Adrián Farías

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 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.

Human outbreak of St. Louis encephalitis detected in Argentina, 2005

BACKGROUND An outbreak of flavivirus encephalitis occurred in 2005 in Córdoba province, Argentina. OBJECTIVES To characterize the epidemiologic and clinical features of that outbreak and provide the serologic results that identified St. Louis encephalitis virus (SLEV) as the etiologic agent. STUDY DESIGN From January to May 2005, patients with symptoms of encephalitis, meningitis, or fever with severe headache were evaluated and an etiologic diagnosis achieved by detection of flavivirus-specific antibody sera and cerebrospinal fluid. RESULTS The epidemic curve of 47 cases showed an explosive outbreak starting in January 2005 with one peak in mid-February and a second peak in mid-March; the epidemic ended in May. Cases occurred predominantly among persons 60 years and older. Nine deaths were reported. SLEV antibodies, when detected in 47 patients studied, had a pattern characteristic of a primary SLEV infection. CONCLUSIONS Even though isolated cases of St. Louis encephalitis have been reported in Argentina, this is the first description of a large SLEV encephalitis outbreak in Argentina.

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.

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.

Hepatitis C and HIV coinfection in central region of Argentina: prevalence, genotype characterization and risk factors

BACKGROUND This is the first study reporting the epidemiological and molecular characterization of HCV/HIV coinfection in the central region of Argentina. METHOD Cross-sectional, epidemiological study (2003-2004). STATISTICS multivariate logistic regression analysis. RESULTS The incidence of HCV/HIV coinfection was 12.3%. HCV genotype 1 was the most prevalent (73%). Intravenous drug use was the main independent risk factor for acquiring HCV infection. However, an alternative route (sexual) for viral transmission was suggested. CONCLUSIONS These results underscore the potential public health impact of HCV/HIV coinfection in our region.

Cocirculation of Rio Negro Virus (RNV) and Pixuna Virus (PIXV) in Tucuman province, Argentina

Venezuelan equine encephalitis complex includes viruses considered emerging pathogens for humans and animals in the Americas. Two members of this complex have been detected previously in Argentina: Rio Negro Virus (RNV), detected in mosquitoes from Chaco province and rodents from Formosa province, and Pixuna Virus (PIXV), detected in mosquitoes from Chaco province. To carry out surveillance studies in other parts of the country, detection of a 195‐bp fragment of alphaviruses by RT‐nested PCR was performed in mosquito samples from San Miguel de Tucumán city. Four pools resulted positive and three were sequenced. Two amplicons grouped with RNV and one with PIXV. This is the first report of viral activity of members of the Venezuelan equine encephalitis complex in north‐eastern Argentina.

Molecular identification of human enteroviruses in children with neurological infections from the central region of Argentina

In the central area of Argentina, epidemiological and molecular characteristics of human enterovirus infections are still unknown. RT-nested PCR of the highly conserved 5′NCR was used to detect enteroviruses in 168 samples of cerebrospinal fluid from hospitalized patients with suspected infection of the central nervous system (2007–2008), and 13 (7.7%) were positive. Molecular typing was performed by sequencing of the 3′-half VP1 region. Echovirus 30 was the predominant type detected, followed by coxsackie viruses A9 and B4. All echovirus 30 strains of 2007 clustered in lineage H, whereas the echovirus 30 isolate obtained in 2008 was more distantly related, possibly representing a new lineage.

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

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

Determinants of immunological and virological responses to antiretroviral therapy amongst HIV-infected adults in central Argentina: negative influence of hepatitis C infection

BACKGROUND The purpose of this study was to update the epidemiological data on the prevalence of coinfection with hepatitis C virus (HCV) and HIV, and to identify whether specific clinical and epidemiological factors influenced the response of HIV-positive adults to highly active antiretroviral therapy (HAART). METHODS This retrospective observational cohort study of 238 HIV-infected patients evaluated the effect of different epidemiological and clinical parameters (including HCV coinfection) on therapy response among HIV-infected adults initiating HAART. Multiple logistic regression models were used to identify factors associated with therapy response and estimated risk coefficients. RESULTS Seroprevalence of HCV infection in this population was 26% (62/238). We did not observe a significant association between immunological or virological response relating to patient gender or HAART regimen. However, this analysis showed that HCV serological status, age at HIV diagnosis, duration of treatment and WHO clinical stage of AIDS (<200 CD4 cells/ml independently of viral load either < or > to 100,000 copies/ml), were significantly associated with immunological and virological responses to HAART. CONCLUSIONS These results show further evidence that hepatitis C serostatus is associated with a reduced response to HAART.

Immunoglobulin G subclasses in antibody responses to St. Louis encephalitis virus infections

The aim of this study was to recognize the specific antiviral response patterns of IgG1, IgG2, IgG3 and IgG4 subclasses, elicited during St. Louis encephalitis virus (SLEV) infection in humans. Eighty-five samples of human sera from 44 patients with SLEV infection were obtained between days 1 and 365 or later, after onset of the disease. These samples were processed by immunofluorescence assay for detection of IgG1-, IgG2-, IgG3- and IgG4-specific antibodies. We demonstrate the presence of all isotypes of IgG for more than a year in patients infected with SLEV. However; isotype IgG1 was present at the highest titers, with a peak between days 8 and 30 after onset of the disease.