Real-time RT-PCR for Venezuelan equine encephalitis complex, Madariaga, and Eastern equine encephalitis viruses: application in human and mosquito public health surveillance in Panama.

Eastern equine encephalitis virus (EEEV), Madariaga virus (MADV), and Venezuelan equine encephalitis virus complex (VEEV) are New World alphaviruses transmitted by mosquitoes. They cause febrile and sometimes severe neurological diseases in human and equine hosts. Detecting them during the acute phase is hindered by non-specific symptoms and limited diagnostic tools. We designed and clinically assessed real-time reverse transcription polymerase chain reaction assays (rRT-PCRs) for VEEV complex, MADV, and EEEV using whole-genome sequences. Validation involved 15 retrospective serum samples from 2015 to 2017 outbreaks, 150 mosquito pools from 2015, and 118 prospective samples from 2021 to 2022 surveillance in Panama. The rRT-PCRs detected VEEV complex RNA in 10 samples (66.7%) from outbreaks, with one having both VEEV complex and MADV RNAs. VEEV complex RNA was found in five suspected dengue cases from disease surveillance. The rRT-PCR assays identified VEEV complex RNA in three Culex (Melanoconion) vomerifer pools, leading to VEEV isolates in two. Phylogenetic analysis revealed the VEEV ID subtype in positive samples. Notably, 11.9% of dengue-like disease patients showed VEEV infections. Together, our rRT-PCR validation in human and mosquito samples suggests that this method can be incorporated into mosquito and human encephalitic alphavirus surveillance programs in endemic regions.

Mapping Eastern (EEE) and Venezuelan Equine Encephalitides (VEE) among Equines Using Geographical Information Systems, Colombia, 2008-2019.

INTRODUCTION: Eastern equine encephalitis virus (EEEV) and Venezuelan equine encephalitis virus (VEEV) viruses are zoonotic pathogens affecting humans, particularly equines. These neuroarboviruses compromise the central nervous system and can be fatal in different hosts. Both have significantly influenced Colombia; however, few studies analyse its behaviour, and none develop maps using geographic information systems to characterise it. OBJECTIVE: To describe the temporal-spatial distribution of those viruses in Colombia between 2008 and 2019. METHODS: Retrospective cross-sectional descriptive study, based on weekly reports by municipalities of the ICA, of the surveillance of both arboviruses in equines, in Colombia, from 2008 to 2019. The data were converted into databases in Microsoft Access 365®, and multiple epidemiological maps were generated with the Kosmo RC1®3.0 software coupled to shape files of all municipalities in the country. RESULTS: In the study period, 96 cases of EEE and 70 of VEE were reported, with 58% of EEE cases occurring in 2016 and 20% of EEV cases in 2013. The most affected municipalities for EEE corresponded to the department of Casanare: Yopal (20), Aguazul (16), and Tauramena (10). In total, 40 municipalities in the country reported ≥1 case of EEE. CONCLUSIONS: The maps allow a quick appreciation of groups of neighbouring municipalities in different departments (1° political division) and regions of the country affected by those viruses, which helps consider the expansion of the disease associated with mobility and transport of equines between other municipalities, also including international borders, such as is the case with Venezuela. In that country, especially for EEV, municipalities in the department of Cesar are bordering and at risk for that arboviral infection. there is a high risk of equine encephalitis outbreaks, especially for VEE. This poses a risk also, for municipalities in the department of Cesar, bordering with Venezuela.

Endemic and Epidemic Human Alphavirus Infections in Eastern Panama: An Analysis of Population-Based Cross-Sectional Surveys.

