Dengue 4 in Ceará, Brazil: characterisation of epidemiological and laboratorial aspects and causes of death during the first epidemic in the state

BACKGROUND The first dengue cases in Brazil with laboratory confirmation occurred in the northern region of the country, with the isolation of two serotypes, dengue virus 1 (DENV-1) and DENV-4. In Ceará, the introduction of DENV-4 was reported during a DENV-1 epidemic in 2011, with only two isolations. OBJECTIVES The aim of this study was to characterise the first DENV-4 epidemic in the state of Ceará, Brazil. METHODS The study population was composed of patients with suspected dengue that were reported to health care units from January to December 2012. The laboratory confirmation of infection was made by viral isolation, reverse transcription polymerase chain reaction (RT-PCR), AgNS1, immunohistochemistry and IgM enzyme-linked immunosorbent assay (ELISA). MAIN CONCLUSIONS In the study year, 72,211 suspected dengue cases were reported and 51,865 of these cases (71.8%) were confirmed to be positive. Co-circulation of three serotypes, DENV-1, DENV-3 and DENV-4, was detected with a predominance of DENV-4 (95.3%). Most cases were not severe, but there were 44 fatal outcomes. DENV-4 Genotype II was identified for the first time in Ceará.

Dengue virus type 4 in Niterói, Rio de Janeiro: the role of molecular techniques in laboratory diagnosis and entomological surveillance

In Niterói, state of Rio de Janeiro, dengue virus type 4 (DENV-4) was isolated for the first time in March 2011. We analysed the laboratory findings of the first cases and evaluated the use of molecular techniques for the detection of DENV-4 in Aedes aegypti that were field-caught. Conventional reverse transcriptase-polymerase chain reaction (RT-PCR) and SimplexaTM Dengue real-time RT-PCR confirmed DENV-4 infection in all cases. Additionally, DENV-4 was confirmed in a female Ae. aegypti with 1.08 x 10³ copies/mL of virus, as determined by quantitative real-time RT-PCR. This is the first time the SimplexaTM Dengue real-time assay has been used for the classification of cases of infection and for entomological investigations. The use of these molecular techniques was shown to be important for the surveillance of dengue in humans and vectors.

Dengue virus type 3 in Brazil: a phylogenetic perspective

Circulation of a new dengue virus (DENV)-3 genotype was recently described in Brazil and Colombia, but the precise classification of this genotype has been controversial. Here we perform phylogenetic and nucleotide-distance analyses of the envelope gene, which support the subdivision of DENV-3 strains into five distinct genotypes (GI to GV) and confirm the classification of the new South American genotype as GV. The extremely low genetic distances between Brazilian GV strains and the prototype Philippines/L11423 GV strain isolated in 1956 raise important questions regarding the origin of GV in South America.

Complete genetic characterization of a Brazilian dengue virus type 3 strain isolated from a fatal outcome

We have determined the complete nucleotide and the deduced amino acid sequences of Brazilian dengue virus type 3 (DENV-3) from a dengue case with fatal outcome, which occurred during an epidemic in the state of Rio de Janeiro, Brazil, in 2002. This constitutes the first complete genetic characterization of a Brazilian DENV-3 strain since its introduction into the country in 2001. DENV-3 was responsible for the most severe dengue epidemic in the state, based on the highest number of reported cases and on the severity of clinical manifestations and deaths reported.

