Tracing the evolution of the chikungunya virus in Argentina, 2016-2023: independent introductions and prominence of Latin American lineages.

Chikungunya virus (CHIKV) has emerged as a significant public health concern due to its rapid spread and potential for causing debilitating epidemics. In Argentina, the virus has garnered attention since its introduction to the Americas in 2013, due to its growing incidence and impact in neighbouring countries. Here we present a comprehensive analysis of the spatiotemporal dynamics of CHIKV in Argentina, focusing on the evolutionary trajectory of its genetic variants. Through a combination of active surveillance, screening of historical and recent samples, and whole-genome sequencing, we traced the evolutionary history of CHIKV lineages circulating within the country. Our results reveal that two distinct genotypes circulated in Argentina: The Asian lineage during the 2016 epidemic and the ECSA lineage in 2023. This distribution reflects the dominance of particular variants across Latin America. Since 2023, the ECSA lineage has led to a surge in cases throughout the Americas, marking a significant shift. The replacement of lineages in the American region constitutes a major epidemiological event, potentially affecting the dynamics of virus transmission and the clinical outcomes in impacted populations. The spatiotemporal analysis highlights CHIKV's distribution across Argentina and underscores the significant role of human mobility, especially when considering recent epidemics in neighbouring countries such as Paraguay and Uruguay, which have facilitated the spread and introduction of the viral strain into different districts. By integrating epidemiological data with genomic insights, we elucidate the patterns of virus dissemination, highlighting key areas of transmission and potential factors contributing to its spread.

Epidemiology of Dengue in Argentina during the 2010/11 to 2019/20 Seasons: A Contribution to the Burden of Disease.

BACKGROUND: Dengue is an important public health problem in Argentina, as in many other countries. We reviewed and updated information on the dengue disease burden in Argentina over a 10-year period. METHODS: We conducted a retrospective descriptive study from 2010 to 2020 based on data from the National Health Surveillance System. The main outcomes included dengue cases, incidence rates, deaths, and serotype distribution by season, age group, and region. RESULTS: A total of 109,998 confirmed cases of dengue were reported. Seasonality stands out, prevailing during summer and autumn. Two main outbreaks (seasons 2015/16 and 2019/20), with increasing magnitude, were observed. The 2019/20 season showed the highest number of cases (58,731) and incidence rate (135/100,000). The Northeast region had the highest number of cases and incidence rate. In 2020, for the first time, autochthonous cases were registered in the Cuyo region. The only region with no autochthonous cases was the South. Adolescents and young adults showed the highest incidence rate. The case fatality rate for the period was 0.05%. Four serotypes circulated, but the predominant one was DEN-1 (78%). CONCLUSIONS: Dengue has been expanding temporally and spatially. Although the DEN-1 serotype widely predominated, the increasing circulation of other serotypes raises concerns regarding re-exposure and the severity of future cases. Understanding epidemiological trends is key to defining public prevention and control policies.

The Zika virus infection remodels the expression of the synaptotagmin-9 secretory protein.

The exact mechanisms involved in flaviviruses virions' release and the specific secretion of viral proteins, such as the Non Structural protein-1 (NS1), are still unclear. While these processes might involve vesicular transport to the cell membrane, NS1 from some flaviviruses was shown to participate in viral assembly and release. Here, we assessed the effect of the Zika virus (ZIKV) NS1 expression on the cellular proteome to identify trafficking-related targets that may be altered in the presence of the viral protein. We detected an increase in the synaptotagmin-9 (SYT9) secretory protein, which participates in the intracellular transport of protein-laden vesicles. We confirmed the effect of NS1 on SYT9 levels by transfection models while also detecting a significant subcellular redistribution of SYT9. We found that ZIKV prM-Env proteins, required for the viral particle release, also increased SYT9 levels and changed its localization. Finally, we demonstrated that ZIKV cellular infection raises SYT9 levels and promotes changes in its subcellular localization, together with a co-distribution with both Env and NS1. Altogether, the data suggest SYT9's implication in the vesicular transport of viral proteins or virions during ZIKV infection, showing for the first time the association of synaptotagmins with the flavivirus' life cycle.