Madariaga virus (MADV) has recently been associated with severe human disease in Panama, where the closely related Venezuelan equine encephalitis virus (VEEV) also circulates. In June 2017, a fatal MADV infection was confirmed in a community of Darien Province. We conducted a cross-sectional outbreak investigation with human and mosquito collections in July 2017, where sera were tested for alphavirus antibodies and viral RNA. In addition, by applying a catalytic, force-of-infection (FOI) statistical model to two serosurveys from Darien Province in 2012 and 2017, we investigated whether endemic or epidemic alphavirus transmission occurred historically. In 2017, MADV and VEEV IgM seroprevalences were 1.6% and 4.4%, respectively; IgG antibody prevalences were MADV: 13.2%, VEEV: 16.8%, Una virus (UNAV): 16.0%, and Mayaro virus: 1.1%. Active viral circulation was not detected. Evidence of MADV and UNAV infection was found near households, raising questions about its vectors and enzootic transmission cycles. Insomnia was associated with MADV and VEEV infections, depression symptoms were associated with MADV, and dizziness with VEEV and UNAV. Force-of-infection analyses suggest endemic alphavirus transmission historically, with recent increased human exposure to MADV and VEEV in Aruza and Mercadeo, respectively. The lack of additional neurological cases suggests that severe MADV and VEEV infections occur only rarely. Our results indicate that over the past five decades, alphavirus infections have occurred at low levels in eastern Panama, but that MADV and VEEV infections have recently increased-potentially during the past decade. Endemic infections and outbreaks of MADV and VEEV appear to differ spatially in some locations of eastern Panama.

Venezuelan equine encephalitis virus: the problem is not over for tropical America.

The equine encephalitis viruses, Venezuelan (VEEV), East (EEEV) and West (WEEV), belong to the genus alphavirus, family Togaviridae and still represent a threat for human and animal public health in the Americas. In both, these infections are characterized by high viremia, rash, fever, encephalitis and death. VEEV encephalitis is similar, clinically, to other arboviral diseases, such as dengue, Zika or chikungunya. Most of the alphaviruses are transmitted between vertebrates and mosquitoes. They are able to replicate in a wide number of hosts, including mammals, birds, reptiles, amphibian and arthropods. The VEEV has enzootic and epizootic transmission cycles. At the enzootic one, enzootic strains (subtype I, serotypes D-F and serotypes II-VI) are continuously circulating between mosquitoes and wild rodents in tropical forests and mangroves of the Americas. The main reseroivrs are wild rodent species of the subfamily Sigmodontinae. However, bats can be also accidental reservoirs of VEEV. In this article, we reviewed the main features, epidemiology, clinical aspects and the current perspectives of the VEEV.

An Environmental Niche Model to Estimate the Potential Presence of Venezuelan Equine Encephalitis Virus in Costa Rica.

Venezuelan equine encephalitis virus (VEEV) is an arbovirus transmitted by arthropods, widely distributed in the Americas that, depending on the subtype, can produce outbreaks or yearly cases of encephalitis in horses and humans. The symptoms are similar to those caused by dengue virus and in the worst-case scenario, involve encephalitis, and death. MaxEnt is software that uses climatological, geographical, and occurrence data of a particular species to create a model to estimate possible niches that could have these favorable conditions. We used MaxEnt with a total of 188 registers of VEEV presence, and 20 variables, (19 bioclimatological plus altitude) to determine the niches promising for the presence of VEEV. The area under the ROC curve (AUC) value for the model with all variables was 0.80 for the training data and 0.72 for the test. The variables with the highest contribution to the model were Bio11 (mean temperature of the coldest quarter) 32.5%, Bio17 (precipitation of the driest quarter) 16.9%, Bio2 (annual mean temperature) 15.1%, altitude (m.a.s.l) 6.6%, and Bio18 (precipitation of the warmest quarter) 6.2%. The product of this research will be useful under the one health scheme to animal and human health authorities to forecast areas with high propensity for VEEV cases in the future.

Evolution and spread of Venezuelan equine encephalitis complex alphavirus in the Americas.

Venezuelan equine encephalitis (VEE) complex alphaviruses are important re-emerging arboviruses that cause life-threatening disease in equids during epizootics as well as spillover human infections. We conducted a comprehensive analysis of VEE complex alphaviruses by sequencing the genomes of 94 strains and performing phylogenetic analyses of 130 isolates using complete open reading frames for the nonstructural and structural polyproteins. Our analyses confirmed purifying selection as a major mechanism influencing the evolution of these viruses as well as a confounding factor in molecular clock dating of ancestors. Times to most recent common ancestors (tMRCAs) could be robustly estimated only for the more recently diverged subtypes; the tMRCA of the ID/IAB/IC/II and IE clades of VEE virus (VEEV) were estimated at ca. 149-973 years ago. Evolution of the IE subtype has been characterized by a significant evolutionary shift from the rest of the VEEV complex, with an increase in structural protein substitutions that are unique to this group, possibly reflecting adaptation to its unique enzootic mosquito vector Culex (Melanoconion) taeniopus. Our inferred tree topologies suggest that VEEV is maintained primarily in situ, with only occasional spread to neighboring countries, probably reflecting the limited mobility of rodent hosts and mosquito vectors.