Obtenção, caracterização e utilização de polipeptídeos recombinantes de vírus dengue tipo 2 no diagnóstico das infecções por dengue / Attainment, characterization and use of recombinant polypeptides of dengue viruses type 2 in the diagnosis of dengue infections

Com o objetivo de se produzir antígenos recombinantes para o diagnóstico sorológico das infecções por vírus dengue (DENV), foi realizado o sequenciamento completo de uma cepa Brasileira (BR64022/98) de DENV-2 pela amplificação de segmentos contínuos, de aproximadamente 500pb, ao longo de todo o genoma viral. Vinte fragmentos amplificados por RT-PCR foram clonados e as sequências de nucleotídeos e de aminoácidos determinadas, resultando na primeira caracterização genética completa de uma cepa de DENV-2 do Brasil. Em uma segunda etapa, os fragmentos clonados foram expressos em Escherichia coli e purificados por cromatografia de afinidade. A reatividade dos polipeptídeos expressos e purificados aos anticorpos IgG anti-DENV presentes em soros humanos foi analisada por Western Blot e Enzyme Linked Immunosorbent Assay (ELISA). O polipeptídeo pD2-3 (E), localizado na porção N-terminal da proteína de envelope (E), apresentou maior reatividade quando utilizado na sua forma nativa, sendo reconhecido por 88 por cento dos soros testados e, consequentemente identificado como um antígeno candidato para utilização no diagnóstico das infecções pelos DENV. Soros de pacientes com febre amarela apresentaram ausência ou baixa reatividade contra pD2-3 (E). O pD2-3 (E) não foi reconhecido como antígeno recombinante sorotipo-específico, sendo reativo com soros de pacientes infectados por DENV-1, DENV-2 e DENV-3, com sensibilidade variando de 76,2 por cento a 93,3 por cento, nestes grupos específicos. O teste imunoenzimático indireto para a detecção de anticorpos IgG utilizando o pD2-3 (E) (REC IgG-ELISA) apresentou 89,1 por cento de sensibilidade e 96,4 por cento de especificidade, com maior sensibilidade para a confirmação de casos secundário s(98,1 por cento) quando comparados com casos primários de infecção por dengue (77,5 por cento). A não detecção de anticorpos IgG anti-DENV residuais pelo pD2-3(E) foi significante e demonstrou que um resultado reativo por REC IgG-ELISA é indicativo de infecção ativa por DENV. O REC IgG-ELISA tende a ser formatado como um teste qualitativo, dispensando a abordagem convencional de análises de títulos de IgG para a confirmação de infecções por DENV.

Complete nucleotide sequence analysis of a Brazilian dengue virus type 2 strain

In the last decade, dengue fever (DF) in Brazil has been recognized as an important public health problem, and an increasing number of dengue haemorrhagic fever (DHF) cases have been reported since the introduction of dengue virus type 2 (DEN-2) into the country in 1990. In order to analyze the complete genome sequence of a DEN-2 Brazilian strain (BR64022/98), we designed primers to amplify contiguous segments of approximately 500 base pairs across the entire sequence of the viral genome. Twenty fragments amplified by reverse transcriptase-PCR were cloned, and the complete nucleotide and the deduced amino acid sequences were determined. This constitutes the first complete genetic characterization of a DEN-2 strain from Brazil. All amino acid changes differentiating strains related to the Asian/American-Asian genotype were observed in BR64022/98, indicating the Asiatic origin of the strain

Dengue in the State of Rio de Janeiro, Brazil, 1986-1998

This paper presents epidemiological, laboratory, and clinical data on 12 years of dengue virus activity in the State of Rio de Janeiro from the time the disease was first confirmed virologically in April 1986 through April 1998. DEN-1 and DEN-2 viruses are the serotypes circulating in the state and were responsible for the epidemics reported during the last 12 years. The results published here show both the impact of dengue virus infections on the population and laboratory advances that have improved dengue diagnosis.

Diagnosis of dengue by using reverse transcriptase-polymerase chain reaction

A rapid identification of dengue viruses from clinical samples by using a nested reverse transcriptase-polymerase chain reaction (RT-PCR) procedure was carried out for diagnostic and epidemiological purposes. RT-PCR identified DEN-1 and DEN-2 viruses in 41 per cent (41/100) of previously confirmed cases and provided an accurate confirmation of DHF in four fatal cases. RT-PCR was also useful for detecting and typing dengue viruses in suspected cases, allowing a rapid identification of new serotypes in endemic areas.