Dengue más allá del trópico: estudio de series temporales 2015-2016 versus 2019-2020 en un hospital pediátrico de la Ciudad de Buenos Aires / Dengue beyond the tropics: a time-series study comprising 2015-2016 versus 2019-2020 at a children's hospital in the City of Buenos Aires

Introducción. El dengue es un problema de salud pública a nivel mundial. Confinado en sus orígenes a las zonas tropicales y subtropicales, en la actualidad se presenta en otras regiones como Argentina. Desde el año 2008 se presenta con brotes epidémicos en la Ciudad Autónoma de Buenos Aires, con escasos reportes en niños. Objetivo. Analizar y comparar las características clínicas, epidemiológicas, de laboratorio y evolutivas de los dos últimos brotes de dengue fuera del área endémica. Población y métodos. Estudio de series temporales. Se incluyeron pacientes menores de 18 años con dengue probable o confirmado, evaluados en un hospital pediátrico de la Ciudad de Buenos Aires durante los períodos 2015-2016 y 2019-2020. Resultados. Se incluyeron 239 pacientes, 29 (12 %) con antecedente de viaje. La mediana de edad fue de 132 meses (rango intercuartílico: 102-156). Todos tuvieron fiebre. Otros síntomas fueron: cefalea en 170 (71 %), mialgias en 129 (54 %) y exantema en 122 (51 %). Cuarenta pacientes (17 %) tenían comorbilidades. Presentaron signos de alarma 79 pacientes (33 %) y 14 (6 %) tenían dengue grave. Requirieron internación 115 pacientes (45 %) y ninguno falleció. El serotipo DENV-1 fue el más frecuente. El antecedente de viaje y la necesidad de internación predominaron en el primer período; el dengue grave y la infección previa, en el segundo. Conclusiones. Ningún paciente falleció de dengue en los períodos estudiados. Se observaron diferencias estadísticamente significativas en la frecuencia de internación; el antecedente de viaje fue más frecuente en el período 2015-2016 y el dengue grave, en el 2019-2020.

Introduction. Dengue is a public health problem worldwide. It was originally confined to tropical and subtropical areas, but it is now present in other regions, such as Argentina. Epidemic outbreaks have been observed in the City of Buenos Aires since 2008, with few reports in children. Objective. To analyze and compare the clinical, epidemiological, laboratory, and evolutionary characteristics of the latest 2 dengue outbreaks outside the endemic area. Population and methods. Time-series study. Patients under 18 years of age with probable or confirmed dengue and evaluated in a children's hospital of the City of Buenos Aires during the periods 2015-2016 and 2019-2020 were included. Results. A total of 239 patients were included; 29 (12%) had a history of travel. Their median age was 132 months (interquartile range: 102156). All had a fever. Other symptoms included headache in 170 (71%), myalgia in 129 (54%), and rash in 122 (51%). Forty patients (17%) had comorbidities. Warning signs were observed in 79 patients (33%); 14 (6%) developed severe dengue; 115 (45%) were hospitalized; none died. DENV-1 was the most common serotype. A history of travel and hospitalization prevailed in the first period; severe dengue and prior infection, in the second period. Conclusions. No patient died due to dengue in either study period. Statistically significant differences were observed in the frequency of hospitalization; a history of travel was more common in the 2015-2016 period and severe dengue, in the 2019-2020 period.

Dengue beyond the tropics: a time-series study comprising 2015-2016 versus 2019-2020 at a children's hospital in the City of Buenos Aires. / Dengue más allá del trópico: estudio de series temporales 2015-2016 versus 2019-2020 en un hospital pediátrico de la Ciudad de Buenos Aires.

