Molecular #Surveillance for #Oropouche, #Mayaro, West Nile, and Saint Louis #Encephalitis Viruses, #Brazil, 2019–2025

 

Abstract

To assess the circulation of Oropouche, Mayaro, West Nile, and St. Louis encephalitis viruses, we tested samples from 824 patients with acute febrile illness, 3,484 mosquitoes, and 113 nonhuman primates from northern Minas Gerais, Brazil. All samples were negative for dengue, Chikungunya, and Zika virus. One imported Oropouche virus infection was detected.

Source: Emerging Infectious Diseases Journal, https://doi.org/10.3201/eid3212.260870

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#Oropouche Fever #Outbreak, #Havana, #Cuba, June–September 2024

 

Abstract

Oropouche fever emerged nationwide in Cuba in 2024. We investigated the outbreak in Havana; of 549 suspected cases, 189 (34.4%) were confirmed. No cases were severe. Incidence was 8.9/100,000 population and was highest in adults 27–59 years of age (10.2/100,000 population). Three infants tested positive. Dengue cocirculation challenged surveillance.

Source: 

Link: https://wwwnc.cdc.gov/eid/article/32/12/25-1334_article

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#Vector competence of #Aedes albopictus and #Culex quinquefasciatus for #Oropouche virus

 

Abstract

Oropouche virus (OROV) is an arthropod-borne virus transmitted mainly by Culicoides paraensis midges in Latin America and the Caribbean, though evidence suggests occasional transmission by mosquitoes. Oropouche fever has been reported primarily in the Amazon Basin since the 1950s. In 2024, the number of Oropouche fever cases rose sharply and spread beyond the Amazon region, which has been associated with the emergence of a new reassortant OROV strain. We assessed whether increased case numbers could be explained by enhanced replication or transmission of the reassortant strain in peri-urban Culex quinquefasciatus and Aedes albopictus. Laboratory colonies established from Salvador, Brazil were orally exposed to the ancestral OROV strain BeAn 19991 or the contemporary strain 240023 (10⁴–10⁶ PFU/mL), and viral replication was quantified in bodies, legs, and saliva. To evaluate the influence of mosquito genotype on infection outcomes, infection rates were compared between Ae. albopictus from Salvador City (Brazil) and Houston (USA). In Cx. quinquefasciatus, the outbreak strain replicated less efficiently than the historical strain at low viral doses but not at high infection doses. Regardless of strain or dose, vector competence was extremely low, with only 0–1% of mosquitoes exhibiting infectious OROV particles in their saliva after extrinsic incubation. Conversely, Ae. albopictus showed consistently higher body infection rates for the 240023 strain than for BeAn 19991 at both low and high doses. However, overall transmission potential remained limited: only 0–6.4% of leg or saliva samples were positive across OROV strains and doses. The higher infection rates of the 240023 strain was consistent across both Ae. albopictus genotypes, but infectious saliva was detected only in mosquitoes from the Salvador line (up to 20%) and not in the Houston line (0%). Taken together, this suggests that the recent geographic expansion of OROV is unlikely to be driven by a vector shift from midges to these mosquitoes. Importantly, our findings do indicate higher infectivity of the 240023 strain in Ae. albopictus across different mosquito lines which may have future implications for further adaptation to OROV.

Source: 

Link: https://doi.org/10.1371/journal.pntd.0014656

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#Oropouche virus #infection in #pregnant women in #Rio de Janeiro, #Brazil: a prospective cohort study

 

Summary

Background

Although adverse maternal and infant outcomes have been reported following Oropouche virus infection, the frequencies of these outcomes have not been compared with those in uninfected pregnancies. We followed up pregnant women from areas with Oropouche virus transmission in Rio de Janeiro state, Brazil, to evaluate potential adverse maternal and infant outcomes following Oropouche virus exposure.

Methods

In this prospective cohort study across the state of Rio de Janeiro, Brazil, we included pregnant women receiving prenatal care in municipalities with or at high risk of Oropouche virus outbreaks. Inclusion criteria were: ongoing risk of Oropouche virus infection at the time of prenatal visit; prenatal care at one of the participating sites; and willingness and ability to consent to and participate in the study. Exclusion criteria included infection with other arboviruses and fetal chromosomal abnormalities. Maternal blood, urine, and saliva were collected and tested for Oropouche virus by RT-PCR at enrolment and pregnancy endpoints. IgG and IgM serologies from maternal blood, placental tissue PCR, and immunohistochemistry were done. Confirmed infections were defined by: positive Oropouche virus PCR in blood, urine, saliva, or placenta; positive Oropouche virus placental immunohistochemistry; or Oropouche virus-specific IgM or IgG seroconversion. Possible infection was defined as one positive IgM result without a positive PCR. Negative results ruled out infection. Adverse maternal outcomes (reported by study investigators following up participants at study sites) were maternal death or disability, fetal loss, or haemorrhage; adverse infant outcomes were neonatal death or malformations. Relative risks adjusted for maternal age, other congenital infections, and use of tobacco, alcohol, and drugs during pregnancy for adverse maternal and infant outcomes were calculated.

