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We evaluated humoral immune-response elicited by Sputnik-V by measuring anti-Spike (S) IgG antibodies (Abs) and neutralizing antibodies (NAb) prior to, 14 and 42 days after-vaccination. The safety and disease rates among vaccinated individuals were also evaluated. Since SARS-CoV-2 lineage P.1 is rapidly spreading in Argentina, virus-neutralizing activity of Sputnik-V-elicited and infection-elicited NAb faced to P.1 were also assessed. A total of 285 participants were recruited; all reported good tolerance, without any severe adverse event. Nine COVID-19 cases were confirmed in fully vaccinated individuals and viable P.1 variant was successfully isolated from one of them. At day 42, 99.65% of the individuals had anti-S IgG; however, 23.15% had not detectable NAbs. Significantly higher neutralization potency against WT compared to P.1 (p

Heterologous Covid-19 vaccination strategies arose due to interruption of vaccination programs plus delay and shortage of vaccine supplies. We analysed neutralizing response against ancestral SARS-CoV-2 B.1 and P.1, C.37 and B.1.67.2 variants elicited by 16 homologous and heterologous protocols combining Gam-COVID-Vac, ChAdOx1-S, Ad5-nCorV, BBIBP-CorV and mRNA-1273 vaccines. Homologous mRNA-1273 and heterologous schemes of a non-replicative viral vector/inactivated virus-based vaccine combined with mRNA-1273 induced significantly broader and greater neutralizing antibody-response. Moreover, serum from participants vaccinated with combinations of ChAdOx1-S/Ad5-nCorV and BBIBP-CorV/non-replicative viral vector-based vaccines showed higher or equivalent neutralizing response compared to homologous protocols, pointing them as good alternative platforms. BBIBP-CorV used as second dose exhibited significantly lower neutralizing response compared to other protocols, demonstrating that it should not be recommended as second dose. The information provided herein is valuable to redesign vaccination strategies, especially for low-income countries that still struggle with low percentages of immunized populations and vaccine supply shortage., Fil: Blanco, Sebastián. Universidad Nacional de Córdoba. Facultad de Ciencias Médicas. Instituto de Virología “Dr. J. M. Vanella”; Argentina, Fil: Spinsanti, Lorena. Universidad Nacional de Córdoba. Facultad de Ciencias Médicas. Instituto de Virología “Dr. J. M. Vanella”; Argentina, Fil: Aguilar, Juan Javier. Universidad Nacional de Córdoba. Facultad de Ciencias Médicas. Instituto de Virología “Dr. J. M. Vanella”; Argentina, Fil: Diaz, Adrián. Universidad Nacional de Córdoba. Facultad de Ciencias Médicas. Instituto de Virología “Dr. J. M. Vanella”; Argentina, Fil: Diaz, Adrián. CONICET; Argentina, Fil: Rivarola, María Elisa. Universidad Nacional de Córdoba. Facultad de Ciencias Médicas. Instituto de Virología “Dr. J. M. Vanella”; Argentina, Fil: Beranek, Mauricio. Universidad Nacional de Córdoba. Facultad de Ciencias Médicas. Instituto de Virología “Dr. J. M. Vanella”; Argentina, Fil: Beranek, Mauricio. CONICET; Argentina, Fil: Fernández, Elmer. Universidad Católica de Córdoba. Centro de Investigación y Desarrollo en Inmunología y Enfermedades Infecciosas; Argentina, Fil: Fernández, Elmer. CONICET; Argentina, Fil: Mangeaud, Arnaldo. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales; Argentina, Fil: Konigheim, Brenda Salomé. Universidad Nacional de Córdoba. Facultad de Ciencias Médicas. Instituto de Virología “Dr. J. M. Vanella”; Argentina, Fil: Konigheim, Brenda Salomé. CONICET; Argentina, Fil: Gallego, Sandra Verónica. Universidad Nacional de Córdoba. Facultad de Ciencias Médicas. Instituto de Virología “Dr. J. M. Vanella”; Argentina, Fil: Gallego, Sandra Verónica. CONICET; Argentina