Characterization of Genetic Variability of Venezuelan Equine Encephalitis Viruses.

Venezuelan equine encephalitis virus (VEEV) is a mosquito-borne alphavirus that has caused large outbreaks of severe illness in both horses and humans. New approaches are needed to rapidly infer the origin of a newly discovered VEEV strain, estimate its equine amplification and resultant epidemic potential, and predict human virulence phenotype. We performed whole genome single nucleotide polymorphism (SNP) analysis of all available VEE antigenic complex genomes, verified that a SNP-based phylogeny accurately captured the features of a phylogenetic tree based on multiple sequence alignment, and developed a high resolution genome-wide SNP microarray. We used the microarray to analyze a broad panel of VEEV isolates, found excellent concordance between array- and sequence-based SNP calls, genotyped unsequenced isolates, and placed them on a phylogeny with sequenced genomes. The microarray successfully genotyped VEEV directly from tissue samples of an infected mouse, bypassing the need for viral isolation, culture and genomic sequencing. Finally, we identified genomic variants associated with serotypes and host species, revealing a complex relationship between genotype and phenotype.

How to Assess Data Availability, Accessibility and Format for Risk Analysis?

Risk assessments are mostly carried out based on available data, which do not reflect all data theoretically required by experts to answer them. This study aimed at developing a methodology to assess data availability, accessibility and format, based on a scoring system and focusing on two diseases: Venezuelan equine encephalomyelitis (VEE), still exotic to Europe, and alveolar echinococcosis, caused by Echinococcus multilocularis (EM), endemic in several Member States (MSs). After reviewing 36 opinions of the EFSA-AHAW Panel on risk assessment of animal health questions, a generic list of needed data was elaborated. The methodology consisted, first, in implementing a direct and an indirect survey to collect the data needed for both case studies: the direct survey consisted in a questionnaire sent to contact points of three European MSs (Belgium, France and the Netherlands), and the organization of a workshop gathering experts on both diseases. The indirect survey, focusing on the three MSs involved in the direct survey plus Spain, relied on web searches. Secondly, a scoring system with reference to data availability, accessibility and format was elaborated, to, finally, compare both diseases and data between MSs. The accessibility of data was generally related to their availability. Web searches resulted in more data available for VEE compared to EM, despite its current exotic status in the European Union. Hypertext markup language and portable document files were the main formats of available data. Data availability, accessibility and format should be improved for research scientists/assessors. The format of data plays a key role in the feasibility and rapidness of data management and analysis, through a prompt compilation, combination and aggregation in working databases. Harmonization of data collection process is encouraged, according to standardized procedures, to provide useful and reliable data, both at the national and the international levels for both animal and human health; it would allow assessing data gaps through comparative studies. The present methodology is a good way of assessing the relevance of data for risk assessment, as it allows integrating the uncertainty linked to the quality of data used. Such an approach could be described as transparent and traceable and should be performed systematically.

[Do some conditions contribute to the reemergence of the Venezuelan equine encephalitis virus in the Colombian Alta Guajira?]. / ¿Existen condiciones que favorecen la reaparición del virus de la encefalitis equina venezolana en la Alta Guajira colombiana?