INTRODUCTION: Dengue is a public health problem worldwide. It was originally confined to tropical and subtropical areas, but it is now present in other regions, such as Argentina. Epidemic outbreaks have been observed in the City of Buenos Aires since 2008, with few reports in children. OBJECTIVE: To analyze and compare the clinical, epidemiological, laboratory, and evolutionary characteristics of the latest 2 dengue outbreaks outside the endemic area. POPULATION AND METHODS: Time-series study. Patients under 18 years of age with probable or confirmed dengue and evaluated in a children's hospital of the City of Buenos Aires during the periods 2015-2016 and 2019-2020 were included. RESULTS: A total of 239 patients were included; 29 (12%) had a history of travel. Their median age was 132 months (interquartile range: 102- 156). All had a fever. Other symptoms included headache in 170 (71%), myalgia in 129 (54%), and rash in 122 (51%). Forty patients (17%) had comorbidities. Warning signs were observed in 79 patients (33%); 14 (6%) developed severe dengue; 115 (45%) were hospitalized; none died. DENV-1 was the most common serotype. A history of travel and hospitalization prevailed in the first period; severe dengue and prior infection, in the second period. CONCLUSIONS: No patient died due to dengue in either study period. Statistically significant differences were observed in the frequency of hospitalization; a history of travel was more common in the 2015-2016 period and severe dengue, in the 2019-2020 period.

Introducción. El dengue es un problema de salud pública a nivel mundial. Confinado en sus orígenes a las zonas tropicales y subtropicales, en la actualidad se presenta en otras regiones como Argentina. Desde el año 2008 se presenta con brotes epidémicos en la Ciudad Autónoma de Buenos Aires, con escasos reportes en niños. OBJETIVO: Analizar y comparar las características clínicas, epidemiológicas, de laboratorio y evolutivas de los dos últimos brotes de dengue fuera del área endémica. Población y métodos. Estudio de series temporales. Se incluyeron pacientes menores de 18 años con dengue probable o confirmado, evaluados en un hospital pediátrico de la Ciudad de Buenos Aires durante los períodos 2015-2016 y 2019-2020. RESULTADOS: Se incluyeron 239 pacientes, 29 (12 %) con antecedente de viaje. La mediana de edad fue de 132 meses (rango intercuartílico: 102-156). Todos tuvieron fiebre. Otros síntomas fueron: cefalea en 170 (71 %), mialgias en 129 (54 %) y exantema en 122 (51 %). Cuarenta pacientes (17 %) tenían comorbilidades. Presentaron signos de alarma 79 pacientes (33 %) y 14 (6 %) tenían dengue grave. Requirieron internación 115 pacientes (45 %) y ninguno falleció. El serotipo DENV-1 fue el más frecuente. El antecedente de viaje y la necesidad de internación predominaron en el primer período; el dengue grave y la infección previa, en el segundo. CONCLUSIONES: Ningún paciente falleció de dengue en los períodos estudiados. Se observaron diferencias estadísticamente significativas en la frecuencia de internación; el antecedente de viaje fue más frecuente en el período 2015-2016 y el dengue grave, en el 2019-2020.

Application of quantitative immunofluorescence assays to analyze the expression of cell contact proteins during Zika virus infections.

Zika Virus (ZIKV) is an RNA virus that belongs to the Flavivirus (FV) genus. In the last years, several unique characteristics of ZIKV among FV have been revealed, as the multiple routes of transmission and its ability to reach different human tissues, including the central nervous system. Thus, one of the most intriguing features of ZIKV biology is its ability to cross diverse complex biological barriers. The main aim of this study is to contribute to the understanding of the still unclear mechanisms behind this viral activity. We investigated an African strain and two South American ZIKV isolates belonging to the Asian lineage, in order to characterize possible differences regarding their ability to disturb intercellular junctions. The Asian isolates correspond to an imported (Venezuelan) and an autochthonous (Argentinian) ZIKV strain for which there is still no data available. We focused on occludin and DLG1 expression as markers of tight and adherent junctions, respectively. For this, we applied a quantitative immunofluorescence assay that can ascertain alterations in the cell junction proteins expression in the infected cells. Our findings indicated that the different ZIKV strains were able to reduce the levels of both polarity proteins without altering their overall cell distribution. Moreover, the grade of this effect was strain-dependent, being the DLG1 reduction higher for the African and Asian Venezuelan isolates and, on the contrary, occludin down-regulation was more noticeable for the Argentinian strain. Interestingly, among both junction proteins the viral infection caused a relative larger reduction in DLG1 expression for all viruses, suggesting DLG1 may be of particular relevance for ZIKV infections. Taken together, this study contributes to the knowledge of the biological mechanisms involved in ZIKV cytopathogenesis, with a special focus on regional isolates.

[Zika virus embryopathy in Argentina: clinical characteristics in newborns]. / Embriopatía por virus Zika en Argentina: características clínicas y diagnóstico en recién nacidos.