Background To analyze the infectious extent of severe acute respiratory syndrome coronavirus 2 (SARS-COV-2) in different settings where prevention strategies are critical to limit infection spread, we evaluated SARS-COV-2 viability to guide public health policies regarding isolation criteria and infection control. Methods We attempted viral isolation in 82 nasopharyngeal swabs from 72 patients with confirmed SARS-COV-2 infection. Study population was divided into four groups: (i) Patients during the first week of symptoms; (ii) Patients with prolonged positive PCR; (iii) Healthcare workers from a hospital participating of an outbreak investigation, with SARS-COV-2 infection confirmed by reverse transcriptase polymerase chain reaction (RT-PCR) and (iv) Recipients of convalescent immune plasma (CIP). Vero Cl76 cell-line (ATCC CRL-587) was used in assays for virus isolation. Plasma samples of CIP recipients were also tested with plaque-reduction neutralization test. Results We obtained infectious SARS-COV-2 isolates from 15/84 nasopharyngeal swabs. The virus could not be isolated from upper respiratory tract samples collected 10-day after onset of symptoms (AOS) in patients with mild moderate disease. Conclusion The knowledge of the extent of SARS-CoV-2 infectivity AOS is relevant for effective prevention measures. This allows to discuss criteria for end isolation despite persistence of positive PCR and improve timing for hospital discharge with consequent availability of critical beds. Fil: Blanco, Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentina. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología Dr. J. M. Vanella; Argentina Fil: Aguilar, Juan Javier. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología Dr. J. M. Vanella; Argentina Fil: Konigheim, Brenda Salome. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología Dr. J. M. Vanella; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentina Fil: Diaz, Luis Adrian. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología Dr. J. M. Vanella; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentina Fil: Spinsanti, Lorena Ivana. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología Dr. J. M. Vanella; Argentina Fil: Beranek, Mauricio Daniel. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología Dr. J. M. Vanella; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentina Fil: Collino, César. Hospital Público Descentralizado Dr. Guillermo Rawson.; Argentina Fil: Diaz, Miguel. Ministerio de Salud de la Provincia de Córdoba; Argentina Fil: Barbás, María Gabriela. Hospital Público Descentralizado Dr. Guillermo Rawson.; Argentina Fil: Gallego, Sandra Veronica. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología Dr. J. M. Vanella; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba; Argentina

Flaviviruses are responsible for several emerging mosquito-borne diseases in Argentina and in the Americas. Some of these diseases are zoonosis and were detected in recent years: West Nile virus (WNV) and Saint Louis encephalitis virus (SLEV) among them. WNV originated in Africa was detected for the first time in America in 1999 and it was first isolated from diseased and dead horses in 2006 in Argentina. Neutralizing antibodies from wild birds, humans and horses have been also detected in later years. SLEV re-emerged as a human pathogen in Argentina with the first epidemic in 2005. During this outbreak, viral strains were isolated from Culex mosquitoes and several studies have detected neutralizing antibodies from birds, human and horses, in the last ten years.The aim of this work is to provide information on the activity of the Flavivirus SLEV and WNV, identifying the infection in horses in three localities of the province of Chaco. From May 2013 to May 2014, serological surveys from 68 asymptomatic horses were conducted. Antibodies against SLEV (25 %) and WNV (8.82%) were detected. This is the first report of WNV circulation in equines from Chaco province and circulation of both viruses during the study period was demonstrated. Fil: Oria, Griselda Inés. Universidad Nacional del Nordeste. Instituto de Medicina Regional; Argentina. Fil: Spinsanti, Lorena Ivana. Universidad Nacional de Córdoba. Facultad de Ciencias Médicas; Argentina. Fil: Pirota, Verónica Laura. Ministerio de la Producción. Dirección de Fauna; Argentina. Fil: Martínez, María Silvana. Universidad Nacional del Nordeste. Facultad de Ciencias Económicas; Argentina. Fil: Stechina, Ornela Sofía. Universidad Nacional del Nordeste. Instituto de Medicina Regional; Argentina. Fil: Stechina, Ornela Sofía. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Nordeste; Argentina. Fil: Etchepare, Eduardo Gabriel. Universidad Nacional del Nordeste. Facultad de Ciencias Exactas y Naturales y Agrimensura; Argentina. Fil: Contigiani, Marta Silvia. Universidad Nacional de Córdoba. Facultad de Ciencias Médicas; Argentina. Fil: Stein, Marina. Universidad Nacional del Nordeste. Instituto de Medicina Regional; Argentina. Fil: Stein, Marina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Nordeste; Argentina.

