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.

The reintroduction of DENV-2 in 2011 in Panama and subsequent outbreak characteristic.

The circulation of the South-east Asian/American (AS/AM) dengue 2 virus (DENV-2) genotype in the Americas has been associated with a high rate of severe disease. From 1993, the year DENV was reintroduced in Panama, until 2011 there were 29 dengue-associated deaths, 17 of which occurred in 2011, the most severe outbreak with a case fatality rate (CFR) of 44% (17 deaths out of 38 severe dengue cases). During this outbreak DENV-2 was reintroduced into the country, whereas over the prior five years DENV-1 and -3 were predominant. Herein, we describe the 2011 Panama outbreak and genetically characterize the Panamanian DENV-2 strains, which were associated with severe dengue disease in Panama. Our results suggest that the DENV-2 isolates from this outbreak belonged to the AS/AM genotype sub-clade 2BI and were genetically close to viruses described in the outbreaks in Nicaragua, Honduras, Guatemala and Mexico from 2006-2011. Sub-clade 2BI has previously been associated with severe disease in Nicaragua during outbreaks from 2005-2007.

Genetic relationships among Mayaro and Una viruses suggest distinct patterns of transmission.

Mayaro and Una viruses (MAYV, UNAV) are mosquito-borne alphaviruses that may cause an acute febrile illness characterized by headache, retro-orbital pain, and rash that may progress to a severe and prolonged arthralgia. MAYV was first isolated in Trinidad in 1954, and UNAV was first identified in northern Brazil in 1959. Since then, numerous isolates of these agents have been made from humans, wild vertebrates, and mosquitoes in several countries in northern South America. Serological evidence suggests that these viruses are also present in portions of Central America. Because little is known about the natural transmission cycle of MAYV and virtually nothing is known about UNAV transmission, 63 isolates covering the known geographic and temporal ranges were used in phylogenetic analyses to aid in understanding the molecular epidemiology. Approximately 2 kb from the E1 and E2 glycoprotein genes and the complete 3' non-coding region were sequenced. Phylogenetic analyses of these sequences indicated that two distinct genotypes of MAYV exist with a distinct clade consisting exclusively of UNAV (previously designated as a subtype of MAYV). One MAYV genotype (genotype D) contains isolates from Trinidad and the northcentral portion of South America including Peru, French Guiana, Surinam, Brazil, and Bolivia. All of these isolates are highly conserved with a nucleotide divergence of < 6%. The second MAYV genotype (genotype L) contains isolates only from Brazil that are highly conserved (< 4% nucleotide divergence) but are quite distinct (15-19%) from the first genotype isolates. These analyses provide possible explanations for the natural ecology and transmission of MAYV and UNAV.

SEROSURVEY OF SELECTED ARBOVIRAL PATHOGENS IN FREE-RANGING, TWO-TOED SLOTHS (CHOLOEPUS HOFFMANNI) AND THREE-TOED SLOTHS (BRADYPUS VARIEGATUS) IN COSTA RICA, 2005-07.

