numerous outbreaks, particularly in urban environments. Despite its prevalence, the disease is often under-reported, making it difficult to fully understand its impact. OROV typically causes febrile illness characterized by symptoms such as headaches, muscle pain, and, occasionally, neurological issues such as meningitis. The ability of the virus to thrive in both forested and urban areas has raised concerns regarding its potential spread to new regions, particularly in the context of climate change. This paper delves into the epidemiology, clinical features, and transmission patterns of OROV, shedding light on the difficulties in diagnosing and managing the disease. The absence of specific treatments and vaccines highlights the urgent need for continued research and development of targeted public health strategies. Advancements in molecular diagnostics and vector control strategies can mitigate Oropouche fever's impact. However, a comprehensive public health approach involving increased surveillance, public education, and cross-border collaboration is needed, especially as the global climate crisis may expand vector habitats, posing risks to previously unaffected regions.

Human outbreaks of a novel reassortant Oropouche virus in the Brazilian Amazon region

The Brazilian western Amazon is experiencing its largest laboratory-confirmed Oropouche virus (OROV) outbreak, with more than 6,300 reported cases between 2022 and 2024. In this study, we sequenced and analyzed 382 OROV genomes from human samples collected in Amazonas, Acre, Rondônia and Roraima states, between August 2022 and February 2024, to uncover the origin and genetic evolution of OROV in the current outbreak. Genomic analyses revealed that the upsurge of OROV cases in the Brazilian Amazon coincides with spread of a novel reassortant lineage containing the M segment of viruses detected in the eastern Amazon region (2009-2018) and the L and S segments of viruses detected in Peru, Colombia and Ecuador (2008-2021). The novel reassortant likely emerged in the Amazonas state between 2010 and 2014 and spread through long-range dispersion events during the second half of the 2010s. Phylodynamics reconstructions showed that the current OROV spread was driven mainly by short-range (< 2 km) movements consistent with the flight range of vectors. Nevertheless, a substantial proportion (22%) of long-range (>10 km) OROV migrations were also detected, consistent with viral dispersion by humans. Our data provide a view of the unprecedented spread and evolution of OROV in the Brazilian western Amazon region.

Oropouche Virus: An Emerging Neuroinvasive Arbovirus

Oropouche virus (OROV) is an arthropod-borne virus (arbovirus) in the Orthobunyavirus genus and Peribunyaviridae viral family that is endemic to parts of South America, Central America, and the Caribbean. It has recently emerged in Cuba, and travel-imported cases are recently being reported in the United States and Europe. Typically maintained in a sylvatic cycle between certain forest sloths, non-human primates, birds, and mosquitoes, OROV disease outbreaks can occur in an urban cycle between certain biting midges and/or mosquitoes and humans. Clinically, approximately 60% of infections are symptomatic with an abrupt fever and non-specific influenza-like illness within 3 to 10 days. Many initial OROV infections can present similarly to chikungunya, dengue, and Zika virus infections. Interestingly, OROV infections can follow a biphasic course with recurrence of symptoms approximately 1 week after initial symptom onset. Concerningly, similar to Zika virus, it appears that vertical transmission of OROV may occur with potentially adverse effects on fetal development including miscarriages. Neuroinvasion of OROV occurs in animal models, and human cases of meningitis, encephalitis, and peri-infectious Guillain-Barré syndrome have all been reported. Diagnosis is either through detection of OROV nucleic acid, OROV immunoglobulin M, or OROV neutralizing antibodies in the serum and/or cerebrospinal fluid. No antiviral treatments are available, and there are no current vaccines. Preventing mosquito and biting midge bites is key. Neurologists should be aware of and report any potential neuroinvasive OROV disease cases to local/state/territorial health departments. ANN NEUROL 2024.

[Key clinical manifestations to differentiate Oropouche fever from dengue and other arboviral diseases: a living systematic reviewRevisão sistemática viva das manifestações clínicas da febre do Oropouche: características-chave para diferenciá-la da dengue e de outras arboviroses]

Objectives

To assess the frequency of symptoms in patients with Oropouche fever and compare them with those observed in patients with dengue and other arboviral diseases.