Findings

Between Nov 29, 2024, and Oct 8, 2025, 544 participants were enrolled: 130 (24%) with confirmed, 143 (26%) with possible, and 271 (50%) with no Oropouche virus infection. The median cycle threshold value of RT-PCR was 29·7 (IQR 25·8–34·9). Among the 130 women with confirmed infection, 104 (80%) developed detectable IgG antibodies. Symptoms were present in 80 (62%) women with confirmed infection, not necessarily associated with adverse outcomes (adjusted relative risk [aRR] 0∙84 [95% credible interval 0∙51–1∙21]). By the end of follow-up, the pregnancies of 119 women with confirmed infection and 193 with no infection had resulted in livebirth, stillbirth, or miscarriage; 105 (88%) women with confirmed infection had livebirths and 187 (97%) women without infection had livebirths. Adverse maternal outcomes occurred in 21 (18%) women with confirmed infection and 14 (7%) women with no infection (aRR 2∙90 [1∙52–5∙35]). Fetal loss and haemorrhage risk were three times higher in women with confirmed infection than in those with no infection (aRR 3∙08 [1∙28–7∙29] for fetal loss and 2∙79 [1∙22–6∙21] for haemorrhage). The aRR for adverse infant outcomes was 9∙18 (1∙89–47∙88). CNS abnormalities occurred in eight (8%) infants of mothers with confirmed infection and in no infants of mothers with no infection.

Interpretation

Oropouche virus infection during pregnancy is associated with severe maternal and infant outcomes, including maternal haemorrhage, fetal loss, and infant CNS abnormalities.

Funding

The Carlos Chagas Filho Foundation for Research Support of the State of Rio de Janeiro (FAPERJ), the National Council for Scientific and Technological Development (CNPq), the Brazilian Ministry of Health, the Oswaldo Cruz Foundation (Fiocruz), and the European Health and Digital Executive Agency.

Translation

For the Portuguese translation of the abstract see Supplementary Materials section.

Source: 

Link: https://doi.org/10.1016/S1473-3099(26)00493-7

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Integrated in vivo and transcriptomic analyses of lethal #Oropouche virus #infection reveal suppression of pathogenic host responses by #antiviral therapy

 

Abstract

Oropouche virus (OROV) is an emerging arbovirus responsible for large outbreaks of febrile illness in Central and South America, with increasing reports of severe neurological disease and fatal outcomes. Despite its growing public health impact, no approved antiviral therapies or vaccines are currently available. Here, we show that favipiravir, a broad-spectrum nucleoside analogue, robustly suppresses OROV replication and disease in vivo. In a lethal Syrian hamster model, favipiravir treatment provided complete protection against OROV infection, preventing viral dissemination to peripheral organs and the central nervous system, and remained highly effective when administration was initiated after infection. In contrast, insufficient antiviral control resulted in viral neuroinvasion and fatality. To define host responses associated with OROV pathogenesis and their modulation by antiviral therapy, we performed transcriptomic profiling of liver and brain tissues. OROV infection induced interferon-driven inflammatory programs accompanied by marked disruption of metabolic and tissue homeostatic pathways, whereas these transcriptional signatures were largely abrogated by favipiravir treatment. Together, our findings identify favipiravir as a potent antiviral candidate against OROV and provide the first in vivo, tissue-resolved transcriptomic framework of OROV infection, linking effective viral suppression with the prevention of neuroinvasion and pathogenic host responses. These results highlight antiviral intervention as a viable strategy to mitigate OROV-associated disease and mortality.

Source: 

Link: https://doi.org/10.1371/journal.ppat.1014647

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#Teratogenic Effects and Outcomes of #Congenital #Oropouche Virus Infection: Current Evidence, Pathophysiological Mechanisms, and Research Priorities

 

Abstract

Background: 

Oropouche virus (OROV), an Orthobunyavirus endemic to Latin America, has recently emerged as a pathogen of concern in pregnancy following reports of vertical transmission, fetal demise, congenital anomalies, and neonatal disease. The unprecedented 2023–2025 outbreaks in Latin America have expanded the geographic distribution of OROV and renewed concerns regarding its potential as an emerging human teratogen. 

