Chikungunya virus infections among travellers returning to Spain, 2008 to 2014.

Since the first documented autochthonous transmission of chikungunya virus in the Caribbean island of Saint Martin in 2013, the infection has been reported within the Caribbean region as well as North, Central and South America. The risk of autochthonous transmission of chikungunya virus becoming established in Spain may be elevated due to the large numbers of travellers returning to Spain from countries affected by the 2013 epidemic in the Caribbean and South America, as well as the existence of the Aedes albopictus vector in certain parts of Spain. We retrospectively analysed the laboratory diagnostic database of the National Centre for Microbiology, Institute of Health Carlos III (CNM-ISCIII) from 2008 to 2014. During the study period, 264 confirmed cases, of 1,371 suspected cases, were diagnosed at the CNM-ISCIII. In 2014 alone, there were 234 confirmed cases. The highest number of confirmed cases were reported from the Dominican Republic (n = 136), Venezuela (n = 30) and Haiti (n = 11). Six cases were viraemic in areas of Spain where the vector is present. This report highlights the need for integrated active case and vector surveillance in Spain and other parts of Europe where chikungunya virus may be introduced by returning travellers.

Concurrent Infection With Dengue Type 4 and Plasmodium falciparum Acquired in Haiti.

We report one laboratory-confirmed coinfection by dengue type 4 and Plasmodium falciparum imported to Spain from Haiti. Diagnosis was made by real-time polymerase chain reaction (RT-PCR), serology, quantitative buffy coat, and thick blood smear. In areas where both infections are present, diagnosis of both diseases should be considered because a delay in the treatment of malaria could be fatal.

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.

Desarrollo de un método de transcripción inversa seguida de reacción en cadena de la polimerasa para la detección del virus de la fiebre amarilla / Development of a reverse transcription polymerase chain reaction method for yellow fever virus detection

Introduction. Yellow fever is considered a re-emerging disease and is endemic in tropical regions of Africa and South America. At present, there are no standardized or commercialized kits available for yellow fever virus detection. Therefore, diagnosis must be made by time-consuming routine techniques, and sometimes, the virus or its proteins are not detected. Furthermore, co-circulation with other flaviviruses, including dengue virus, increases the difficulty of diagnosis. Objective. To develop a specific reverse transcriptase-polymerase chain reaction (RT-PCR) and nested PCR-based assay to improve the detection and diagnosis of yellow fever virus using both serum and fresh tissue samples. Materials and methods. RT-PCR primers were designed to amplify a short fragment of all yellow fever virus genotypes reported. A second set of primers was used in a nested PCR to increase sensitivity. Thirty-three clinical samples were tested with the standardized reaction. Results. The expected amplicon was obtained in 25 out of 33 samples analyzed using this approach, and 2 more samples tested positive after a subsequent nested PCR approach. Conclusion. This improved technique not only ensures the specific detection of a wide range of yellow fever virus genotypes but also may increase the sensitivity of detection by introducing a second round of amplification, allowing a rapid differential diagnosis between dengue and yellow fever infection, which is required for effective surveillance and opportune epidemiologic measures.

Introducción. La fiebre amarilla se considera una enfermedad reemergente y endémica en regiones tropicales de África y Suramérica. Actualmente, no existen estuches estandarizados o comerciales disponibles para la detección del virus de la fiebre amarilla y, por lo tanto, el diagnóstico debe hacerse mediante técnicas de rutina que consumen mucho tiempo y algunas veces no garantizan la detección del virus o de sus proteínas. Además, la cocirculación con otros flavivirus, incluyendo el del dengue, hacen el diagnóstico más complicado. Objetivo. Desarrollar un ensayo específico de amplificación basado en transcripción inversa seguida de reacción en cadena de la polimerasa, con el fin de mejorar la detección y el diagnóstico de la fiebre amarilla, tanto a partir de suero como de tejido fresco. Materiales y métodos. Se diseñaron iniciadores específicos para amplificar un fragmento conservado del virus de la fiebre amarilla. Un segundo par de iniciadores se usó en una reacción de amplificación anidada para incrementar la sensibilidad. Se probaron 33 muestras clínicas con la técnica estandarizada. Resultados. El amplímero esperado se obtuvo en 25 de las 33 muestras analizadas usando este método y 2 más resultaron positivas después de la reacción anidada. Conclusión. Esta técnica mejorada garantiza la detección de todos los genotipos virales de fiebre amarilla y puede incrementar la sensibilidad del ensayo introduciendo una segunda etapa de amplificación, lo cual permite el diagnóstico diferencial con infección por dengue y otros flavivirus, lo cual es de gran importancia para la vigilancia y la toma de medidas epidemiológicas oportunas.