Introduction: Microcephaly and brain abnormalities may be due to multiple etiologies, one of them is the congenital infection by Zika virus (ZIKV). From 2016 to the present, there has been a series of ZIKV outbreaks in Argentina. Methods: National Network of Congenital Anomalies (RENAC) and the National Institute of Viral Diseases (INEVH), under the National Administration of Laboratories and Health Institutes "Carlos Malbrán" (ANLIS), carry out the intensified surveillance of newborns with microcephaly and brain abnormalities. This article presents the clinical characteristics and laboratory testof patients detected with congenital infection by ZIKV between April 2016 to March 2018, Results: 10 cases with embryopathy were detected, six autochthonous and four imported; in two cases, the mothers were asymptomatic during pregnancy; all the cases presented microcephaly and cranial facial disproportion, ventriculomegaly in seven cases and in six cerebral calcifications. The diagnosis of congenital infection by Zika in the newborn was made by antigen-specific Immunoglobulin M (MAC-ELISA) and plaque-reduction neutralization test (PRNT90 ). PCR was negative in all cases. Conclusion: the patients presented clinical features that were consistent with those reported in other countries. The need for serological studies that allow confirmation is emphasized, ruling out cross-reactivity with other Flaviviruses.

Introducción: La microcefalia y las anomalías cerebrales congénitas pueden deberse a múltiples etiologías, siendo uno de ellas la infección congénita por el virus Zika (ZIKV). Desde 2016 hasta hoy se han sucedido una serie de brotes del ZIKV en Argentina. Métodos: La Red Nacional de Anomalías Congénitas (RENAC) y el Instituto Nacional de Enfermedades Virales (INEVH), dependientes de la Administración Nacional de Laboratorios e Institutos de Salud "Carlos Malbrán" (ANLIS), realizan la vigilancia intensificada de recién nacidos con microcefalia y anomalías cerebrales. Este trabajo presenta las características clínicas y estudios de laboratorio de los pacientes con infección congénita por ZIKV detectados entre abril de 2016 a marzo 2018. Resultados: se detectaron 10 casos con embriopatía, seis fueron autóctonos y cuatro importados; en dos casos las madres fueron asintomática durante el embarazo; todos los casos presentaron microcefalia y desproporción cráneo facial, ventriculomegalia en siete casos y en seis calcificaciones cerebrales. El diagnóstico de infección congénita por Zika en el recién nacido se realizó por estudios serológicos inmunoglobulina M antígeno específica (MAC-ELISA) y prueba de neutralización por reducción de placas (PRNT90). La PCR fue negativa en todos los casos. Conclusión: Los pacientes presentaron características clínicas coincidentes con las reportadas en otros países Se enfatiza la necesidad de estudios serológicos que permitan la confirmación, descartando la reactividad cruzada con otros Flavivirus.

Simple production of hydrophobin-fused domain III of dengue envelope protein and induction of neutralizing antibodies against the homotypic serotype of dengue virus.

Hydrophobin-fused domain III of dengue envelope proteins serotypes 1 and 2 were expressed in Rachiplusia nu larvae and purified by aqueous two-phase system. This biotechnological approach of hydrophobin-fused proteins, which allowed obtaining 97.7 µg/larva of fusion protein DomIII serotype 1 and 61.4 µg/larva of fusion protein DomIII serotype 2, represents an integrated strategy for simple production of recombinant antigens. Purified fusion proteins induced serotype-specific neutralizing antibodies without cross-reaction against other serotypes and arboviruses after mouse immunization. hydrophobin-fused domain III of dengue envelope protein could be a promising strategy for easy and low-cost production of components of a tetravalent sub-unit vaccine against dengue.

Specific diagnostic method for St. Louis encephalitis virus using a non-structural protein as the antigen.

St. Louis encephalitis virus (SLEV) is a mosquito-borne re-emerging flavivirus in Argentina. It is currently necessary to develop specific serological tests that can efficiently discriminate the flaviviruses that circulate in our country. The immunoassays to diagnose SLEV lack specificity because they are based on the detection of structural viral proteins and the human immunoglobulins produced during infection against these proteins cross-react with other flaviviruses. Here, we describe an enzyme-immunoassay designed to detect human IgG antibodies specific to the viral non-structural protein NS5. The results indicate that NS5 is a promising antigen useful to discriminate SLEV from other circulating flaviviruses.