Methods: 

We conducted a narrative comprehensive review of the literature focusing on epidemiology, maternal–fetal transmission, placental infection, experimental models, fetal and neonatal outcomes, and comparisons with other congenital arboviral infections. 

Results: 

Increasing evidence supports the ability of OROV to infect the placenta, cross the maternal–fetal interface, and invade fetal tissues. Human cases have documented miscarriage, stillbirth, fetal demise, microcephaly, ventriculomegaly, cerebral atrophy, corpus callosum abnormalities, posterior fossa defects, arthrogryposis, and neonatal death following maternal infection. Viral RNA and OROV-specific antibodies have been detected in placental, fetal, and neonatal samples, providing direct evidence of congenital infection. Experimental studies using trophoblast cultures, placental organoids, neural progenitor cells, brain organoids, and animal models have confirmed placental susceptibility, vertical transmission, fetal neurotropism, and disruption of neurodevelopment. The congenital phenotype shares important similarities with congenital Zika syndrome and other neurotropic arboviral infections. 

Conclusions: 

OROV is newly and increasingly recognized as a vertically transmissible neurotropic arbovirus with potential teratogenic effects. Although biological plausibility is supported by converging clinical and experimental findings, prospective epidemiological studies are urgently needed to quantify risks, identify determinants of fetal injury, and define long-term outcomes among affected children.

Source: 

Link: https://doi.org/10.3390/v18101101

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#Oropouche virus disrupts #neurodevelopment and exhibits #congenital infection potential

 

Abstract

Oropouche virus (OROV) historically caused a self-limiting disease, yet recent strains have been clinically linked to congenital infection and neurodevelopmental disease. These observations highlight the need to study OROV as a congenital pathogen. Here, using both a historical and currently circulating strain, we show OROV infects neurons across differentiation states in human forebrain organoids. Compared with the neurotropic congenital pathogen Zika virus (ZIKV), OROV exhibits a heightened capacity for neuroinfection and pathology in both forebrain organoids and neonatal mice. The increased permissiveness of OROV is driven, in part, by a broader neuronal tropism and a relative insensitivity to neuronal type I interferon-mediated antiviral responses. Consistent with clinical observations, neonatal neuroinfection results in rapid and severe neuropathology marked by cerebral hemorrhage. Finally, using a transient type I interferon-blockade model, we demonstrate that OROV can productively infect the murine placenta and cause fetal growth restriction. Together, our complementary models support a unified framework in which placental and fetal barriers limit productive fetal brain infection, yet OROV exhibits marked neurotropism and neuropathogenic potential upon gaining access to developing neural tissues. These findings reinforce the need for vigilant monitoring of OROV as an emerging pathogen associated with adverse pregnancy outcomes and congenital disease.

Source: 

Link: https://doi.org/10.1038/s41467-026-77859-5

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#Oropouche virus #outbreaks in northeast #Brazil between 2024–25 are characterized by sustained #transmission and spread to newly affected areas

 

Abstract

Oropouche virus (OROV) has recently expanded in Brazil, establishing transmission in non-endemic regions. This study aims to integrate epidemiological and molecular data to investigate OROV spread in Northeast (NE) Brazil between 2024 and 2025. OROV cases were analyzed regarding ecological risk factors and geographical clustering. Additionally, we sequenced 65 new OROV genomes from the Northeast states of Pernambuco, Paraíba, and Sergipe to infer the virus’s spatiotemporal dynamics in NE Brazil. A total of 2,806 confirmed cases were reported between March 2024 and April 2025, affecting 170 municipalities across eight out of nine NE states, with highly heterogeneous incidence. An ecological shift was observed, with OROV transmission moving from Atlantic Forest areas in 2024 to humid Caatinga zones in 2025. Phylogenetic reconstruction revealed multiple independent viral introductions in Northeast in 2024, including two in Pernambuco. The first, originating from the central Amazonas, became the main driver of local transmission and subsequently spread to Sergipe and Paraíba, causing outbreaks in 2024 and 2025, respectively. The second introduction remained restricted within Pernambuco. While several Northeast municipalities reported high OROV incidence, Jaqueira (Pernambuco) emerged as a key hub for regional viral spread. OROV showed sustained transmission in the region over a two-year period, characterized by marked spatiotemporal displacement consistent with short-lived, rapidly spreading outbreaks, followed by cryptic transmission and subsequent dissemination to new areas, ultimately driving renewed intense outbreaks.