Saint Louis encephalitis virus (SLEV) reemerged in South America, and caused encephalitis outbreaks at the beginning of the 21st century. To enhance our knowledge about SLEV virulence, we performed comparative pathogenesis studies in Swiss albino mice inoculated with two different variants, the epidemic strain CbaAr-4005 and the non-epidemic strain CorAn-9275. Only the infection of mice with SLEV strain CbaAr-4005 resulted in high viremia, invasion of peripheral tissues including the lungs, kidney, and spleen, and viral neuroinvasion. This was associated with inflammatory pathology in the lungs, spleen, and brain as well as morbidity and mortality. In contrast, neither signs of desease nor viral replication were observed in mice infected with strain CorAn-9275. Interestingly, important loss of B cells and development of altered germinal centers (GC) were detected in the spleen of mice infected with strain CbaAr-4005, whereas mice infected with SLEV CorAn-9275 developed prominent GC with conserved follicular architecture, and neutralizing antibodies. Fil: Rivarola, María Elisa. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología ; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones Biológicas y Tecnológicas. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto de Investigaciones Biológicas y Tecnológicas; Argentina Fil: Albrieu Llinás, Guillermo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones Biológicas y Tecnológicas. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto de Investigaciones Biológicas y Tecnológicas; Argentina. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología ; Argentina Fil: Pisano, María Belén. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones Biológicas y Tecnológicas. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto de Investigaciones Biológicas y Tecnológicas; Argentina. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología ; Argentina Fil: Tauro, Laura Beatriz. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología ; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones Biológicas y Tecnológicas. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto de Investigaciones Biológicas y Tecnológicas; Argentina Fil: Gorosito Serran, Melisa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones Biológicas y Tecnológicas. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto de Investigaciones Biológicas y Tecnológicas; Argentina. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas; Argentina Fil: Beccaria, Cristian Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones Biológicas y Tecnológicas. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto de Investigaciones Biológicas y Tecnológicas; Argentina. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas; Argentina Fil: Diaz, Luis Adrian. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología ; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones Biológicas y Tecnológicas. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto de Investigaciones Biológicas y Tecnológicas; Argentina Fil: Vázquez, Ana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones Biológicas y Tecnológicas. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto de Investigaciones Biológicas y Tecnológicas; Argentina. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología ; Argentina Fil: Quaglia, Agustín Ignacio Eugenio. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología ; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones Biológicas y Tecnológicas. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto de Investigaciones Biológicas y Tecnológicas; Argentina Fil: López, Cristina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones Biológicas y Tecnológicas. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto de Investigaciones Biológicas y Tecnológicas; Argentina. Universidad Nacional de Córdoba. Facultad de Ciencias Médicas; Argentina Fil: Spinsanti, Lorena Ivana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones Biológicas y Tecnológicas. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto de Investigaciones Biológicas y Tecnológicas; Argentina. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología ; Argentina Fil: Gruppi, Adriana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones Biológicas y Tecnológicas. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto de Investigaciones Biológicas y Tecnológicas; Argentina. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas; Argentina Fil: Contigiani de Minio, Marta Silvia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones Biológicas y Tecnológicas. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto de Investigaciones Biológicas y Tecnológicas; Argentina. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología ; Argentina

St. Louis encephalitis virus (SLEV) and West Nile virus (WNV) present ecological and antigenic similarities and are responsible for serious human diseases. In addition, WNV is a significant pathogen in terms of equine health. The purpose of our study was to analyse the seroprevalence of SLEV and WNV in equine sera collected in Santa Fe Province, Argentina. The seroprevalence determined using the plaque reduction neutralisation test was 12.2% for SLEV, 16.2% for WNV and 48.6% for a combination of both viruses. These results provide evidence of the co-circulation of SLEV and WNV in equines in Santa Fe.