Elaboración de criterios epidemiológicos para estratificar por departamento poblacional de dengue grave / Development of Epidemiological Criteria to stratify by Department the Population Risk of Severe Dengue

: INTRODUCCIÓN: En Argentina desde 1998 ocurrieron brotes de dengue todos los años excepto 2001 y 2005 en diferentes áreas, en 15 jurisdicciones, con identificación de los 4 serotipos. El objetivo de este estudio fue identificar poblaciones con mayor riesgo de desarrollar formas graves de la enfermedad como insumo para la posible introducción de una estrategia de prevención. METODOS: Se realizó un estudio retrospectivo descriptivo de los casos de dengue confirmados autóctonos a partir de publicaciones oficiales, notificaciones al SNVS e información aportada por las áreas de epidemiología provinciales. Se elaboró una estratificación del riesgo de dengue grave por departamento para el período 1998-2018. RESULTADOS: Se elaboraron 5 criterios de estratificación de riesgo: registro de casos autóctonos en al menos 2 de los 5 cinco últimos años, registro de 2 o más serotipos causantes del 10% o más de los casos cada uno, incidencia acumulada mayor a 500 casos por 100 mil habitantes, incidencia acumulada mayor a 5 casos por mil menores de 15 años y registro de casos graves o fallecidos. Se obtuvieron 60 departamentos con 1 criterio, 19 con 2, 8 con 3, 4 con 4, 1 con 5 y 129 no cumplieron criterios. DISCUSION: Solo 13 departamentos sumaron 3 criterios o más, resultado del predominio de DENV-1, la baja incidencia en menores de 15 años y el bajo número de casos graves y fatales. La estratificación del riesgo poblacional con criterios de registro sistemático se orienta a obtener una herramienta de evaluación de los escenarios de dengue que puedan presentarse en el futuro.

Vector competence of Aedes aegypti for different strains of Zika virus in Argentina.

The importance of Zika virus (ZIKV) has increased noticeably since the outbreak in the Americas in 2015, when the illness was associated with congenital disorders. Although there is evidence of sexual transmission of the virus, the mosquito Aedes aegypti is believed to be the main vector for transmission to humans. This species of mosquito has not only been found naturally infected with ZIKV, but also has been the subject of study in many vector competence assays that employ different strains of ZIKV around the world. In Argentina, the first case was reported in February 2016 and a total of 278 autochthonous cases have since been confirmed, however, ZIKV virus has not been isolated from any mosquito species yet in Argentina. In order to elucidate if Argentinian Ae. aegypti populations could be a possible vector of ZIKV, we conducted vector competence studies that involved a local strain of ZIKV from Chaco province, and a Venezuelan strain obtained from an imported case. For this purpose, Ae. aegypti adults from the temperate area of Argentina (Buenos Aires province) were fed with infected blood. Body, legs and saliva were harvested and tested by plaque titration on plates of Vero cells for ZIKV at 7, 11 and 14 days post infection (DPI) in order to calculate infection, transmission, and dissemination rates, respectively. Both strains were able to infect mosquitoes at all DPIs, whereas dissemination and transmission were observed at all DPIs for the Argentinian strain but only at 14 DPI for the Venezuelan strain. This study proves the ability of Ae. aegypti mosquitoes from Argentina to become infected with two different strains of ZIKV, both belonging to the Asian lineage, and that the virus can disseminate to the legs and salivary glands.

Surveillance of microcephaly and selected brain anomalies in Argentina: Relationship with Zika virus and other congenital infections.