Methods

A systematic review was conducted following the MOOSE and PRISMA reporting guidelines. The review included studies on acute clinical manifestations in patients with Oropouche fever. Searches were conducted in PubMed, Virtual Health Library, Cochrane Library, and Google Scholar up to September 2024. The symptoms of Oropouche fever were compared to those of dengue and other arboviral diseases. Certainty of evidence was assessed using the GRADE approach.

Results

A total of 23 studies covering 3648 patients with Oropouche fever were included. The most frequent symptoms in patients with Oropouche virus infection were fever (97%) and headache (86%). There was no difference in frequency of fever or headache between patients with Oropouche and dengue. However, odynophagia (28%) and abdominal pain (15%) were more frequent in Oropouche than in dengue, with odds ratios (ORs) of 3.20 and 2.50, respectively. Myalgia (69%) and arthralgia (57%) were less frequent in Oropouche fever than in dengue.

Conclusions

Fever and headache are common in Oropouche virus infection, but do not help discriminate it from dengue. However, odynophagia and abdominal pain are more frequent in patients with Oropouche fever, while myalgia, arthralgia, and rash are more prevalent in dengue. These findings may aid in differential diagnosis in areas of arboviral co-circulation. Further studies on the recurrence and duration of symptoms are needed to improve diagnostic strategies.

The silent invaders: Oropouche and Melao viruses, causes of increased public health risks for the Americas

The Oropouche virus (OROV) is emerging as a major public health threat worldwide, yet for the Americas, it raises complex challenges that intersect with other existing arboviral threats such as Zika (ZIKV), dengue (DENV) and Chikungunya (CHIKV) viruses. Originating from Trinidad and Tobago in 1955, it has spread across the Amazonian Basin and more recently into the Caribbean (Cuba and Haiti) and Europe, highlighting the importance of air travel in its dissemination. OROV and the less studied Melao virus (MELV), pose significant laboratory diagnostic challenges particularly in regions co-endemic with other arboviral diseases, such as dengue and Zika fever. The effects of climate change, particularly in the Caribbean, may exacerbate the transmission of these viruses by exposing human exposure risk to vectors. Public health systems in the Americas are under strain due to complex clinical management of these infections necessitating enhanced surveillance, clinical vigilance, diagnostics and vector control. Vulnerable populations, including pregnant women, elderly, and young children, are at a heightened risk, which raises concerns about the impact on medical tourism in the region. To mitigate the spread and impact of OROV and MELV, recommendations include increased clinical surveillance, improved laboratory diagnostics, public health communication, and strengthened vector controls. Robust research and capacity building (including training and education) efforts are essential to address knowledge gaps and effectively manage future OROV and MELV outbreaks in the Americas.

Oropouche Virus: An Emerging Orthobunyavirus

On 2 February 2024, the Pan American Health Organization/World Health Organization issued an epidemiological alert on rising Oropouche virus (OROV) infections in South America. By 3 August 2024, this alert level had escalated from medium to high. OROV has been a public health concern in Central and South America since its emergence in Brazil in the 1960s. However, the 2024 outbreak marks a turning point, with the sustained transmission in non-endemic regions of Brazil, local transmission in Cuba, two fatalities and several cases of vertical transmission. As of the end of August 2024, 9852 OROV cases have been confirmed. The 2024 OROV outbreak underscores critical gaps in our understanding of OROV pathogenesis and highlights the urgent need for antivirals and vaccines. This review aims to provide a concise overview of OROV, a neglected orthobunyavirus.

