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BACKGROUND/OBJECTIVES:Understanding the factors underlying the spatio-temporal distribution of infectious diseases provides useful information regarding their prevention and control. Dengue fever spatio-temporal patterns result from complex interactions between the virus, the host, and the vector. These interactions can be influenced by environmental conditions. Our objectives were to analyse dengue fever spatial distribution over New Caledonia during epidemic years, to identify some of the main underlying factors, and to predict the spatial evolution of dengue fever under changing climatic conditions, at the 2100 horizon. METHODS:We used principal component analysis and support vector machines to analyse and model the influence of climate and socio-economic variables on the mean spatial distribution of 24,272 dengue cases reported from 1995 to 2012 in thirty-three communes of New Caledonia. We then modelled and estimated the future evolution of dengue incidence rates using a regional downscaling of future climate projections. RESULTS:The spatial distribution of dengue fever cases is highly heterogeneous. The variables most associated with this observed heterogeneity are the mean temperature, the mean number of people per premise, and the mean percentage of unemployed people, a variable highly correlated with people's way of life. Rainfall does not seem to play an important role in the spatial distribution of dengue cases during epidemics. By the end of the 21st century, if temperature increases by approximately 3 °C, mean incidence rates during epidemics could double. CONCLUSION:In New Caledonia, a subtropical insular environment, both temperature and socio-economic conditions are influencing the spatial spread of dengue fever. Extension of this study to other countries worldwide should improve the knowledge about climate influence on dengue burden and about the complex interplay between different factors. This study presents a methodology that can be used as a step by step guide to model dengue spatial heterogeneity in other countries.

BACKGROUND: Dengue dynamics are driven by complex interactions between human-hosts, mosquito-vectors and viruses that are influenced by environmental and climatic factors. The objectives of this study were to analyze and model the relationships between climate, Aedes aegypti vectors and dengue outbreaks in Noumea (New Caledonia), and to provide an early warning system. METHODOLOGY/PRINCIPAL FINDINGS: Epidemiological and meteorological data were analyzed from 1971 to 2010 in Noumea. Entomological surveillance indices were available from March 2000 to December 2009. During epidemic years, the distribution of dengue cases was highly seasonal. The epidemic peak (March-April) lagged the warmest temperature by 1-2 months and was in phase with maximum precipitations, relative humidity and entomological indices. Significant inter-annual correlations were observed between the risk of outbreak and summertime temperature, precipitations or relative humidity but not ENSO. Climate-based multivariate non-linear models were developed to estimate the yearly risk of dengue outbreak in Noumea. The best explicative meteorological variables were the number of days with maximal temperature exceeding 32°C during January-February-March and the number of days with maximal relative humidity exceeding 95% during January. The best predictive variables were the maximal temperature in December and maximal relative humidity during October-November-December of the previous year. For a probability of dengue outbreak above 65% in leave-one-out cross validation, the explicative model predicted 94% of the epidemic years and 79% of the non epidemic years, and the predictive model 79% and 65%, respectively. CONCLUSIONS/SIGNIFICANCE: The epidemic dynamics of dengue in Noumea were essentially driven by climate during the last forty years. Specific conditions based on maximal temperature and relative humidity thresholds were determinant in outbreaks occurrence. Their persistence was also crucial. An operational model that will enable health authorities to anticipate the outbreak risk was successfully developed. Similar models may be developed to improve dengue management in other countries.