Development of a reverse transcription polymerase chain reaction method for yellow fever virus detection.

INTRODUCTION: Yellow fever is considered a re-emerging disease and is endemic in tropical regions of Africa and South America. At present, there are no standardized or commercialized kits available for yellow fever virus detection. Therefore, diagnosis must be made by time-consuming routine techniques, and sometimes, the virus or its proteins are not detected. Furthermore, co-circulation with other flaviviruses, including dengue virus, increases the difficulty of diagnosis. OBJECTIVE: To develop a specific reverse transcriptase-polymerase chain reaction (RT-PCR) and nested PCR-based assay to improve the detection and diagnosis of yellow fever virus using both serum and fresh tissue samples. MATERIALS AND METHODS: RT-PCR primers were designed to amplify a short fragment of all yellow fever virus genotypes reported. A second set of primers was used in a nested PCR to increase sensitivity. Thirty-three clinical samples were tested with the standardized reaction. RESULTS: The expected amplicon was obtained in 25 out of 33 samples analyzed using this approach, and 2 more samples tested positive after a subsequent nested PCR approach. CONCLUSION: This improved technique not only ensures the specific detection of a wide range of yellow fever virus genotypes but also may increase the sensitivity of detection by introducing a second round of amplification, allowing a rapid differential diagnosis between dengue and yellow fever infection, which is required for effective surveillance and opportune epidemiologic measures.

Epidemiología molecular de los virus Dengue / Molecular epidemiology of Dengue virus

El dengue es la enfermedad viral más importante transmitida por mosquitos a humanos por su alta morbimortalidad y el potencial de diseminación de su vector Aedes aegypti. Además, la falta de una vacuna y medicamentos antivirales específicos, así como el incremento progresivo de las infecciones secundarias y la hiperendemicidad en diferentes países, hacen de esta enfermedad un problema de salud pública. Existen cuatro serotipos del virus del dengue (DENV), dentro de cada serotipo se han descrito varios genotipos, constituidos a su vez por diferentes linajes o clados. La epidemiología molecular combina los análisis filogenéticos de los DENV detectados en un área geográfica, en un tiempo definido, con la información clínica y epidemiológica disponible. El objetivo de estos estudios es tratar de establecer asociaciones entre genotipos o linajes virales con el origen (ancestros), procedencia geográfica, ruta de transmisión viral, severidad de la enfermedad, grupos poblacionales afectados, y la intensidad y extensión de los brotes epidémicos. La epidemiología molecular ha generado información relevante como la etiología del DENV genotipo Asiático en los casos graves de dengue de la epidemia ocurrida en Venezuela en 1989, y la identificación de cambios nucleotídicos puntuales en el genoma viral asociados a propiedades biológicas fundamentales. En la actualidad se hace necesario realizar análisis exhaustivos del genoma viral completo, conjuntamente con el análisis bioinformático, biológico, clínico y epidemiológico de los cuatro serotipos circulantes en los países endémicos, así como instaurar en los laboratorios adscritos a los sistemas de vigilancia epidemiológica del dengue, la vigilancia molecular para la identificación de genotipos (o linajes) circulantes, lo que contribuiría entre otros aspectos al control efectivo de la enfermedad por DENV.

Dengue is the most important viral disease transmitted by mosquitoes to humans in tropical and subtropical regions of the world. This is the result of its high morbidity and mortality, the spread potential of the vector Aedes aegypti, the lack of effective vaccines and specific antiviral drugs, the gradual increase in secondary infections and hyperendemicity differences in distinct countries. There are four serotypes of dengue virus which are phylogenetically grouped in genotypes and subdivided in lineages or clades. Molecular epidemiology combines phylogenetic analysis of DENV detected in particular geographic areas within a defined time with the available clinical and epidemiologic information. The objective of these studies is to look for relationships between genotypes or lineages, viral origin, geographical spreading and routes of viral transmission, disease severity, population groups affected, and the intensity, speed and extent of outbreaks. Also, molecular epidemiology has generated relevant information such as the Asian genotype DENV etiology in cases of the severe dengue epidemic in Venezuela in 1989, and the identification of specific nucleotide changes in the viral genome associated with its fundamental biological properties. However, analysis of the complete viral genome, together with bioinformatic, biological, clinical and epidemiological analysis corresponding to the four serotypes circulating in endemic countries should be performed. Molecular surveillance for the identification of genotypes (or strains) circulating should be implemented in the laboratories responsible for the epidemiological surveillance of dengue, which would improve the effective control of DENV.