Source: 

Link: https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0014171

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#Culicoides (Diptera: Ceratopogonidae) in Extra-Amazonian #Oropouche #Outbreak Areas of Minas Gerais, #Brazil: #Ecological Insights into Virus Transmission

 

Abstract

Oropouche fever (OF), caused by Oropouche virus (OROV), has expanded beyond its Amazonian range into Minas Gerais (MG), Brazil, raising concern about transmission in extra-Amazonian Atlantic Forest landscapes. Critical gaps persist regarding Culicoides vector communities, anthropophily, and climate-sensitive transmission risk in these newly affected regions. We conducted targeted entomological surveys outbreak-driven by human OF cases, standardized across five MG communities using CDC light traps and Protected Human Attraction (PHA) to characterize Culicoides composition. Females of Culicoides underwent RT-qPCR for OROV (n = 819) and physiological assessment (n = 312). We developed an entomological alert framework that integrates blood-fed abundance, minimum infection rate (MIR) upper confidence bounds, and environmental drivers (i.e., mean temperature, relative humidity and precipitation) via generalized additive mixed models, which explained 68% of the variability in Culicoides abundance and the alert index across communities. We collected 1171 Culicoides individuals representing five species (C. leopoldoi, C. paraensis, C. pusillus, C. foxi, and C. limai). C. leopoldoi (79.1%) and C. paraensis (20.3%) were the predominant species; notably, C. paraensis is recognized as the primary vector of OROV in the Americas. C. paraensis was documented for the first time in all five outbreak areas and dominated PHA captures (90%), suggesting anthropophily. Although no specimens tested OROV-positive (consistent with expected field infection rates of 0.01–1%), MIR upper bounds reached 132/1000 in low-sample settings and humidity and temperature strongly modulated abundance. This operational baseline and alert index transform virologically negative, sparse surveillance data into prioritized targets for intensified sampling and vector control during early, low-prevalence phases, when containment of OROV’s extra-Amazonian spread is still achievable.

Source: 

Link: https://www.mdpi.com/1999-4915/18/3/361

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#Oropouche virus infects primary #human #intestinal #organoids and is inhibited by type I and III interferon treatment

 

ABSTRACT

Oropouche virus (OROV), a neglected arbovirus, has historically been considered a self-limiting infection associated with febrile illness. However, the recent surge in cases since late 2023 has been marked by atypical outcomes, highlighting its underestimated clinical impact. Gastrointestinal symptoms such as diarrhea have also been reported, but the prevalence and mechanistic insight remain largely elusive. Here, through a meta-analysis of 12 identified clinical studies, we revealed a pooled prevalence of diarrhea as 15% (95% CI, 10%–20%) among the Oropouche patient population. In primary human intestinal organoid-based experimental models, we demonstrated productive infection by both a recent patient isolate (OROV-2024) and a historical strain (Be An19991). This is shown by the accumulation of intracellular OROV RNA, release of infectious particles, and immunostaining of OROV glycoprotein Gc. Interestingly, OROV infection mildly triggered the expression of type III interferons, but this endogenous response was insufficient to limit viral replication. In contrast, exogenous treatment with type I and III interferons strongly inhibited OROV replication, with interferon-alpha completely abolishing infectious virus production. Together, these results suggest the human intestine as a potential target organ for OROV infection and highlight interferons as potential therapeutic candidates.

Source: 

Link: https://journals.asm.org/doi/full/10.1128/mbio.03003-25?af=R

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A VLP-based #mRNA #vaccine elicits potent humoral and cellular #immunity against #Oropouche virus

 

ABSTRACT

Oropouche virus (OROV) is reemerging in the Americas, along with a growing threat to global public health. Recent outbreaks have witnessed the first reported fatalities, vertical transmissions, and intercontinental importations of OROV, underscoring its expanding risk. Despite this, no vaccines or specific therapeutics are available, and fundamental research on OROV vaccinology and antigenicity remains limited. Here, we show that co-expression of the M polyprotein and nucleocapsid protein (NP) drives the assembly of OROV virus-like particles (VLPs) with high immunogenicity. Using the prototype strain OROV/sloth/Brazil/PA-UG-BeAn19991/1960, we developed an mRNA vaccine, M/N-vac, encoding these VLPs. Immunization with M/N-vac in mice elicited robust OROV-specific IgG and pseudovirus-neutralizing antibodies that cross-reacted with a contemporary circulating strain, hOROV/Brazil/AM-UKY-AM0088/2024. The vaccine also induced a durable, antigen-specific Th1-biased cellular immune response characterized by high-level interferon-gamma secretion. Additionally, we identified a highly conserved potential immunodominant epitope in BALB/c, N2-3, within the nucleocapsid protein. Furthermore, the VLP-encoding mRNA vaccine induced stronger OROV-specific humoral and cellular immune responses than the VLP protein vaccine. In vivo results based on immunization with M/N-vac demonstrate VLP-based vaccines to be a promising broad-spectrum strategy against OROV while providing novel insights into their antigenicity and design.