Registramos a ocorrência de epidemia de dengue causada pelo sorotipo 2 (DEN 2) na cidade de Araguaina, estado do Tocantins (TO) situado no Brasil central. Quatrocentos indíviduos de 74 famílias, residentes nos bairros S. João, Araguaina Sul e Neblina foram entrevistados e sangrados, independentemente de terem adoecido ou não. Os soros tanto de adultos quanto de crianças de ambos os sexos foram usados para pesquisa de anticorpos inibidores da hemaglutinação (IH) e IgM através de ensaio imunoenzimático (MAC ELISA). Nas casas onde haviam doentes no momento do inquérito, sangue total também foi colhido para tentativa de isolamento de vírus. O quadro clínico apresentado pelos pacientes foi caracterizado por febre, cefaléia, mialgias, artralgias e exantema do tipo máculo-papular não pruriginoso. A infecção foi mais frequente em mulheres (33.9%) do que nos homens (23.8%), ocorrendo em todas as faixas etárias, inclusive em crianças com menos de um ano de idade, bem como em maiores de 70 anos. Um total de 1105 mosquitos (56 fêmeas e 45 machos de Culex quinquefasciatus e 567 fêmeas e 437 machos de Aedes aegypti) foram obtidos a partir de larvas coletadas em Araguaina. As fêmeas de Ae. aegypti obtidas das larvas fizeram repasto sangüíneo em 8 pacientes febris. O diagnóstico laboratorial foi feito por isolamento de vírus (cultura de células de Aedes albopictus, clone C6/36) e por sorologia (IH e MAC ELISA). Foram isoladas 5 amostras de DEN 2 de pacientes febris e tipadas por imunofluorescência indireta usando anticorpos monoclonais de dengue. Nenhuma amostra viral foi isolada de mosquitos. Outrossim, comprovou-se infecção em 111 pessoas sangradas, o que revelou um índice de positividade de 27.75% (111 em 400), sendo que 66.2% das famílias estudadas apresentaram pelo menos um indivíduo positivo. Ocorreram ainda, 26.1% de infecções assintomáti-cas. Por outro lado, a correlação de positividade entre os dois testes usados (IH e MAC ELISA) foi de 94.6%. Estimamos que ocorreram aproximadamente 83.250 casos da doença, entre 15 de março a 31 de maio de 1991. Esta é a primeira epidemia de DEN 2 em um estado da Amazônia Brasileira, portanto em área endêmica de febre amarela, e a primeira evidência da interiorização do DEN 2, até então restrito ao Rio de Janeiro.We report the first outbreak of dengue fever caused by dengue 2 (DEN 2) in Araguaina, Tocantins State. Four hundred people of 74 families, living at S. João, Araguaina Sul and Neblina districts were questioned and then bled, in order to obtain sera to test for anti-dengue antibodies. If a person was sick, a small quantity of blood was collected for virus isolation. The main clinical picture of disease was characterized by fever, headache, myalgias, arthralgias and skin rash. Were obtained 1,105 (56 females and 45 males of Culex quinquefasciatus and 567 females and 437 males of Aedes aegypti) mosquitoes from larvae collected in Araguaina. The females of Aedes aegypti obtained from larvae were allowed to feed on 8 febrile patients. The diagnosis of infection was made by both virus isolation into Aedes albopictus (C6/36) cells, and serology, by Hemagglutination-inhibi-tion (HI) and IgM capture ELISA (MAC ELISA). No virus was isolated from mosquitoes. Although five strains of DEN 2 were obtained from humans, and another 111 infections were diagnosed sero-logically (IgM positive). The positivity rate of the samples was 27.75% (111 of 400), while that of the families was 66.2% (45 of 72), where at least one member of the each family was infected. It was also detected 26.1% of asymptomatic infections. All age groups were affected. Therefore, the infection was more frequent in females (33.5%) than males (23.8%). It was estimated in about 83,250 cases of dengue infection in Araguaina between March 15 and May 31,1991. This is the first epidemic of DEN 2 in the Brazilian Amazonian region, as well as the first evidence of the spread of this serotype outside Rio de Janeiro.