Nuestro objetivo fue conocer la presencia de anticuerpos neutralizantes contra el virus de la encefalitis de San Luis (St. Louis encephalitis virus [SLEV]) y el virus del Nilo Occidental (West Nile virus [WNV]) en sueros de aves silvestres y domésticas de la Ciudad Autónoma de Buenos Aires, Argentina. Desde octubre del 2012 hasta abril del 2013 se colectaron 180 muestras que fueron procesadas por la técnica de microneutralización. El 7,2 % de las aves muestreadas resultaron seropositivas para SLEV, mientras que no se detectaron aves seropositivas para WNV. Our goal was to determine the presence of neutralizing antibodies against St. Louis encephalitis virus (SLEV) and West Nile virus (WNV) in sera of wild and domestic birds from Buenos Aires City, Argentina. From October 2012 to April 2013, 180 samples were collected and processed by the microneutralization technique. A 7.2 % of the sampled birds were seropositive for SLEV, while no seropositive birds for WNV were detected. Fil: Beltrán, Fernando J.. Ciudad Autónoma de Buenos Aires. Ministerio de Salud; Argentina Fil: Díaz, Luis A.. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología “Dr. J. M. Vanella”; Argentina Fil: Konigheim, Brenda Salome. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología “Dr. J. M. Vanella”; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Molina, José. Ciudad Autónoma de Buenos Aires. Ministerio de Salud; Argentina Fil: Beaudoin, Juan B.. Ciudad Autónoma de Buenos Aires. Ministerio de Salud; Argentina Fil: Contigiani de Minio, Marta Silvia. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología “Dr. J. M. Vanella”; Argentina Fil: Spinsanti, Lorena Ivana. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología “Dr. J. M. Vanella”; Argentina

A serological screening was performed in 615 individuals aged 0-87 years, living in the city of Cordoba, Argentina to study the relationship between antibody prevalence for the SLE virus and age. A 13.98% prevalence of neutralizing antibodies was obtained and its relation to age was significantly high (p = 0.045). The highest seroprevalence was noted on individuals over 60 years old (>20%), whereas no subject under 10 was seropositive for this virus. Our results confirm that the agent is endemic in this area and neurological pathology studies should be performed on those individuals aged 60 since they represent the most susceptible group to SLE virus.