INTRODUCTION: In the last 18 years, epizootics of Venezuelan equine encephalitis have not occurred in places with historic epidemic register (1925-1995) in the Guajira Peninsula, Colombia. OBJECTIVE: To assess if the Guajira Peninsula, Colombia, still maintains the epidemiological conditions for Venezuelan equine encephalitis virus reemergence. MATERIALS AND METHODS: Research was carried out in places affected by the 1995 epidemic. We evaluated: 1) abundance and seasonal variation of vector mosquito populations; 2) availability of mammals that are potential amplifiers of the virus, and 3) knowledge among the community about the disease and its vectors. RESULTS: Most of the 16 mosquito species were found during the rainy season. Aedes taeniorhynchus and Psorophora confinnis showed direct relation with rainfall and temperature. In contrast, the dominant species, Deinocerites atlanticus , was always present in the collections, regardless of climatic conditions. No IgG antibodies were found in humans younger than 17 years old, goats or bovine sera. One third of those interviewed remembered the last epidemic and had basic understanding of the disease. Only 20% of the families were owners of equines, and 8% was informed of the importance of equine vaccination. CONCLUSIONS: Some epidemiological conditions that eventually could help epizootic Venezuelan equine encephalitis virus reemergence are maintained. However, an abrupt decrease in the number of susceptible equines was found in the area. Apparently, this new condition has not allowed the virus reemergence and is the biggest observed change.

Neutralising antibodies for Mayaro virus in Pantanal, Brazil.

The Pantanal hosts diverse wildlife species and therefore is a hotspot for arbovirus studies in South America. A serosurvey for Mayaro virus (MAYV), eastern (EEEV), western (WEEV) and Venezuelan (VEEV) equine encephalitis viruses was conducted with 237 sheep, 87 free-ranging caimans and 748 equids, including 37 collected from a ranch where a neurologic disorder outbreak had been recently reported. Sera were tested for specific viral antibodies using plaque-reduction neutralisation test. From a total of 748 equids, of which 264 were immunised with vaccine composed of EEEV and WEEV and 484 had no history of immunisation, 10 (1.3%) were seropositive for MAYV and two (0.3%) for VEEV using criteria of a ≥ 4-fold antibody titre difference. Among the 484 equids without history of immunisation, 48 (9.9%) were seropositive for EEEV and four (0.8%) for WEEV using the same criteria. Among the sheep, five were sero- positive for equine encephalitis alphaviruses, with one (0.4%) for EEEV, one (0.4%) for WEEV and three (1.3%) for VEEV. Regarding free-ranging caimans, one (1.1%) and three (3.4%), respectively, had low titres for neutralising antibodies to VEEV and undetermined alphaviruses. The neurological disorder outbreak could not be linked to the alphaviruses tested. Our findings represent strong evidence that MAYV and all equine encephalitis alphaviruses circulated in the Pantanal.

¿Existen condiciones que favorecen la reaparición del virus de la encefalitis equina venezolana en la Alta Guajira colombiana? / Do some conditions contribute to the reemergence of the Venezuelan equine encephalitis virus in the Colombian Alta Guajira?

Introducción. En los últimos 18 años, no se han vuelto a registrar epizootias de encefalitis equina venezolana en áreas con antecedentes históricos de epidemia (1925-1995) en la península de La Guajira. Objetivo. Establecer si en la Alta Guajira colombiana se mantienen las condiciones que favorecen la reaparición de las cepas epizoóticas del virus de la encefalitis equina venezolana. Materiales y métodos. La investigación se realizó en las localidades afectadas por la epidemia de 1995, y se evaluaron los siguientes aspectos: 1) abundancia y variación estacional de las poblaciones de los mosquitos vectores; 2) disponibilidad de mamíferos sensibles amplificadores del virus, y 3) conocimiento de los habitantes sobre la enfermedad y sus vectores. Resultados. La mayoría de las especies de mosquitos, incluidas las de los vectores, se encontraron durante la estación lluviosa. Aedes taeniorhynchus y Psorophora confinnis presentaron relación con la precipitación y la temperatura. Deinocerites atlanticus estuvo siempre presente, independientemente de las condiciones climáticas. No se encontraron anticuerpos de tipo IgG en los sueros de humanos menores de 17 años, tampoco en los de los animales caprinos y bovinos analizados. En la encuesta sobre conocimientos, se detectó que la tercera parte de los encuestados recordaba la última epidemia y tenía conocimientos básicos sobre la enfermedad. Solamente 20 % de las familias poseía équidos y el 8 % estaba informado sobre la necesidad de vacunarlos. Conclusiones. Se mantienen algunas condiciones epidemiológicas que eventualmente podrían favorecer la reaparición del virus, pero el número de equinos en riesgo es escaso, lo cual constituye el cambio más notable y lo que, aparentemente, ha impedido la reaparición del virus.