Source: 

Link: https://journals.asm.org/doi/full/10.1128/mbio.03653-25?af=R

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Serological and viral #prevalence of #Oropouche virus (OROV): A systematic review and meta-analysis from 2000–24 including #human, #animal, and #vector #surveillance studies

 

Abstract

Background

Oropouche virus (OROV) is an emerging arbovirus primarily transmitted by biting midges and is increasingly recognized as a public health threat in Central and South America. With over 11,000 confirmed cases reported in 2024, a ten-fold increase from the previous year, its transmission dynamics and true burden remain poorly understood due to diagnostic challenges and fragmented surveillance systems.

Objective

This systematic review and meta-analysis (SRMA) synthesizes OROV prevalence data in humans and summarizes the available data for vectors and animal hosts sampled between 2000 and 2024 to provide updated estimates and identify key surveillance gaps.

Methods

We systematically searched Web of Science, PubMed, Embase, Medline, and LILACS for OROV seroprevalence and viral prevalence studies in human, insect, and animal populations, published up to September 12, 2024. The review protocol was registered with PROSPERO (CRD42024551000). Studies were extracted in duplicate, and data were meta-analyzed using generalized linear mixed-effects models. Risk of bias was appraised using a modified Joanna Briggs Institute checklist.

Results

We included 71 articles reporting serological or viral prevalence of OROV across nine countries. Between 2000–2024, pooled human seroprevalence among individuals with febrile illness or suspected of Oropouche infection was 12.6% [95% CI 5.3-26.9%] across four South American countries and seroprevalence of 1.1% [95% CI 0.5-2.3%] was observed in asymptomatic groups. Viral prevalence among individuals with febrile illness or suspected of Oropouche infection was 1.5% [0.8-3.0%] across seven South American countries and Haiti. Most studies used convenience sampling and RT-PCR or hemagglutination assays. In vector populations, positive OROV prevalence in Aedes aegypti and Culex quinquefasciatus was reported in two of 18 sources, while 10.0% and 7.5% animal host prevalence was reported in dogs and cattle, respectively. We found high risk of bias in 11.3% of studies in our critical appraisal, with most animal, human, and vector studies falling in the moderate risk of bias range.

Conclusions

Despite rising numbers of OROV reported cases, prevalence estimates remain limited by sparse surveillance and variable methodology. This review highlights the urgent need for standardized serological assays, community-based studies, and expanded surveillance in animal and vector reservoirs. A One Health approach is essential to monitor OROV transmission and inform regional preparedness efforts.

Source: 

Link: https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0013340

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#Remdesivir as a potent #antiviral against prototype and current #epidemic #Oropouche virus #strains (BeAn19991 and PE-IAM4637)

 

Highlights

• We generated a recombinant reporter OROV that expresses the eGFP fluorescent protein in infected cells.

• We found that remdesivir efficiently inhibited the replication of Oropouche virus (OROV) using this reporter OROV.

• We demonstrated strain-dependent differences in the replication efficiency of OROV.

Abstract

The Oropouche virus (OROV), an orthobunyavirus transmitted by biting midges, is the causative agent of Oropouche fever, which has caused multiple outbreaks in South and Central America. During the most recent epidemic in 2023–2025, more than 25,000 laboratory-confirmed cases were reported in Brazil, and no licensed antivirals have been reported to be effective date. In this study, we generated a recombinant OROV-expressing enhanced green fluorescent protein (rOROV/GFP) to facilitate rapid and sensitive antiviral evaluation. Growth kinetics demonstrated that rOROV/GFP replicated less efficiently than wild-type rOROV and that the historical prototype strain (BeAn19991) exhibited higher replication efficiency than the recent epidemic isolate (PE-IAM4637) in both Vero E6 and Huh7 cells. Using this system, we evaluated the antiviral activity of ribavirin, favipiravir (T-705), and remdesivir against OROV. All three compounds inhibited OROV replication in a dose-dependent manner, with remdesivir showing the greatest potency (IC₅₀ values of 0.31 µM). Taken together, our findings highlight remdesivir as a promising candidate for the treatment of Oropouche fever caused by OROV. Furthermore, we established rOROV/GFP as a powerful tool for antiviral drug screening.