BACKGROUND: Zika virus (ZIKV) vertical transmission may lead to microcephaly and other congenital anomalies. In March and April 2016, the first outbreak of ZIKV occurred in Argentina. The objective was to describe the surveillance of newborns with microcephaly and other selected brain anomalies in Argentina, and evaluation different etiologies. METHODS: Participants were enrolled between April 2016 and March 2017. CASES: newborns from the National Network of Congenital Abnormalities of Argentina (RENAC) with head circumference lower than the 3rd percentile according to gestational age and sex, or selected brain anomalies. Blood and urine samples from cases and their mothers were tested for ZIKV by real-time polymerase chain reaction (RT-PCR), antigen-specific Immunoglobulin M (MAC-ELISA) and plaque-reduction neutralization test (PRNT90 ). Toxoplasmosis, rubella, herpes simplex, syphilis, and cytomegalovirus (CMV) infection were also tested. RESULTS: A total of 104 cases were reported, with a prevalence of 6.9 per 10,000 [95% confidence interval (CI): 5.7-8.4], a significant increase when compared with the data prior to 2016, Prevalence Rate Ratio 1.7 (95% CI 1.2-2.3). In five cases positive serology for ZIKV (IgM and IgG by PRNT) was detected. The five cases presented microcephaly with craniofacial disproportion. We detected four cases of CMV infection, three cases of congenital toxoplasmosis, two cases of herpes simplex infection, and one case of congenital syphilis. CONCLUSION: The prevalence of microcephaly was significantly higher when compared with the previous period. The system had the capacity to detect five cases with congenital ZIKV syndrome in a country with limited viral circulation.

Detection of the mosquito-borne flaviviruses, West Nile, Dengue, Saint Louis Encephalitis, Ilheus, Bussuquara, and Yellow Fever in free-ranging black howlers (Alouatta caraya) of Northeastern Argentina.

Several medically important mosquito-borne flaviviruses have been detected in Argentina in recent years: Dengue (DENV), St. Louis encephalitis (SLEV), West Nile (WNV) and Yellow Fever (YFV) viruses. Evidence of Bussuquara virus (BSQV) and Ilheus virus (ILHV) activity were found, but they have not been associated with human disease. Non-human primates can act as important hosts in the natural cycle of flaviviruses and serological studies can lead to improved understanding of virus circulation dynamics and host susceptibility. From July-August 2010, we conducted serological and molecular surveys in free-ranging black howlers (Alouatta caraya) captured in northeastern Argentina. We used 90% plaque-reduction neutralization tests (PRNT90) to analyze 108 serum samples for antibodies to WNV, SLEV, YFV, DENV (serotypes 1and 3), ILHV, and BSQV. Virus genome detection was performed using generic reverse transcription (RT)-nested PCR to identify flaviviruses in 51 antibody-negative animals. Seventy animals had antibodies for one or more flaviviruses for a total antibody prevalence of 64.8% (70/108). Monotypic (13/70, 19%) and heterotypic (27/70, 39%) patterns were differentiated. Specific neutralizing antibodies against WNV, SLEV, DENV-1, DENV-3, ILHV, and BSQV were found. Unexpectedly, the highest flavivirus antibody prevalence detected was to WNV with 9 (8.33%) monotypic responses. All samples tested by (RT)-nested PCR were negative for viral genome. This is the first detection of WNV-specific antibodies in black howlers from Argentina and the first report in free-ranging non-human primates from Latin-American countries. Given that no animals had specific neutralizing antibodies to YFV, our results suggest that the study population remains susceptible to YFV. Monitoring of these agents should be strengthened to detect the establishment of sylvatic cycles of flaviviruses in America and evaluate risks to wildlife and human health.

Tenosinovitis por virus Chikungunya / Tenosynovitis due to Chikungunya virus

Se presenta a la consulta un hombre proveniente de la República Dominicana con una tenosinovitis del extensor del dedo medio derecho; en la convalecencia inmediata, segunda curva febril luego de 48 horas de permanecer asintomático de una enfermedad febril aguda, y marcada astenia, exantema pruriginoso, poliartralgias con impotencia funcional y rigidez articular generalizada. Los exámenes bioquímicos no aportaron datos de interés para el diagnóstico. La serología para virus dengue fue negativa. La detección de IgM y de anticuerpos neutralizantes para virus Chikungunya (CHIKV) fueron positivos.

We report the case of a man from Dominican Republic who consulted for a tenosynovitis of the right middle finger extensor; in the immediate convalescence second febrile curve, after 48 hours of no symptoms of an acute febrile illness, with marked fatigue, itchy rash, polyarthralgia, functional impairment and general stiffness. Biochemical tests did not provide useful data for diagnosis. Dengue virus serology was negative. Detection of IgM and neutralizing antibodies (PRNT) for Chikundunya virus (CHIKV) were positive.