Introduction: In the last 18 years, epizootics of Venezuelan equine encephalitis have not occurred in places with historic epidemic register (1925-1995) in the Guajira Peninsula, Colombia. Objective: To assess if the Guajira Peninsula, Colombia, still maintains the epidemiological conditions for Venezuelan equine encephalitis virus reemergence. Materials and methods: Research was carried out in places affected by the 1995 epidemic. We evaluated: 1) abundance and seasonal variation of vector mosquito populations; 2) availability of mammals that are potential amplifiers of the virus, and 3) knowledge among the community about the disease and its vectors. Results: Most of the 16 mosquito species were found during the rainy season. Aedes taeniorhynchus and Psorophora confinnis showed direct relation with rainfall and temperature. In contrast, the dominant species, Deinocerites atlanticus , was always present in the collections, regardless of climatic conditions. No IgG antibodies were found in humans younger than 17 years old, goats or bovine sera. One third of those interviewed remembered the last epidemic and had basic understanding of the disease. Only 20% of the families were owners of equines, and 8% was informed of the importance of equine vaccination. Conclusions: Some epidemiological conditions that eventually could help epizootic Venezuelan equine encephalitis virus reemergence are maintained. However, an abrupt decrease in the number of susceptible equines was found in the area. Apparently, this new condition has not allowed the virus reemergence and is the biggest observed change.

Genetic and evolutionary characterization of Venezuelan equine encephalitis virus isolates from Argentina.

Venezuelan equine encephalitis viruses (VEEV) are emerging pathogens of medical and veterinary importance circulating in America. Argentina is a country free from epizootic VEEV activity, with circulation of enzootic strains belonging to Rio Negro virus (RNV; VEEV subtype VI) and Pixuna virus (PIXV, VEEV subtype IV). In this work, we aim to report the sequencing and phylogenetic analyses of all Argentinean VEE viruses, including 7 strains previously isolated from mosquitoes in 1980, 5 sequences obtained from rodents in 1991 and 11 sequences amplified from mosquitoes between 2003 and 2005. Two genomic regions, corresponding to the non-structural protein 4 (nsP4) and the protein E3/E2 (PE2) genes were analyzed, but only 8 samples could be amplified in the last one (longer and more variable fragment of 702 bp). For both genomic fragments, phylogenetic trees showed the absence of lineages within RNV group, and a close genetic relationship between Argentinean strains and the prototype strain BeAr35645 for PIXV clade. The analysis of nsP4 gene opens the possibility to propose a possible geographic clustering of strains within PIXV group (Argentina and Brazil). Coalescent analysis performed on RNV sequences suggested a common ancestor of 58.3 years (with a 95% highest posterior density [HPD] interval of 16.4-345.7) prior to 1991 and inferred a substitution rate of 9.8×10(-5)substitutions/site/year, slightly lower than other enzootic VEE viruses. These results provide, for the first time, information about genetic features and variability of all VEEVs detected in Argentina, creating a database that will be useful for future detections in our country. This is particularly important for RNV, which has indigenous circulation.

Venezuelan equine encephalitis viruses (VEEV) in Argentina: serological evidence of human infection.

Venezuelan equine encephalitis viruses (VEEV) are responsible for human diseases in the Americas, producing severe or mild illness with symptoms indistinguishable from dengue and other arboviral diseases. For this reason, many cases remain without certain diagnosis. Seroprevalence studies for VEEV subtypes IAB, ID, IF (Mosso das Pedras virus; MDPV), IV (Pixuna virus; PIXV) and VI (Rio Negro virus; RNV) were conducted in persons from Northern provinces of Argentina: Salta, Chaco and Corrientes, using plaque reduction neutralization test (PRNT). RNV was detected in all studied provinces. Chaco presented the highest prevalence of this virus (14.1%). Antibodies against VEEV IAB and -for the first time- against MDPV and PIXV were also detected in Chaco province. In Corrientes, seroprevalence against RNV was 1.3% in the pediatric population, indicating recent infections. In Salta, this was the first investigation of VEEV members, and antibodies against RNV and PIXV were detected. These results provide evidence of circulation of many VEE viruses in Northern Argentina, showing that surveillance of these infectious agents should be intensified.