To the Editor: West Nile virus (WNV), genus Flavivirus, family Flaviviridae has been rapidly dispersing through the Americas since its introduction in 1999 in New York (1). By 2004, serologic studies detected WNV-specific antibodies in birds and horses from Canada to northern South America (2–4). The first report of WNV activity in the Southern Cone of South America surfaced in April 2006, when 3 horses died in Argentina (5). However, established transmission foci in Argentina are unknown. We report evidence for the introduction and establishment of WNV in Argentina as early as January 2005. Serum samples from free-ranging birds were collected from 5 locations in Argentina and screened for generic flavivirus antibodies by using a blocking ELISA with monoclonal antibody 6B6C-1 (6). Positive serum specimens were further characterized by plaque-reduction neutralization test (PRNT). We identified the etiologic agent responsible for the previous flavivirus infection by using the following criteria: 80% neutralization of reference virus (WNV NY99-4132 or an Argentinean strain of St. Louis encephalitis virus [SLEV CbaAr4005]) in serum diluted at least 1:40 and 4-fold greater titer compared with the other virus. Overall, 474 (25.6%) of 1,845 serum specimens from 117 bird species collected from January to June 2006 tested positive when using the blocking ELISA; 30% inhibition was the threshold for a positive test. SLEV infections were confirmed in 105 birds by PRNT; WNV infections were confirmed in 43 birds. Anti-WNV antibody titers ranged from 40 to 2,560 in birds collected as early as January 2005 in Cordoba City and as late as June 2006 in Mar Chiquita (Table). Recent WNV activity was indicated by seroconversion in 3 banded rufous hornero in Cordoba City between January and March 2005. Although 659 (1.5%) of serum samples were positive for SLEV, no WNV infection was detected in free-ranging birds collected in 2004. As early as January 2005, WNV was detected in a seroconversion so we suspect WNV was introduced before 2005 at the end of 2004 in all 5 sampling locations and in a variety of ecosystems: Cordoba, periurban (1.1%, 6/543); Mar Chiquita, thorn forest (5.1%, 16/313); Monte Alto, semidry chaco forest (9.8%, 8/82); Montecristo, cropland (9.5%, 2/21); and San Miguel de Tucuman, periurban yungas foothills (4.9%, 12/227). Table Prevalence of West Nile virus–neutralizing antibodies among birds grouped by taxonomic family, sampled in Chaco, Cordoba, and Tucuman Provinces, Argentina, 2004–2006* In 2006, WNV was isolated from equines in Buenos Aires province (5). WNV transmission to resident birds collected further north in Cordoba, Chaco, and Tucuman provinces was detected in 2005 and 2006. Our data suggest that WNV was introduced into Argentina before 2005 and maintained naturally in enzootic foci where numerous bird species from many families were exposed. Presumably, as in North America, locally abundant passerine birds such as turdids (thrushes) are amplifying hosts. If common species of the Furnariidae (a family absent from temperate North America) prove to be competent hosts, they could play an important role in WNV transmission in Argentina because of their frequent exposure to WNV. Twelve (12.5%) of 96 F. ruffus sampled in 2005 and 2006 tested positive. How WNV reached Argentina may never be known. Dispersal by migrating birds is a popular hypothesis, although relatively few North American breeding birds migrate to Argentina, and austral migrants number fewer than boreal migrants. Komar and Clark (2) suggested that bird species in the order Charadriiformes, such as shorebirds and terns, are candidates for carrying WNV from North America to South America due to long lasting high-level viremias, occasional persistent infectious viral loads in skin, and direct, long-distance flights. WNV spread southward from the United States to northern South America between 1999 and 2004 following a stepping stone pattern, consistent with spread by birds. Moreover, introduction of WNV into Argentina by migratory birds could explain the presence of the virus in many places in a brief period. However, for migratory birds (211 serum samples tested) in this study, serologic test results were negative. The high titers of WNV-reactive antibody are strongly indicative of WNV infections. Overall, 216 serum specimens reacted by PRNT test against SLEV, WNV or both at titers ≥20. Sixty-eight serum samples remain unidentified. The large number of unidentified flavivirus-positive samples detected by PRNT, ELISA, or both (148/474) could be due to 1) false positives; 2) cross-reactions between WNV- and SLEV-reactive antibodies that prevented definitive diagnosis by PRNT; 3) cross-reactive antibody and multiple, heterologous flavivirus infections; 4) previous infections by both WNV and SLEV; and/or 5) presence of other flaviviruses circulating in Argentina. SLEV is endemic throughout Argentina and, like WNV, belongs to the Japanese encephalitis virus serocomplex. Hemagglutination-inhibiting antibodies against several Brazilian flaviviruses (e.g., Bussuquara, Ilheus, Rocio viruses) have been reported in the neotropical region of extreme northern Argentina (7), but these viruses have not been isolated in Argentina. Our serologic data suggest that WNV has established itself in 4 ecologic regions in Argentina in a brief period. Additional studies are needed to define the reservoir hosts and vectors of WNV in Argentina, and most importantly, to define the public health risk this virus represents.

Twenty-six years after it was last detected, Saint Louis encephalitis virus (SLEV) genotype III reemerged in 2005 in Córdoba, 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.