Specific detection of all members of the Venezuelan Equine Encephalitis complex: development of a RT-Nested PCR.

Venezuelan Equine Encephalitis (VEE) complex belongs to alphavirus genus in the family Togaviridae. Several species of this complex are pathogenic to humans. VEE infections can produce severe or mild disease, and many cases remain undiagnosed. A specific and sensitive reverse transcriptase nested polymerase chain reaction (RT-Nested PCR) method was developed for the detection of all VEE subtypes, including Rio Negro Virus (RNV) (subtype VI), which circulates only in Argentina. Degenerated primers were designed and thermal cycling parameters were standardized. This technique is suitable for rapid and specific detection of these viruses, and may be useful for diagnosis and surveillance.

Phylogenetic reconstruction of dengue virus type 2 in Colombia.

BACKGROUND: Dengue fever is perhaps the most important viral re-emergent disease especially in tropical and sub-tropical countries, affecting about 50 million people around the world yearly. In Colombia, dengue virus was first detected in 1971 and still remains as a major public health issue. Although four viral serotypes have been recurrently identified, dengue virus type 2 (DENV-2) has been involved in the most important outbreaks during the last 20 years, including 2010 when the fatality rate highly increased. As there are no major studies reviewing virus origin and genotype distribution in this country, the present study attempts to reconstruct the phylogenetic history of DENV-2 using a sequence analysis from a 224 bp PCR-amplified product corresponding to the carboxyl terminus of the envelope (E) gene from 48 Colombian isolates. RESULTS: As expected, the oldest isolates belonged to the American genotype (subtype V), but the strains collected since 1990 represent the American/Asian genotype (subtype IIIb) as previously reported in different American countries. Interestingly, the introduction of this genotype coincides with the first report of dengue hemorrhagic fever in Colombia at the end of 1989 and the increase of cases during the next years. CONCLUSION: After replacement of the American genotype, several lineages of American/Asian subtype have rapidly spread all over the country evolving in new clades. Nevertheless, the direct association of these new variants in the raise of lethality rate observed during the last outbreak has to be demonstrated.

Silent circulation of St. Louis encephalitis virus prior to an encephalitis outbreak in Cordoba, Argentina (2005).

St. Louis encephalitis virus is a complex zoonoses. In 2005, 47 laboratory-confirmed and probable clinical cases of SLEV infection were reported in Córdoba, Argentina. Although the causes of 2005 outbreak remain unknown, they might be related not only to virological factors, but also to ecological and environmental conditions. We hypothesized that one of the factors for SLE reemergence in Córdoba, Argentina, was the introduction of a new SLEV genotype (SLEV genotype III), with no previous activity in the area. In order to evaluate this hypothesis we carried out a molecular characterization of SLEV detections from mosquitoes collected between 2001 and 2004 in Córdoba city. A total of 315 mosquito pools (11,002 individuals) including 12 mosquitoes species were analyzed. Overall, 20 pools (8 mosquitoes species) were positive for SLEV. During this study, genotypes II, V and VII were detected. No mosquito pool infected with genotype III was detected before the 2005 outbreak. Genotype V was found every year and in the 8 sampled sites. Genotypes II and VII showed limited temporal and spatial activities. We cannot dismiss the association of genotype II and V as etiological agents during the outbreak. However, the silent circulation of other SLEV strains in Córdoba city before the 2005 outbreak suggests that the introduction of genotype III was an important factor associated to this event. Not mutually exclusive, other factors such as changes in avian hosts and mosquitoes vectors communities, driven by climatic and environmental modifications, should also be taken into consideration in further studies.

Quantum phase transitions in alternating spin-(1/2, 5/2) Heisenberg chains.

The ground state spin-wave excitations and thermodynamic properties of two types of ferrimagnetic chains are investigated: the alternating spin-1/2 spin-5/2 chain and a similar chain with a spin-1/2 pendant attached to the spin-5/2 site. Results for magnetic susceptibility, magnetization and specific heat are obtained through the finite-temperature Lanczos method with the aim of describing the available experimental data, as well as comparison with theoretical results from the semiclassical approximation and the low-temperature susceptibility expansion derived from Takahashi's modified spin-wave theory. In particular, we study in detail the temperature versus magnetic field phase diagram of the spin-1/2 spin-5/2 chain, in which several low-temperature quantum phases are identified: the Luttinger liquid phase, the ferrimagnetic plateau and the fully polarized phase, and the respective quantum critical points and crossover lines.