Oropouche virus infection: What internal medicine physicians should know

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Oropouche Virus Disease Among U.S. Travelers - United States, 2024

Beginning in late 2023, Oropouche virus was identified as the cause of large outbreaks in Amazon regions with known endemic transmission and in new areas in South America and the Caribbean. The virus is spread to humans by infected biting midges and some mosquito species. Although infection typically causes a self-limited febrile illness, reports of two deaths in patients with Oropouche virus infection and vertical transmission associated with adverse pregnancy outcomes have raised concerns about the threat of this virus to human health. In addition to approximately 8,000 locally acquired cases in the Americas, travel-associated Oropouche virus disease cases have recently been identified in European travelers returning from Cuba and Brazil. As of August 16, 2024, a total of 21 Oropouche virus disease cases were identified among U.S. travelers returning from Cuba. Most patients initially experienced fever, myalgia, and headache, often with other symptoms including arthralgia, diarrhea, nausea or vomiting, and rash. At least three patients had recurrent symptoms after the initial illness, a common characteristic of Oropouche virus disease. Clinicians and public health jurisdictions should be aware of the occurrence of Oropouche virus disease in U.S. travelers and request testing for suspected cases. Travelers should prevent insect bites when traveling, and pregnant persons should consider deferring travel to areas experiencing outbreaks of Oropouche virus disease.

Emergence of Oropouche fever in Latin America: a narrative review

Since its discovery in 1955, the incidence and geographical spread of reported Oropouche virus (OROV) infections have increased. Oropouche fever has been suggested to be one of the most important vector-borne diseases in Latin America. However, both literature on OROV and genomic sequence availability are scarce, with few contributing laboratories worldwide. Three reassortant OROV glycoprotein gene variants termed Iquitos, Madre de Dios, and Perdões virus have been described from humans and non-human primates. OROV predominantly causes acute febrile illness, but severe neurological disease such as meningoencephalitis can occur. Due to unspecific symptoms, laboratory diagnostics are crucial. Several laboratory tests have been developed but robust commercial tests are hardly available. Although OROV is mainly transmitted by biting midges, it has also been detected in several mosquito species and a wide range of vertebrate hosts, which likely facilitates its widespread emergence. However, potential non-human vertebrate reservoirs have not been systematically studied. Robust animal models to investigate pathogenesis and immune responses are not available. Epidemiology, pathogenesis, transmission cycle, cross-protection from infections with OROV reassortants, and the natural history of infection remain unclear. This Review identifies Oropouche fever as a neglected disease and offers recommendations to address existing knowledge gaps, enable risk assessments, and ensure effective public health responses.

Oropouche Virus Exposure in Febrile Patients during Chikungunya Virus Introduction in the State of Amapá, Amazon Region, Brazil

Oropouche orthobunyavirus (OROV) is an arbovirus transmitted by midges that has been involved in outbreaks throughout Central and South America. In Brazil, human cases have been historically concentrated in the northern region of the country. Oropouche fever in humans range from mild clinical signs to rare neurological events, and is considered a neglected tropical disease in Brazil. Due to the clinical similarities to other arboviruses, such as chikungunya and dengue viruses, OROV infections are likely to be underreported. Chikungunya virus (CHIKV) cases in Brazil were first recognized in 2014 in the states of Amapá and Bahia in the north and northeast regions, respectively. Both OROV and CHIKV cause nonspecific symptoms, making clinical diagnosis difficult in a scenario of arbovirus cocirculation. Aiming to investigate OROV transmission during the CHIKV introduction in the state of Amapá located in the Brazilian Amazon, we conducted a retrospective molecular (RT-qPCR) and serological investigation in febrile cases (N = 166) collected between August 2014 and May 2015. All acute serum samples were negative for OROV RNA using RT-qPCR. However, neutralizing antibodies for OROV were detected using a plaque reduction neutralization test (PRNT90) in 10.24% (17/166) of the patients, with neutralizing antibody titers ranging from 20 to ≥640, suggesting the previous exposure of patients to OROV. Regarding CHIKV, recent exposure was confirmed by the detection of CHIKV RNA in 20.25% (33/163) of the patients and by the detection of anti-CHIKV IgM in 28.57% (44/154) of the patients. The additional detection of anti-CHIKV IgG in 12.58% (19/151) of the febrile patients suggests that some individuals had been previously exposed to CHIKV. Whether the OROV exposure reported here occurred prior or during the CHIKV circulation in Amapá, is unknown, but because those arboviral infections share similar clinical signs and symptoms, a silent circulation of enzootic arboviruses during the introduction of exotic arboviruses may occur, and highlights the importance of syndromic cases' surveillance to arboviruses in Brazil.