St. Louis encephalitis virus (SLEV) and West Nile virus (WNV) belong to the Japanese encephalitis antigenic complex (Flavivirus genus, Flaviviridae family). They show antigenic close relationships and share many similarities in their ecology. Both are responsible for serious human diseases. The aim of this study was to investigate the presence of neutralizing antibodies to these viruses in horses from Uruguay. To do this, 425 horse sera were collected in 2007 and analyzed by plaque reduction neutralization tests. As a result, 205 sera (48.2%) were found positive for SLEV, with titers ranging between 10 and 80. Two sera remained inconclusive, since they showed low titers to WNV and SLEV (10 and 20), not allowing us to demonstrate activity of WNV in our territory. This is the first report of circulation of SLEV in horses in Uruguay. Fil: Burgueño, Analía. Universidad de la República. Facultad de Ciencias; Uruguay Fil: Spinsanti, Lorena Ivana. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Diaz, Luis Adrian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones Biológicas y Tecnológicas. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto de Investigaciones Biológicas y Tecnológicas; Argentina Fil: Rivarola, María Elisa. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Arbiza, Juan. Universidad de la República. Facultad de Ciencias; Uruguay Fil: Contigiani de Minio, Marta Silvia. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Delfraro, Adriana. Universidad de la República. Facultad de Ciencias; Uruguay

To the Editor: St. Louis encephalitis is a mosquito-borne viral disease that affects humans. The causative agent, SLEV (formal name: Saint Louis encephalitis virus), is a member of the Flaviviridae family. Severity of the clinical syndromes increases with age, and persons >60 years old have the highest frequency of encephalitis. The primary transmission cycle involves wild passeiform, columbiform birds, and Culex sp. mosquitoes (1). In Argentina, an urban cycle may involve Cx. quinquefasciatus, which is a source of a viral isolate, and abundant birds (house sparrows, doves, or chickens) (2). The distribution of SLEV in Argentina is wide; seroprevalence ranges from 3% to 50% of the country’s population (3). Spinsanti et al. reported results of a serologic screening in persons ages 0–87 years who live in the city of Cordoba; antibodies were most frequently found in persons >60 years of age (4). However, cases of St. Louis encephalitis reported in Argentina are very rare. Two cases with serologic diagnosis were reported in 1964 and 1968, respectively (2). In 1971, two more cases were diagnosed on the basis of viral isolation (5). Finally, the last case reported was a patient with meningoencephalitis diagnosed in the province of Buenos Aires by hemagglutination inhibition assay (6). Herein, we report a case of Saint Louis encephalitis that occurred in the province of Cordoba, Argentina. A 61-year-old man was admitted to the hospital in February 2002, complaining of headache, fever, and diplopia. He had been well until 3 months before admission, when ophthalmic herpes zoster was diagnosed. He underwent therapy with oral acyclovir and had a good clinical outcome. Ten days before admission, he developed unstable gait with misbalance and hand tremors, mainly at his left side. On admission, he had occipital headache, diplopia, and nausea and vomiting associated with high fever and chills. Somnolence appeared a few hours before the consultation. The patient was a right-handed businessman, a native of Cordoba. He was married and had no risk factors for sexually transmitted diseases. He had not traveled inside or outside the country during the last year. He lived near a river with a high-density population of mosquitoes. Vital signs on admission showed axillary temperature of 39°C, pulse of 90 beats per minute, respiratory frequency of 20 per minute, and blood pressure of 110/70 mmHg. Physical examination demonstrated a somnolent patient who was easily aroused and oriented. His speech was slurred. Results of a fundoscopic examination appeared normal. Results of a cranial-nerve examination showed horizontal left diplopia with left sixth nerve paresia. A resting, postural, and intentional hand tremor was evident. Motor strength was 5/5 throughout with normal bulk and tone, tendon reflexes, and coordination. Examination of sensitivity showed no abnormalities. A slight neck rigidity was detected. Routine laboratory analysis was unremarkable, and results of serologic tests for coxsackie virus, echovirus, and HIV were negative. HIV-1 RNA by polymerase chain reaction (PCR) and p24 antigen were also negative. Cerebrospinal fluid study revealed a leukocyte count of 18/mm3 (80% lymphocytes), a glucose level of 48 mg/dL, and a protein level of 87 mg/dL. Cryptococcal antigen, antibodies for syphilis, Human herpesvirus 1 and 2, and PCR for varicella-zoster virus 1 and Human herpesvirus were also negative. Results of an electroencephalogram and a chest radiograph were normal. Therapy with intravenous acyclovir was initiated. A magnetic resonance imaging (MRI) scan of the brain showed a striking signal change on T2 in the substantia nigra of the midbrain, mainly at the right side. The patient continued febrile, diplopia disappeared, and meningeal signs progressed with frank cervical stiffness, positive Kerning sign, and photophobia. Diffuse tremulousness and axial rigidity appeared. Upper extremities showed rigidity with cogwheel phenomenon. Conversely, lower extremities showed spasticity with bilateral Babinski sign. Tendon reflexes became enhanced. His gait showed retropulsion with wide base sustentation. Dysdiadochokinesia appeared. On the third day, a new lumbar puncture showed worse results: a leukocyte count of 210/mm3 (82% lymphocytes), a glucose level of 51 mg/dL, and a protein level of 106 mg/dL. Another electroencephalographic examination showed unspecific centroparietal disorganization with right side predominance. Intravenous acyclovir was stopped. On the 5th day, the patient began to recover; he was discharged on the 10th day. After 3 months of follow-up, only left arm rigidity and a left hand tremor persisted. Acute- and convalescent-phase serum samples (taken 10 and 16 days after onset of illness, respectively) were sent to the Arbovirus and Arenavirus Disease Laboratory, Instituto de Virologia, Cordoba. SLEV immunoglobulin (Ig) M antibodies were positive by indirect immunofluorescence assay (IFA). Seroconversion for IgG antibodies was demonstrated by IFA (7) and hemagglutination inhibition assay, with titers of 640 and 80 in the first sample and 2,560 and 320 in the second sample. These results were confirmed by neutralization test using the reduction of plates technique in Vero cells culture, as described (8). Eastern equine encephalomyelitis virus and Western equine encephalomyelitis viruses with known circulation in Argentina were included in the assay with negative results (3). An increase in antibodies titers between acute- (320) and convalescent-phase (1,280) samples was found only for SLEV. Among other flaviviruses, dengue, yellow fever, and Ilheus circulate only in subtropical areas of Argentina (the province of Cordoba is not included in this area); only dengue virus was investigated (by neutralization test) because of a current epidemiologic surveillance program; results were negative. No evidence that West Nile virus is currently circulating or has entered Argentina was found, so we did not perform tests to detect it (2,9). Isolation of SLEV from the cerebrospinal fluid and blood was attempted in newborn mice and Vero cell cultures with negative results. While the typical clinical manifestations of viral encephalitis (fever, headache, and altered level of consciousness) are indistinguishable from each other, tremor and other extrapyramidal signs are described in St. Louis encephalitis and Japanese encephalitis (10). The typical MRI finding of patients with St. Louis encephalitis is localized in the substantia nigra (11). In summary, the occurrence of St. Louis encephalitis in a 61-year-old patient, after >10 years of no reports in Argentina, along with specific epidemiology, suggest that further studies are needed to assess the risk for human infection by SLEV in Argentina and the role of several mosquitoes species in its transmission.