Source: 

Link: https://www.sciencedirect.com/science/article/pii/S0168170225001583?via%3Dihub

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Effective #treatment of advanced #Oropouche virus, Rift Valley fever virus, and Dabie #bandavirus #infections with 4'-fluorouridine

 

ABSTRACT

Oropouche virus (OROV), Rift Valley fever virus (RVFV), and Dabie bandavirus (DBV) are significant re-emerging and emerging human pathogens with major public health implications. Notably, the ongoing OROV disease epidemic spanning South America, Central America, and the Caribbean now exceeds 11,000 cases, including several fatalities and reports of neurological disease and congenital abnormalities associated with infection. Rift Valley fever outbreaks continue to plague sub-Saharan Africa, and DBV, the etiologic agent of severe fever with thrombocytopenia syndrome (SFTS), is expanding its reach throughout several Asian countries. No vaccines or approved therapies are available to prevent or treat these viral infections. Here, we report on the antiviral activity and protective efficacy of the ribonucleoside analog, 4′-fluorouridine (4′-FlU), against OROV, RVFV, and DBV in cell culture and murine models of infection and disease. In cell culture, the potency of 4′-FlU was in the low nanomolar (OROV) to low micromolar (RVFV and DBV) range. In vivo, prophylactic oral dosing of the compound was fully protective against all three viruses in their respective mouse infection models. Importantly, post-exposure and therapeutic interventions of advanced infections in mice also responded remarkably well to treatments. Our findings extend the broad-spectrum antiviral capacity of 4′-FlU and support the compound’s further development for treating severe bunyaviral infections.

IMPORTANCE

Re-emerging and emerging viral diseases, for which no approved vaccines or therapeutics exist, pose a significant public health threat in affected areas of the world. Antiviral drugs that are broadly active against multiple pathogenic viruses are much needed. Our findings demonstrating robust protection conferred by treatment with 4′-fluorouridine (4′-FlU) in viral infection models for Oropouche fever, Rift Valley fever, and severe fever with thrombocytopenia syndrome support the continuing development of this promising broad-spectrum antiviral drug candidate for the treatment of these notable viral diseases.

Source: mBio, https://journals.asm.org/doi/full/10.1128/mbio.01467-25?af=R

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#Persistence and Active #Replication Status of #Oropouche Virus in Different Body Sites: Longitudinal Analysis of a #Traveler Infected with a Strain Spreading in Latin America

Abstract

An unprecedented outbreak of Oropouche virus (OROV) is occurring in the Americas, characterized by thousands of confirmed cases and a wide geographical spread, including areas outside the Amazon Basin. Little is known about this neglected arbovirus regarding its pathophysiological aspects and potentially different transmission modes. This study describes the clinical course of a man who returned from a trip to Cuba and presented to our hospital 4 days after the onset of febrile symptoms. The patient was diagnosed with Oropouche fever and was followed for 177 days after the onset of symptoms. We performed a longitudinal investigation of the samples collected from several body sites (whole blood, serum, urine, and semen) with the aim of providing further insights into OROV infection dynamics, using the detection of antigenomic RNA as a marker of active viral replication. Clinical samples that were longitudinally collected over the course of OROV infection showed consistently higher amounts of antigenomic RNA compared to genomic RNA, even after viral clearance from serum. Moreover, our case study showed the persistence of OROV RNA in serum of less than 15 days from the onset of symptoms, as compared to up to one month in urine, three months in semen, and four months in whole blood. Our study suggests that Oropouche virus may persist in an actively replicating state in different body sites for long periods of time, with important implications for transmission dynamics. Furthermore, our results provide a diagnostic indication, suggesting that serum is inferior to both urine and whole blood as preferred diagnostic samples. Further studies are needed to determine the pathogenetic implications of these findings, as they have been derived from a single case and must be confirmed using a larger number of cases.

Source: Viruses, https://www.mdpi.com/1999-4915/17/6/852

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#Neuroinvasive #Oropouche virus in a patient with #HIV from extra-Amazonian #Brazil

{Excerpt}

A novel reassortant Oropouche virus (OROV) lineage (with medium [M], large [L], and small [S] RNA segments: M1L2S2) has driven Brazil's largest and most geographically widespread OROV epidemic, expanding beyond the endemic Amazon basin to establish local transmission across multiple Brazilian states and other previously unaffected Latin American countries. The rapid spread of this lineage underscores its evolutionary potential and reinforces its significance as a public health threat.1 Similar to chikungunya and Zika viruses, expanding arboviruses can exhibit unexpected clinical and epidemiological shifts, including vertical transmissions, neuroinvasive effects, and potentially fatal outcomes.2–4 Although OROV typically causes self-limited febrile illness, accumulating clinical and experimental evidence suggests neurotropic potential.5 This Correspondence describes the first confirmed case of neuroinvasive OROV infection caused by the emergent M1L2S2 lineage in extra-Amazonian Brazil, highlighting a potential synergistic mechanism of CNS invasion facilitated by HIV-induced immune dysregulation.