Viral diversity of Junín virus field strains.

The Argentine Hemorrhagic Fever, an endemic disease present in a much of Argentina, is caused by the Junín virus (JUNV). Currently, there are sequences available from several strains of this virus, like those belonging to the vaccine lineage (XJ13, XJ#44 and Candid#1), as well as MC2 (rodent isolate) and IV4454 (human isolate). In this article, we report sequence information on two fragments of genomic segment S of viral isolates from the endemic area. A Nested-RT-PCR was used to amplify discrete genomic regions of 13 isolates of rodent and human origin. The bioinformatics studies revealed a great homogeneity of sequences among the JUNV isolates. The phylogenetic classification showed greater evolutionary distance between the old world arenaviruses (Lassa and LCM virus) than between the new world arenaviruses (JUNV and Machupo virus).

Granada virus: a natural phlebovirus reassortant of the sandfly fever Naples serocomplex with low seroprevalence in humans.

A new member of the phlebovirus genus, tentatively named Granada virus, was detected in sandflies collected in Spain. By showing the presence of specific neutralizing antibodies in human serum collected in Granada, we show that Granada virus infects humans. The analysis of the complete genome of Granada virus revealed that this agent is likely to be a natural reassortant of the recently described Massilia virus (donor of the long and short segments) with a yet unidentified phlebovirus (donor of the medium segment).

Phylogenetic history demonstrates two different lineages of dengue type 1 virus in Colombia.

BACKGROUND: Dengue Fever is one of the most important viral re-emergent diseases affecting about 50 million people around the world especially in tropical and sub-tropical countries. In Colombia, the virus was first detected in the earliest 70's when the disease became a major public health concern. Since then, all four serotypes of the virus have been reported. Although most of the huge outbreaks reported in this country have involved dengue virus serotype 1 (DENV-1), there are not studies about its origin, genetic diversity and distribution. RESULTS: We used 224 bp corresponding to the carboxyl terminus of envelope (E) gene from 74 Colombian isolates in order to reconstruct phylogenetic relationships and to estimate time divergences. Analyzed DENV-1 Colombian isolates belonged to the formerly defined genotype V. Only one virus isolate was clasified in the genotype I, likely representing a sole introduction that did not spread. The oldest strains were closely related to those detected for the first time in America in 1977 from the Caribbean and were detected for two years until their disappearance about six years later. Around 1987, a split up generated 2 lineages that have been evolving separately, although not major amino acid changes in the analyzed region were found. CONCLUSION: DENV-1 has been circulating since 1978 in Colombia. Yet, the phylogenetic relationships between strains isolated along the covered period of time suggests that viral strains detected in some years, although belonging to the same genotype V, have different recent origins corresponding to multiple re-introduction events of viral strains that were circulating in neighbor countries. Viral strains used in the present study did not form a monophyletic group, which is evidence of a polyphyletic origin. We report the rapid spread patterns and high evolution rate of the different DENV-1 lineages.

Enzootic activity of pixuna and Rio Negro viruses (Venezuelan equine encephalitis complex) in a neotropical region of Argentina.

Venezuelan Equine Encephalitis complex viruses cause epidemics and epizootics periodically in some regions of the Americas. In Argentina, only enzootic Rio Negro virus (AG80-663) (RNV) has been isolated. To survey and identify activity of viruses that belong to Venezuelan Equine Encephalitis complex in a template region of the country, a generic Alphavirus RT-Nested PCR was performed in 99 mosquito pools collected in Chaco province. Five pools were positive, and amplicons were sequenced: four of them clustered with RNV(AG80-663) and one with Pixuna virus. This is the first report of the circulation of Pixuna virus in Argentina, and it confirms enzootic and endemic activity of RNV(AG80-663) in neotropical regions of this country.

Simultaneous circulation of genotypes I and III of dengue virus 3 in Colombia.