Os autores revêem os aspectos ecoepidemiológicos apresentados pelos virus da encefalite de St. Louis (SLE), encefalites equinas Leste (EEE), Oeste (WEE) e Venezuelana [subtipos III, Mucambo (MUC) e IV, Pixuna (PIX)], decorrentes dos estudos realizados em diversas áreas da Região Amazônica brasileira, especialmente ao longo das rodovias e projetos de desenvolvimento. Esses vírus são amplamente distribuídos na Amazônia e pelo menos quatro deles, EEE, WEE, MUC e SLE já demonstraram ser patógenos do homem. O diagnóstico da doença humana foi feito por sorologia, sendo que de MUC e SLE obteve-se também isolamento viral. O vírus PIX, parece ser o menos prevalente e foi isolado em poucas oportunidades. Virtualmente se desconhecem os vetores do PIX e WEE. As aves silvestres constituem os hospedeiros principais de todos esses vírus, exceto do MUC, para o qual constituem os roedores. O quadro clínico apresentado pelos pacientes infectados na Amazônia é discutido, comparando-o ao apresentado em outras áreas, especialmente nos EUA, onde periodicamente SLE, EEE e WEE causam surtos de doença humana. Nenhuma epidemia foi até o presente detectada, embora em 1960 uma epizootia em eqüinos causada pelo EEE tenha sido registrada em Bragança, Pará, onde em um rebanho de 500 animais ocorreu uma letalidade de 5%. Quatro outras pequenas epizootias determinadas pelo SLE ocorreram nas florestas adjacentes a Belém, envolvendo aves silvestres e animais sentinelas.An overview of ecological, epidemiological and clinical findings of potential arthropod-borne encephalitis viruses circulating in the Amazon Region of Brazil are discussed. These viruses are the Eastern Equine Encephalitis (EEE), Western Equine Encephalitis (WEE), St. Louis Encephalitis (SLE), Mucambo (MUC) and Pixuna (PIX). These last two are subtypes (HI and IV) of Venezuelan Equine Encephalitis virus. The areas of study were the highways and projects of development, as well as places where outbreaks of human diseases caused by arboviruses had been detected. These viruses are widespread in all Amazonia, and at least four of them, EEE, WEE, SLE and MUC are pathogenic to man. EEE and WEE infections were detected by serology, while SLE and MUC by either serology and virus isolation. The PIX virus has the lowest prevalence and, it was isolated in only a few cases, one being from a laboratory infection. Wild birds are the main hosts for all these viruses, except MUC, whose major hosts are rodents. The symptoms presented by infected people were generally a mild febrile illness. Although, jaundice was observed in two individuals from whom SLE was isolated. A comparison of the clinical symptoms presented by the patients in the Amazon Region and other areas of America, especially in the USA is made. In Brazilian Amazon region epidemics have not been detected although, at least, one EEE epizootic was recorded in Bragança, Para State, in 1960. At that time, of 500 horses that were examined 61% were positive to EEE by HI and of mem 8.2% died On the other hand. SLE has caused four epizootics in a forest near Belem. Wild birds and sentinel monkeys were infected, but no human cases were reported.

Os autores descrevem a ocorrência de epidemias causadas pelo vírus Oropouche (ORO) nos Estados do Maranhão (MA) e Goiás (GO) em 1988. 36 amostras de vírus foram obtidas a partir da inoculação do sangue de 120 pacientes em camundongos recém nascidos. A doença foi caracterizada por febre, cefaléia, dores musculares, articulares, fotofobia, dor retro ocular, náuseas e tontura. 128 das 197 pessoas examinadas em Porto Franco, MA, tinham anticorpos inibidores da hemaglutinação (IH) para o agente e, em 106 foram detectados anticorpos IgM por MAC ELISA. Todos os grupos etários foram infectados, embora a incidência tenha sido mais elevada entre aqueles com 10 a 19 anos de idade. Quanto ao sexo, a infecção ocorreu igualmente em ambos os sexos. Recorrência dos sintomas foi observada em 56% dos casos positivos estudados. A inoculação em camundongos Swiss recém nascidos de 3.624 Culicoides paraensis (Ceratopogonidae) e 1.970 Culex (Culex) quinquefasciatus (Culicidae), coletados em Porto Franco-MA, resultou em um único isolamento do vírus ORO a partir dos Culicoides. Essa é a primeira descrição de casos confirmados de infecção pelo vírus Oropouche nos Estados do Maranhão e Goiás, Brasil.