Mosquito-host interactions during and after an outbreak of equine viral encephalitis in Eastern Panama.

Mosquito blood meals provide information about the feeding habits and host preference of potential arthropod-borne disease vectors. Although mosquito-borne diseases are ubiquitous in the Neotropics, few studies in this region have assessed patterns of mosquito-host interactions, especially during actual disease outbreaks. Based on collections made during and after an outbreak of equine viral encephalitis, we identified the source of 338 blood meals from 10 species of mosquitoes from Aruza Abajo, a location in Darien province in eastern Panama. A PCR based method targeting three distinct mitochondrial targets and subsequent DNA sequencing was used in an effort to delineate vector-host relationships. At Aruza Abajo, large domesticated mammals dominated the assemblage of mosquito blood meals while wild bird and mammal species represented only a small portion of the blood meal pool. Most mosquito species fed on a variety of hosts; foraging index analysis indicates that eight of nine mosquito species utilize hosts at similar proportions while a stochastic model suggests dietary overlap among species was greater than would be expected by chance. The results from our null-model analysis of mosquito diet overlap are consistent with the hypothesis that in landscapes where large domestic animals dominate the local biomass, many mosquito species show little host specificity, and feed upon hosts in proportion to their biomass, which may have implications for the role of livestocking patterns in vector-borne disease ecology.

Eastern equine encephalitis in Latin America.

BACKGROUND: The eastern equine encephalitis (EEE) and Venezuelan equine encephalitis (VEE) viruses are pathogens that infect humans and horses in the Americas. Outbreaks of neurologic disease in humans and horses were reported in Panama from May through early August 2010. METHODS: We performed antibody assays and tests to detect viral RNA and isolate the viruses in serum samples from hospitalized patients. Additional cases were identified with enhanced surveillance. RESULTS: A total of 19 patients were hospitalized for encephalitis. Among them, 7 had confirmed EEE, 3 had VEE, and 1 was infected with both viruses; 3 patients died, 1 of whom had confirmed VEE. The clinical findings for patients with EEE included brain lesions, seizures that evolved to status epilepticus, and neurologic sequelae. An additional 99 suspected or probable cases of alphavirus infection were detected during active surveillance. In total, 13 cases were confirmed as EEE, along with 11 cases of VEE and 1 case of dual infection. A total of 50 cases in horses were confirmed as EEE and 8 as VEE; mixed etiologic factors were associated with 11 cases in horses. Phylogenetic analyses of isolates from 2 cases of equine infection with the EEE virus and 1 case of human infection with the VEE virus indicated that the viruses were of enzootic lineages previously identified in Panama rather than new introductions. CONCLUSIONS: Cases of EEE in humans in Latin America may be the result of ecologic changes that increased human contact with enzootic transmission cycles, genetic changes in EEE viral strains that resulted in increased human virulence, or an altered host range. (Funded by the National Institutes of Health and the Secretaría Nacional de Ciencia, Tecnología e Innovación, Panama.).

Venezuelan equine encephalitis virus activity in the Gulf Coast region of Mexico, 2003-2010.

Venezuelan equine encephalitis virus (VEEV) has been the causative agent for sporadic epidemics and equine epizootics throughout the Americas since the 1930s. In 1969, an outbreak of Venezuelan equine encephalitis (VEE) spread rapidly from Guatemala and through the Gulf Coast region of Mexico, reaching Texas in 1971. Since this outbreak, there have been very few studies to determine the northward extent of endemic VEEV in this region. This study reports the findings of serologic surveillance in the Gulf Coast region of Mexico from 2003-2010. Phylogenetic analysis was also performed on viral isolates from this region to determine whether there have been substantial genetic changes in VEEV since the 1960s. Based on the findings of this study, the Gulf Coast lineage of subtype IE VEEV continues to actively circulate in this region of Mexico and appears to be responsible for infection of humans and animals throughout this region, including the northern State of Tamaulipas, which borders Texas.