[Tenosynovitis due to Chikungunya virus]. / Tenosinovitis por virus Chikungunya.

We report the case of a man from Dominican Republic who consulted for a tenosynovitis of the right middle finger extensor; in the immediate convalescence second febrile curve, after 48 hours of no symptoms of an acute febrile illness, with marked fatigue, itchy rash, polyarthralgia, functional impairment and general stiffness. Biochemical tests did not provide useful data for diagnosis. Dengue virus serology was negative. Detection of IgM and neutralizing antibodies (PRNT) for Chikundunya virus (CHIKV) were positive.

[Outbreak of St. Louis encephalitis in the Metropolitan Buenos Aires Area]. / Brote de encefalitis de San Luis en el área metropolitana Buenos Aires.

We describe the epidemiological and clinical findings of 13 patients with diagnosis of infection by St. Louis encephalitis virus, transmitted between January and March 2010 in Buenos Aires Metropolitan Area (AMBA). Thirteen patients, average age 38 years, had an acute onset with hyperthermia and headache. Between days two and ten of the onset of symptoms, 7/13 patients had signs and symptoms of neurological involvement. This was characterized by meningitis without encephalic sings in 1/7 and in 6/7 the most frequent findings were: stiff neck, disorientation, photophobia, confusion and language impairment. Two MR and one EEG revealed signs of involvement of temporal lobes. The cerebrospinal fluid showed pleocytosis with predominance of mononuclear cells, normal glucose and moderately elevated protein. There were no fatalities cases. In 6/13 patients the initial clinical suspicion was dengue. As epidemic virus circulation had not been previously reported in the AMBA it can be considered an outbreak of St. Louis encephalitis for the spatial and temporal clustering of cases.

Brote de encefalitis de San Luis en el Área Metropolitana Buenos Aires / Outbreack of St. Luis encephalitis in the Metropolitan Buenos Aires Area

Se describen los hallazgos epidemiológicos y clínicos de 13 enfermos con diagnóstico de infección por virus de la encefalitis de San Luis, con transmisión entre enero y marzo de 2010, en el Area Metropolitana Buenos Aires (AMBA). Los 13 enfermos, promedio de edad 38 años, tuvieron un comienzo agudo caracterizado por hipertermia y cefalea. Entre los días dos y diez de iniciados los síntomas, 7/13 enfermos tuvieron signos y síntomas de compromiso neurológico caracterizado por meningitis sin signos encefálicos en 1/7. En 6/7 los hallazgos más frecuentes fueron: rigidez de nuca, desorientación temporoespacial, fotofobia, confusión y alteración del lenguaje. Dos resonancias magnéticas y un electroencefalograma presentaron signos de afectación de lóbulos temporales. El líquido cefalorraquídeo se caracterizó por pleocitosis con predominio de células mononucleadas, glucorraquia normal y discreto aumento de proteínas. No hubo casos fatales. En 6/13 pacientes la sospecha clínica inicial fue dengue. Por la agrupación espacial y temporal de los casos puede considerarse un brote epidémico, el primero conocido en el AMBA, ya que no se había notificado previamente la circulación epidémica del virus.

We describe the epidemiological and clinical findings of 13 patients with diagnosis of infection by St. Louis encephalitis virus, transmitted between January and March 2010 in Buenos Aires Metropolitan Area (AMBA). Thirteen patients, average age 38 years, had an acute onset with hyperthermia and headache. Between days two and ten of the onset of symptoms, 7/13 patients had signs and symptoms of neurological involvement. This was characterized by meningitis without encephalic sings in 1/7 and in 6/7 the most frequent findings were: stiff neck, disorientation, photophobia, confusion and language impairment. Two MR and one EEG revealed signs of involvement of temporal lobes. The cerebrospinal fluid showed pleocytosis with predominance of mononuclear cells, normal glucose and moderately elevated protein. There were no fatalities cases. In 6/13 patients the initial clinical suspicion was dengue. As epidemic virus circulation had not been previously reported in the AMBA it can be considered an outbreak of St. Luis encephalitis for the spatial and temporal clustering of cases.