(...)

Source: Lancet Infectious Diseases, https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(25)00352-4/fulltext?rss=yes

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Emergence of #Oropouche Virus in Espírito Santo State, #Brazil, 2024

Abstract

Oropouche virus (OROV), historically endemic to the Amazon, had spread to nearly all Brazil states by 2024; Espírito Santo emerged as a transmission hotspot in the Atlantic Forest biome. We characterized the epidemiologic factors driving OROV spread in nonendemic southeast Brazil, analyzing environmental and agricultural conditions contributing to viral transmission. We tested samples from 29,080 suspected arbovirus-infected patients quantitative reverse transcription PCR for OROV and dengue, chikungunya, Zika, and Mayaro viruses. During March‒June 2024, the state had 339 confirmed OROV cases, demonstrating successful local transmission. Spatial analysis revealed that most cases clustered in municipalities with tropical climates and intensive cacao, robusta coffee, coconut, and pepper cultivation. Phylogenetic analysis identified the Espírito Santo OROV strains as part of the 2022–2024 Amazon lineage. The rapid spread of OROV outside the Amazon highlights its adaptive potential and public health threat, emphasizing the need for enhanced surveillance and targeted control measures.

Source: US Centers for Disease Control and Prevention, https://wwwnc.cdc.gov/eid/article/31/6/24-1946_article

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Estimation of #Incubation Period for #Oropouche Virus Disease among #Travel-Associated Cases, 2024–2025

Abstract

Determining the incubation period of Oropouche virus disease can inform clinical and public health practice. We analyzed data from 97 travel-associated cases identified by the Centers for Disease Control and Prevention (n = 74) or the GeoSentinel Network (n = 13) and 10 cases from published literature. Using log-normal interval-censored survival analysis, we estimated the median incubation period to be 3.2 (95% CI 2.5–3.9) days. Symptoms developed by 1.1 (95% CI 0.6–1.5) days for 5% of patients, 9.7 (95% CI 6.9–12.5) days for 95% of patients, and 15.4 (95% CI 9.6–21.3) days for 99% of patients. The estimated incubation period range of 1–10 days can be used to assess timing and potential source of exposure in patients with Oropouche symptoms. For patients with symptom onset >2 weeks after travel, clinicians and public health responders should consider the possibility of local vectorborne transmission or alternative modes of transmission.

Source: US Centers for Disease Control and Prevention, https://wwwnc.cdc.gov/eid/article/31/7/25-0468_article

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#Vector competence for #Oropouche virus: A systematic #review of pre-2024 experiments

Abstract {1}

The 2023–24 epidemic of Oropouche fever in the Americas and the associated ongoing outbreak in Cuba suggests a potential state shift in the epidemiology of the disease, raising questions about which vectors are driving transmission. In this study, we conduct a systematic review of vector competence experiments with Oropouche virus (OROV, Orthobunyavirus) that were published prior to the 2023–24 epidemic season. Only seven studies were published by September 2024, highlighting the chronic neglect that Oropouche virus (like many other orthobunyaviruses) has been subjected to since its discovery in 1954. Two species of midge (Culicoides paraensis and C. sonorensis) consistently demonstrate a high competence to transmit OROV (~30%), while mosquitoes (including both Aedes and Culex spp.) exhibited an infection rate consistently below ~20%, and showed limited OROV transmission. Further research is needed to establish which vectors are involved in the ongoing outbreak in Cuba, and whether local vectors and wildlife communities create any risk of establishment in non-endemic regions.

Abstract {2}

Oropouche virus has recently become an urgent threat to public health in Central and South America. OROV is mainly transmitted by biting midges; however, some public health agencies and scientific sources note that some mosquito species transmit the virus. We conducted a systematic review of literature prior to the current epidemic, and identified seven studies that experimentally tested the ability of vectors to become infected with, and transmit OROV (i.e., that assessed their vector competence). These studies have consistently found that biting midges become infected at higher rates than mosquitoes, which rarely transmit the virus. It is unclear which vectors are responsible for transmitting OROV in the current outbreak. Existing published data support the observation that biting midges are likely to be significant vectors compared to mosquitoes, which are comparatively incompetent. However, increased vector surveillance and pathogen testing, and additional vector competence experiments using current OROV strains, are urgently needed.