BACKGROUND: Dengue is a major health problem in tropical and subtropical regions. In Colombia, dengue viruses (DENV) cause about 50,000 cases annually, 10% of which involve Dengue Haemorrhagic Fever/Dengue Shock Syndrome. The picture is similar in other surrounding countries in the Americas, with recent outbreaks of severe disease, mostly associated with DENV serotype 3, strains of the Indian genotype, introduced into the Americas in 1994. RESULTS: The analysis of the 3'end (224 bp) of the envelope gene from 32 DENV-3 strains recently recovered in Colombia confirms the circulation of the Indian genotype, and surprisingly the co-circulation of an Asian-Pacific genotype only recently described in the Americas. CONCLUSION: These results have important implications for epidemiology and surveillance of DENV infection in Central and South America. Molecular surveillance of the DENV genotypes infecting humans could be a very valuable tool for controlling/mitigating the impact of the DENV infection.

Reliable detection of St. Louis encephalitis virus by RT-nested PCR.

INTRODUCTION: St. Louis encephalitis virus (SLEV) is a re-emerging arbovirus in South America, with reported cases in humans in Argentina and Brazil. This fact indicates that there is an urgent need to increase the current knowledge about this virus in order to control and prevent future cases. Exhaustive epidemiological and laboratory investigation is required to ensure fast, accurate identification of the viral agent and allow prompt surveillance action by health authorities. Herein, we report the development of a species-specific RT-nested PCR to detect SLEV. MATERIAL AND METHODS: After selecting the SLEV genomic region providing the greatest information on the natural genetic variability of this virus, degenerated oligonucleotide primers were designed to amplify a 234-bp fragment of the envelope gene from nine SLEV strains (Parton, BeH356964, SPAN11916, AN9275, AN9124, 78V6507 and 3 SLEV strains obtained from naturally infected mosquito pools). RESULTS: The method was able to identify the genome of all the SLEV strains tested and did not amplify unrelated RNA viruses, such as yellow fever virus, Ilheus virus, dengue-2 virus, Bussuquara virus, West Nile virus, Japanese encephalitis virus and Murray Valley encephalitis virus. The method was specific and sensitive, with a lower detection limit of < 10 plaque-forming units. CONCLUSION: This molecular assay is a reliable procedure with a wide spectrum for detecting the natural diversity of SLEV and may be useful for ecological studies, clinical and laboratory settings and virological surveillance.

Genotype III Saint Louis encephalitis virus outbreak, Argentina, 2005.

Twenty-six years after it was last detected, Saint Louis encephalitis virus (SLEV) genotype III reemerged in 2005 in C6rdoba, Argentina, where it caused an outbreak. Two genotype III SLEV strains were isolated from Culex quinquefasciatus. A 71.43% prevalence for neutralizing antibodies was found in domestic fowl in the homestead of a patient with encephalitis.

[Analysis of an outbreak of viral meningitis in the province of Tucuman, Argentina]. / Análisis de un brote de meningitis viral en la provincia de Tucumán, Argentina.

OBJECTIVE: To confirm the occurrence of an outbreak of viral meningitis in 1996 in the province of Tucuman, Argentina, and to study the outbreak's epidemiological characteristics. METHODS: We analyzed information from the National Epidemiological Surveillance System of the Ministry of Health (MOH) of Argentina for 1994-1998 that had been provided by the MOH's Bureau of Epidemiology. We calculated incidence rates using population estimates for the years 1994-1998 developed by the National Statistics and Census Institute, based on the 1991 census. We studied frequencies with contingency tables, using the chi-square method with Yates' correction. Results were considered significant when P < 0.05. RESULTS: We confirmed the occurrence of an outbreak of 189 cases of viral meningitis between 11 February and 18 May 1996. The incidence of cases in Tucuman province increased between 1995 and 1996, from 0.5 to 19.3 cases per 100 000 person-years. That 1996 rate in Tucuman was significantly higher than what was seen in the rest of the country (2.8 cases per 100 000 person-years). Of the 189 cases, 142 of them (75.1%) occurred in children less than 9 years old. Out of 111 samples studied, 65 of them (58.6%) were enterovirus-positive. Through reverse transcription-nested polymerase chain reaction, enteroviruses were found in 66.3% (53/80) of the cases studied by this method, versus in only 29.6% (24/81) of the cases studied through viral isolation. In the 22 samples that were serotyped, echovirus type 4 was identified in 15 of them (68%): 5 by isolation, 3 by sequencing, and 7 by both methods. During the Tucuman outbreak, at least 56% of the cases were hospitalized. This viral meningitis outbreak shows the capacity of enteroviruses to spread and cause disease. CONCLUSIONS: The use of molecular methods makes it possible to rapidly diagnose the etiological virus and to better control an outbreak. Recognizing this outbreak in Tucuman sooner could have averted the majority of the hospitalizations and the indiscriminate use of antibiotics.