First detection of Rio Negro virus (Venezuelan equine encephalitis complex subtype VI) in Córdoba, Argentina.

Rio Negro virus (RNV) (Venezuelan equine encephalitis subtype VI) circulates only in Argentina; in northern provinces, isolates have been obtained from mosquitoes and rodents since 1980 and have been associated with acute febrile illness in humans. However, no studies of RNV have been performed in the central area of the country. We carried out molecular and serological detection of RNV in Córdoba, a province of the central part of the country, in mosquitoes and humans, respectively. One mosquito pool tested positive for alphavirus RNA by reverse transcriptase-nested polymerase chain reaction (RT-nested PCR). Subsequent sequencing determined that this alphavirus grouped with RNV. Serological studies detected antibodies to RNV in one human serum sample, which was obtained during the same period that RNV was detected using the aforementioned molecular methods. This is the first report of RNV circulation in the central area of Argentina, indicating an expansion of its original distribution. These results highlight the importance of strengthening surveillance procedures in endemic areas, as well as in new regions where RNV may emerge.

First detection of Rio Negro virus (Venezuelan equine encephalitis complex subtype VI) in Córdoba, Argentina

Rio Negro virus (RNV) (Venezuelan equine encephalitis subtype VI) circulates only in Argentina; in northern provinces, isolates have been obtained from mosquitoes and rodents since 1980 and have been associated with acute febrile illness in humans. However, no studies of RNV have been performed in the central area of the country. We carried out molecular and serological detection of RNV in Córdoba, a province of the central part of the country, in mosquitoes and humans, respectively. One mosquito pool tested positive for alphavirus RNA by reverse transcriptase-nested polymerase chain reaction (RT-nested PCR). Subsequent sequencing determined that this alphavirus grouped with RNV. Serological studies detected antibodies to RNV in one human serum sample, which was obtained during the same period that RNV was detected using the aforementioned molecular methods. This is the first report of RNV circulation in the central area of Argentina, indicating an expansion of its original distribution. These results highlight the importance of strengthening surveillance procedures in endemic areas, as well as in new regions where RNV may emerge.

The crab hole mosquito blues.

Venezuelan equine encephalomyelitis (VEE) epizoodemics were reported at 6-10-year intervals in northern South America beginning in the 1920s. In 1937, epizootic VEE virus was isolated from infected horse brain and shown as distinct from the North American equine encephalomyelitis viruses. Subsequently, epizootic and sylvatic strains were isolated in distinct ecosystems; isolates were characterized serologically as epizootic subtype I, variants A/B and C; or sylvatic (enzootic) subtype I, variants D, E, and F, and subtypes II, III, and IV. In 1969, variant I-A/B virus was transported from a major outbreak in northern South America to the borders of El Salvador, Guatemala, and Honduras. This musical poem describes the history and ecology of VEE viruses and the epidemiology of an unprecedented 1969 movement of VEE viruses from South America to equids and humans in Central America from Costa Rica to Guatemala and Belize and in Mexico and the United States that continued until 1972.

Venezuelan equine encephalitis in Panama: fatal endemic disease and genetic diversity of etiologic viral strains.

Venezuelan equine encephalitis (VEE) is a reemerging, mosquito-borne viral disease of the neotropics that is severely debilitating and sometimes fatal to humans. Periodic epidemics mediated by equine amplification have been recognized since the 1920s, but interepidemic disease is rarely recognized. We report here clinical findings and genetic characterization of 42 cases of endemic VEE detected in Panama from 1961-2004. Recent clusters of cases occurred in Darien (eastern Panama) and Panama provinces (central Panama) near rainforest and swamp habitats. Patients ranged from 10 months to 48 years of age, and the more severe cases with neurological complications, including one fatal infection, were observed in children. The VEE virus strains isolated from these cases all belonged to an enzootic, subtype ID lineage known to circulate among sylvatic vectors and rodent reservoir hosts in Panama and Peru. These findings underscore endemic VEE as an important but usually neglected arboviral disease of Latin America.