Source: PLoS Neglected Tropical Diseases, https://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0013014

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The spatiotemporal #ecology of #Oropouche virus across Latin #America: a multidisciplinary, laboratory-based, modelling study

Summary

Background

Latin America has been experiencing an Oropouche virus (OROV) outbreak of unprecedented magnitude and spread since 2023–24 for unknown reasons. We aimed to identify risk predictors of and areas at risk for OROV transmission.

Methods

In this multidisciplinary, laboratory-based, modelling study, we retrospectively tested anonymised serum samples collected between 2001 and 2022 for studies on virus epidemiology and medical diagnostics in Bolivia, Brazil, Colombia, Costa Rica, Ecuador, and Peru with nucleoprotein-based commercial ELISAs for OROV-specific IgG and IgM antibodies. Serum samples positive for IgG from different ecological regions and sampling years were tested against Guaroa virus and two OROV glycoprotein reassortants (Iquitos virus and Madre de Dios virus) via plaque reduction neutralisation testing (PRNT) to validate IgG ELISA specificity and support antigenic cartography. Three OROV strains were included in the neutralisation testing, a Cuban OROV isolate from the 2023–24 outbreak, a contemporary Peruvian OROV isolate taken from a patient in 2020, and a historical OROV isolate from Brazil. We analysed the serological data alongside age, sex, cohort, and geographical residence data for the serum samples; reported OROV incidence data; and vector occurrence data to explore OROV transmission in ecologically different regions of Latin America. We used the MaxEnt machine learning methodology to spatially analyse and predict OROV infection risk across Latin America, fitting one model with presence–absence serological data (seropositive results were recorded as presence and seronegative results were recorded as absence) and one model with presence-only, reported incidence data from 2024. We computed marginal dependency plots, variable contribution, and permutation metrics to analyse the impact of socioecological predictors and fitted a generalised linear mixed-effects model with logit link and binary error structure to analyse the potential effects of age, sex, or cohort type bias and interactions between age or sex and cohort type in our serological data. We conducted antigenic cartography and evolutionary characterisations of all available genomic sequences for all three OROV genome segments from the National Center for Biotechnology Information, including branch-specific selection pressure analysis and the construction of OROV phylogenetic trees.

Findings

In total, 9420 serum samples were included in this study, representing 76 provinces in the six Latin American countries previously mentioned. The sex distribution across the combined cohorts was 48% female (4237 of 8910 samples with available data) and 52% male (4673 of 8910 samples) and the mean age was 29·5 years (range 0–95 years). The samples were collected from census-based cohorts, cohorts of healthy individuals, and cohorts of febrile patients receiving routine health care. The average OROV IgG antibody detection rate was 6·3% (95% CI 5·8–6·8), with substantial regional heterogeneity. The presence–absence, serology-based model predicted high-risk areas for OROV transmission in the Amazon River basin, around the coastal and southern areas of Brazil, and in parts of central America and the Caribbean islands, consistent with case data from the 2023–24 outbreak reported by the Pan American Health Organization. Areas with a high predicted risk of OROV transmission with the serology-based model showed a statistically significant positive correlation with state-level incidence rates per 100 000 people in 2024 (generalised linear model, p=0·0003). The area under the curve estimates were 0·79 (95% CI 0·78–0·80) for the serology-based model and 0·66 (95% CI 0·65–0·66) for the presence-only incidence-based model. Longitudinal diagnostic testing of serum samples from cohorts of febrile patients suggested constant circulation of OROV in endemic regions at varying intensity. Climate variables accounted for more than 60% of variable contribution in both the serology-based and incidence-based models. Antigenic cartography, evolutionary analyses, and in-vitro growth comparisons showed clear differentiation between OROV and its glycoprotein reassortants, but not between the three different OROV strains. PRNT titres of OROV-neutralising serum samples were strongly correlated between all three tested OROV isolates (r>0·83; p<0·0001) but were not correlated with the two glycoprotein reassortants.

Interpretation

Our data suggest that climatic factors are major drivers of OROV spread and were potentially exacerbated during 2024 by extreme weather events. OROV glycoprotein reassortants, but not individual OROV strains, probably have distinct antigenicity. Preparedness for OROV outbreaks requires enhanced diagnostics, surveillance, and vector control in current and future endemic areas, which could all be informed by the risk predictions presented in this Article.

Source: Lancet Infectious Diseases, https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(25)00110-0/fulltext?rss=yes

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