In response to the first human outbreak (January - May 2005) of Saint Louis encephalitis (SLE) virus in Córdoba province, Argentina, we developed an environmental SLE virus risk map for the capital, i.e. Córdoba city. The aim was to provide a map capable of detecting macro-environmental factors associated with the spatial distribution of SLE cases, based on remotely sensed data and a geographical information system. Vegetation, soil brightness, humidity status, distances to water-bodies and areas covered by vegetation were assessed based on pre-outbreak images provided by the Landsat 5TM satellite. A strong inverse relationship between the number of humans infected by SLEV and distance to high-vigor vegetation was noted. A statistical non-hierarchic decision tree model was constructed, based on environmental variables representing the areas surrounding patient residences. From this point of view, 18% of the city could be classified as being at high risk for SLEV infection, while 34% carried a low risk, or none at all. Taking the whole 2005 epidemic into account, 80% of the cases came from areas classified by the model as medium-high or high risk. Almost 46% of the cases were registered in high-risk areas, while there were no cases (0%) in areas affirmed as risk free. Fil: Rotela, Camilo Hugo. Comision Nacional de Actividades Espaciales; Argentina Fil: Spinsanti, Lorena Ivana. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología "Dr. J. M. Vanella"; Argentina Fil: Lamfri, Mario. Comision Nacional de Actividades Espaciales; Argentina Fil: Contigiani de Minio, Marta Silvia. Universidad Nacional de Córdoba. Facultad de Medicina. Instituto de Virología "Dr. J. M. Vanella"; Argentina Fil: Almiron, Walter Ricardo. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Centro de Investigaciones Entomológicas de Córdoba; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Investigaciones Biológicas y Tecnológicas. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Instituto de Investigaciones Biológicas y Tecnológicas; Argentina Fil: Scavuzzo, Carlos Marcelo. Comision Nacional de Actividades Espaciales; Argentina