We screened for antibodies to 16 arboviruses in four populations of free-ranging sloths in Costa Rica. Blood samples were taken from 16 Hoffman's two-toed sloths (HTSs; Choloepus hoffmanni ) and 26 brown-throated sloths (BTSs; Bradypus variegatus ) over a 3-yr period. We used serologic assays to detect antibodies against 10 arboviruses previously described in sloths (St. Louis encephalitis [SLEV], Changuinola, Venezuelan equine encephalitis, Ilheus [ILHV], Oropouche, Mayaro, Utinga, Murutucu, Punta Toro, and vesicular stomatitis [VSV] viruses) and six arboviruses not described in sloths (Rio Grande, West Nile [WNV], eastern equine encephalitis, Piry, Munguba, and La Crosse viruses). Overall, 80% of sloths had detectable antibodies to SLEV, 67% had antibodies to ILHV, 32% to Punta Toro virus, 30% to Changuinola virus, 15% to WNV, 14% to VSV, 11% to Venezuelan equine encephalitis virus, and 10% to Rio Grande virus. No samples had detectable antibodies to the remaining eight viruses. We found a significant increase in prevalence of antibody to VSV in HTSs between 2005 and 2007, and for WNV antibody between 2005 and 2006. We found no significant differences in the prevalences of antibodies to the sampled viruses between the two locations. Antibody prevalences were significantly higher in HTSs than in BTSs for SLEV in 2005. Antibody-positive results for ILHV were likely due to cross-reaction with SLEV. The novel finding of antibodies to Rio Grande virus in sloths could be due to cross-reaction with another phlebovirus. These findings might have implications for land management and domestic animal health. Due to the nature of the study, we could not determine whether sloths could represent amplification hosts for these viruses, or whether they were only exposed and could be used as sentinel species. Further studies are needed to fully characterize arboviral exposure in sloths.

Massilia virus, a novel Phlebovirus (Bunyaviridae) isolated from sandflies in the Mediterranean.

A new virus was isolated from three independent pools of Phlebotomus perniciosus sandflies (Diptera; Psychodidae) trapped in two regions of southeastern France, located 90 miles apart. Microscopic, antigenic and genetic analyses indicate that this novel virus belongs to the genus Phlebovirus in the family Bunyaviridae. The new virus is designated Massilia virus since the first isolate was obtained from sandflies collected in the suburban area of Marseille. The complete genome sequence was determined and used to compare the genetic and phylogenetic relationships of Massilia virus with other phleboviruses. Genetic and antigenic properties were employed to address whether or not Massilia virus should be considered a new species within the genus, or a member of a previously recognized species. Cerebrospinal fluid specimens, collected from local patients with central nervous system infections during the previous four-year period were tested for the presence of Massilia virus RNA, but gave negative results. In conclusion, Massilia virus is proposed as a member of the Sandfly fever Naples virus complex; its public health importance has yet to be determined.

Identificaçäo do vírus causador da encefalomielite eqüina, Paraná, Brasil / Identification of the encephalitis equine virus, Brazil

Objetivo: No período de 1996 a 1999, um agente viral causador de encefalomielite afetou as populaçöes de eqüinos em diferentes regiöes do Estado do Paraná, Brasil. Objetivou-se realizar pesquisa sorológica na tentativa de isolar o vírus causador da doença. Métodos: Em quatro municípios do Estado do Paraná, Brasil, foram coletados culicídeos com armadilha Shannon e isca humana, identificados e processados para isolamento de vírus. Em dois municípios estudados foram colhidas amostras de sangue de eqüinos para isolamento de vírus e para pesquisa sorológica. Os soros foram analisados pelo teste de inibiçäo da hemaglutinaçäo frente a diferentes antígenos de Alphavirus e Flavivirus. Aqueles que revelaram reaçöes positivas-cruzadas foram analisados pelo teste de neutralizaçäo. Resultados: Foram coletados culicídeos dos gêneros: Culex, Aedes, Mansonia, Coquillettidia, Psorophora, Sabethes, Wyeomyia e Limatus. Embora näo sendo isolado o agente viral, foram detectados anticorpos hemaglutinantes para o vírus Encefalomielite eqüina do Leste, Mucambo, Pixuna, Maguari e St. Luis. Em doze amostras de soros foram detectados anticorpos neutralizantes para o vírus Encefalomielite eqüina do Leste. Conclusöes: Foram coletadas espécies de culicídeos, considerados na bibliografia como vetores de vírus causadores de encefalomielite buniavírus e outras arboviroses de importância epidemiológica. Pela presença de sintomas de encefalomielite e de anticorpos para o vírus Encefalomielite eqüina do Leste nos soros de cavalos, supöe-se ser esse o vírus causador da doença nos eqüinos das regiöes estudadas