Análisis de un brote de meningitis viral en la provincia de Tucumán, Argentina / Analysis of an outbreak of viral meningitis in the province of Tucuman, Argentina

OBJETIVO: Confirmar la existencia de un brote de meningitis viral en 1996 en la provincia de Tucumán, Argentina, y estudiar sus características epidemiológicas. MÉTODOS: Se analizó información obtenida del Sistema Nacional de Vigilancia Epidemiológica (SINAVE) del Ministerio de Salud de Argentina para el período de 1994-1998, la cual fue provista por la Dirección de Epidemiología de dicho ministerio. Para el cálculo de incidencias se usaron estimaciones poblacionales para los años 1994-1998 realizadas por el Instituto Nacional de Estadística y Censos (INDEC) sobre la base del censo de 1991. El estudio de frecuencias se realizó mediante el análisis de tablas de contingencia de doble entrada, según el método de ji cuadrado con la corrección de Yates. Se consideró significativo el resultado cuando P < 0,05. RESULTADOS: Se confirmó la presencia de un brote de 189 casos entre el 11 de febrero y el 18 de mayo de 1996. La incidencia de casos en la provincia mostró un aumento entre 1995 y 1996 (de 0,5 a 19,3 casos por 100000 años-persona) y dicha incidencia fue significativamenrte mayor que la observada en el resto del país (19,3 frente a 2,8 casos por 100000 años-persona). El 75,1 por ciento de los casos ocurrió en niños menores de 9 años (142/189). Se detectó la presencia de Enterovirus (EV) en 65 de las 111 muestras estudiadas (58,6 por ciento). Mediante la reacción en cadena de la polimerasa (RCP) anidada con transcripción inversa se logró detectar EV en 66,3 por ciento (53/80) de los casos estudiados por este método, en comparación con solo 29,6 por ciento (24/81) de los estudiados mediante aislamiento viral. Se identificó echovirus tipo 4 en 15 (68 por ciento) en las 22 muestras tipificadas (5 por aislamiento, 3 por secuenciación y 7 por ambos métodos). Este brote demuestra la capacidad de los EV para diseminarse y producir enfermedad en la población. Durante el brote, por lo menos 56 por ciento de los casos fueron hospitalizados. CONCLUSIONES: El uso de métodos moleculares permitió el diagnóstico rápido del virus etiológico y posibilitó un mejor control del brote. El reconocimiento temprano de este podría haber evitado la mayoría de las hospitalizaciones y el uso indiscriminado de antibióticos

Objective. To confirm the occurrence of an outbreak of viral meningitis in 1996 in the province of Tucuman, Argentina, and to study the outbreak's epidemiological characteristics. Methods. We analyzed information from the National Epidemiological Surveillance System of the Ministry of Health (MOH) of Argentina for 1994­1998 that had been provided by the MOH's Bureau of Epidemiology. We calculated incidence rates using population estimates for the years 1994­1998 developed by the National Statistics and Census Institute, based on the 1991 census. We studied frequencies with contingency tables, using the chi-square method with Yates' correction. Results were considered significant when P < 0.05. Results. We confirmed the occurrence of an outbreak of 189 cases of viral meningitis between 11 February and 18 May 1996. The incidence of cases in Tucuman province increased between 1995 and 1996, from 0.5 to 19.3 cases per 100 000 person-years. That 1996 rate in Tucuman was significantly higher than what was seen in the rest of the country (2.8 cases per 100 000 person-years). Of the 189 cases, 142 of them (75.1%) occurred in children less than 9 years old. Out of 111 samples studied, 65 of them (58.6%) were enterovirus-positive. Through reverse transcription-nested polymerase chain reaction, enteroviruses were found in 66.3% (53/80) of the cases studied by this method, versus in only 29.6% (24/81) of the cases studied through viral isolation. In the 22 samples that were serotyped, echovirus type 4 was identified in 15 of them (68%): 5 by isolation, 3 by sequencing, and 7 by both methods. During the Tucuman outbreak, at least 56% of the cases were hospitalized. This viral meningitis outbreak shows the capacity of enteroviruses to spread and cause disease. Conclusions. The use of molecular methods makes it possible to rapidly diagnose the etiological virus and to better control an outbreak. Recognizing this outbreak in Tucuman sooner could have averted the majority of the hospitalizations and the indiscriminate use of antibiotics.