To determine hepatitis C virus (HCV) genotypes circulating in the central region of Argentina, 96 consecutive anti-HCV positive subjects were studied. The presence of HCV RNA was detected in 60 samples by RT-nested PCR of the 5' noncoding region (5' NCR). Genotyping was performed by restriction fragment length polymorphism analysis of 5' NCR region combined with PCR using type-specific primers of the core region. The groups of individuals in this study included hemophilia and hemodialysis patients, injecting drug users, screened blood donors, and patients with acute or chronic liver disease, all from Córdoba, Argentina. Overall, genotype 2 was the most prevalent (55.0%), followed by genotypes 1 (38.3%), and 3 (5.0%). Within genotype 1, subtype 1b was the most prevalent. An unexpected high prevalence of genotype 2 (61.9%) was found among patients with acute or chronic HCV infection (without known risk factors). These figures differ from other cohorts from East-Argentina where genotype 1 has been found as the most prevalent. This indicates that regional differences of genotype distribution might exist between Central and East Argentina.

Una virus (UNAV), Togaviridae family, is widely distributed in South America, where infections have been detected in mosquitoes and vertebrate hosts (humans, birds and horses). We analyzed human sera from Córdoba inhabitants aged 44 to 89 years and using a neutralization test, we found a prevalence of UNAV antibodies of 3.8% (3/79). The low titers detected suggest past infections probably acquired in rural areas of the Province of Córdoba (central Argentina). None sera were found positive for MAYV neutralizing antibodies. This is the first report of human infections by UNAV in Argentina.

An in house indirect immmunofluorescence assay ( IFA ) in relation to neutralization (NT) reference test, was assessed as a fast and cheap method to carry out serological surveys for St. Louis Encephalitis virus (SLE). Sera obtained from 213 blood donors were analyzed by both tests. The prevalence of seropositivity obtained with IFA was lower than (30.98%) that observed on NT (41.78%). The relative specificity rate of IFA was 96.77% whereas its relative sensitivity rate was 69.66%. Kappa index showed a good correlation between both tests. The results indicate that neutralization assay is still the serological test with the highest sensitivity and specificity relative rates for detecting antibodies against SLE virus. Nevertheless, the IFA could be useful as an alternative test in order to learn the circulation of the Flavivirus genus in a certain area. Com a finalidade de dispor de um método rápido e de baixo custo para realizar estudos séricos dirigidos ao virus da encefalite St.Louis (ESL), avaliamos a técnica de imunofluorescência indireta (IFI) artesanal em relação ao teste referência de neutralização (NT). Examinaram-se 213 soros de doadores de sangue. A prevalência dos anticorpos obtidas na técnica de IFI (30,98%) foi mais baixa do que a pesquisada com NT (41,78%). A taxa de especificidade relativa da IFI foi 96,77%, enquanto sua taxa de sensibilidade relativa foi 69,66%. O índice Kappa demonstrou boa concordância entre os dois testes. Os resultados achados revelam que a NT continua sendo a técnica sorológica de maior taxa de especificidade e sensibilidade relativa para a detecção de anticorpos IgG para o vírus ESL. Contudo, a IFI poderia ser o teste de escolha em estudos da circulação desta arbovirose na população humana.