Outbreak of Oropouche virus in frontier regions in western Amazon

Oropouche virus (OROV) is characterized as a re-emerging arbovirus of great concern for public health, being responsible for several outbreaks of acute fever identified in Latin American countries, registering more than half a million reported cases. The incidence of reports of this virus is intrinsically favored by environmental conditions, in which such characteristics are related to the increase and distribution of the vector population to areas of human traffic. Moreover, there is a problem regarding the lack of diagnosis in Brazil that aggregates the success of the etiologic agent. Thus, by means of molecular techniques, we identified 27 positive cases of the OROV circulating in border locations in western Amazon, with 44.44% (12/27) of the cohort characterized as infected individuals with reported symptoms, mainly ranging from fever, myalgia, and back pain. Among the positive samples, it was possible to obtain a total of 48.14% (13/27) samples to analyze the S and M segments of Oropouche, which showed similarities among the Brazilian sequences. Thus, it was possible to verify the circulation of the OROV in Rondonia and border areas, in which the tracking of neglected arboviruses is necessary for the genomic surveillance of emerging and re-emerging viruses.IMPORTANCEThe western Amazon region is known for outbreaks of acute febrile illnesses, to which the lack of specific diagnostics for different pathogens hinders the management of patients in healthcare units. The Oropouche virus has already been recorded in the region in the 1990s. However, this is the first study, after this record, to perform the detection of individuals with acute febrile illness using a screening test to exclude Zika, dengue, and chikungunya, confirmed by sequencing the circulation of the virus in the state of Rondonia and border areas. We emphasize the importance of including diagnostics for viruses such as Oropouche, which suffers underreporting for years and is related to seasonal periods in Western Amazon locations, a factor that has a direct influence on public health in the region. In addition, we emphasize the importance of genomic surveillance in the elucidation of outbreaks that affect the resident population of these locations.

Transmission risk of Oropouche fever across the Americas

BACKGROUND

Vector-borne diseases (VBDs) are important contributors to the global burden of infectious diseases due to their epidemic potential, which can result in significant population and economic impacts. Oropouche fever, caused by Oropouche virus (OROV), is an understudied zoonotic VBD febrile illness reported in Central and South America. The epidemic potential and areas of likely OROV spread remain unexplored, limiting capacities to improve epidemiological surveillance.

METHODS

To better understand the capacity for spread of OROV, we developed spatial epidemiology models using human outbreaks as OROV transmission-locality data, coupled with high-resolution satellite-derived vegetation phenology. Data were integrated using hypervolume modeling to infer likely areas of OROV transmission and emergence across the Americas.

RESULTS

Models based on one-support vector machine hypervolumes consistently predicted risk areas for OROV transmission across the tropics of Latin America despite the inclusion of different parameters such as different study areas and environmental predictors. Models estimate that up to 5 million people are at risk of exposure to OROV. Nevertheless, the limited epidemiological data available generates uncertainty in projections. For example, some outbreaks have occurred under climatic conditions outside those where most transmission events occur. The distribution models also revealed that landscape variation, expressed as vegetation loss, is linked to OROV outbreaks.

CONCLUSIONS

Hotspots of OROV transmission risk were detected along the tropics of South America. Vegetation loss might be a driver of Oropouche fever emergence. Modeling based on hypervolumes in spatial epidemiology might be considered an exploratory tool for analyzing data-limited emerging infectious diseases for which little understanding exists on their sylvatic cycles. OROV transmission risk maps can be used to improve surveillance, investigate OROV ecology and epidemiology, and inform early detection.