Dengue epidemics in two distinct periods reveal distinct epidemiological, laboratorial and clinical aspects in a same scenario: analysis of the 2010 and 2013 epidemics in Mato Grosso do Sul, Brazil.

BACKGROUND: Dengue is a major problem in Brazil. Epidemiological and clinical aspects were characterized in patients from two epidemics which occurred in Mato Grosso do Sul, Brazil. METHODS: Dengue cases were classified according to the 2009 WHO criteria, tested by serological and molecular biology tests and analysed for nonstructural protein 1 (NS1) antigenemia. RESULTS: Dengue was confirmed in 78.7% (48/61) and 75.6% (118/156) of the cases studied in 2010 and 2013, respectively. DENV-1 and DENV-2 were the serotypes involved in the 2010 epidemic and DENV-4 in the 2013 one. Most of the cases were classified as dengue without warning; however, severe dengue was observed in 18.7% (9/48) of the cases in 2010 and less observed in DENV-4 cases. NS1 levels were higher in patients with dengue with warning signs and severe dengue in 2010. Circulating aspartate aminotransferase (AST) and alanine transferase (ALT) were altered in all groups, independently of the infecting serotype or epidemic. Patients with DENV-1 and DENV-2 presented significant lower monocyte counts when compared to patients with DENV-4. An inverse correlation was found between platelet count, leucocytes, monocytes and NS1 levels. CONCLUSIONS: Epidemics caused by the prevalence of distinct DENV serotypes had different impacts and clinical characteristics in a same scenario and, despite the occurrence of secondary infections, the DENV-4 emergence was not associated with severe cases.

Insights of the genetic diversity of DENV-1 detected in Brazil in 25 years: Analysis of the envelope domain III allows lineages characterization.

Dengue virus type 1 (DENV-1) was first isolated in Brazil in 1986 in the state of Rio de Janeiro (RJ) and during 25years, this serotype emerged and re-emerged causing explosive epidemics in the country. Here, we aimed to present the phylogeny and molecular characterization based on the envelope gene (E) of DENV-1 (n=48) isolated during epidemics occurred from 1986 to 2011. Six full coding region genomes of DENV-1 were fully sequenced and possible genomic recombination events were analyzed. The results showed that the Brazilian DENV-1 isolates analyzed belong to genotype V (Americas/Africa), but grouping into distinct clades. Three groups were identified, one dating from 1986 to 2002 (lineage 1a), a second group isolated from 2009 to 2011 and a representative strain isolated in 2002 (lineage 2), and a group of strains isolated from 2010 to 2011 (lineage 1b). The lineages 1a and 1b were more closely related to the American strains, while lineage 2 to the Asian strains. Amino acids (aa) substitutions were observed in the domains I and III of the E protein and were associated to the lineages segregation. A substitution on E297 differentiated the lineage 1a from the lineages 1b and 2. Substitutions on E338, E394 (domain III), E428 and E436 (stem region) differentiated lineages 1a, 1b and 2. With the exception of the C gene, all the others genes analyzed allowed the DENV-1 classification into the distinct genotypes. Interestingly, the E gene's domain III and stem regions alone were able to characterize the distinct lineages, as observed by the analysis of the entire E gene and the complete coding region. No recombinant events were detected, but a strain belonging to lineage 1a was closely related to a known recombinant strain (AF513110/BR/2001).

Twenty years of DENV-2 activity in Brazil: molecular characterization and phylogeny of strains isolated from 1990 to 2010.

In Brazil, dengue has been a major public health problem since its introduction in the 1980s. Phylogenetic studies constitute a valuable tool to monitor the introduction and spread of viruses as well as to predict the potential epidemiological consequences of such events. Aiming to perform the molecular characterization and phylogenetic analysis of DENV-2 during twenty years of viral activity in the country, viral strains isolated from patients presenting different disease manifestations (n = 34), representing six states of the country, from 1990 to 2010, were sequenced. Partial genome sequencing (genes C/prM/M/E) was performed in 25 DENV-2 strains and full-length genome sequencing (coding region) was performed in 9 strains. The percentage of similarity among the DENV-2 strains in this study and reference strains available in Genbank identified two groups epidemiologically distinct: one represented by strains isolated from 1990 to 2003 and one from strains isolated from 2007 to 2010. No consistent differences were observed on the E gene from strains isolated from cases with different clinical manifestations analyzed, suggesting that if the disease severity has a genetic origin, it is not only due to the differences observed on the E gene. The results obtained by the DENV-2 full-length genome sequencing did not point out consistent differences related to a more severe disease either. The analysis based on the partial and/or complete genome sequencing has characterized the Brazilian DENV-2 strains as belonging to the Southeast Asian genotype, however a distinction of two Lineages within this genotype has been identified. It was established that strains circulating prior DENV-2 emergence (1990-2003) belong to Southeast Asian genotype, Lineage I and strains isolated after DENV-2 emergence in 2007 belong to Southeast Asian genotype, Lineage II. Furthermore, all DENV-2 strains analyzed presented an asparagine (N) in E390, previously identified as a probable genetic marker of virulence observed in DHF strains from Asian origin. The percentage of identity of the latter with the Dominican Republic strain isolated in 2001 combined to the percentage of divergence with the strains first introduced in the country in the 1990s suggests that those viruses did not evolve locally but were due to a new viral Lineage introduction in the country from the Caribbean.

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 Simplexa™ 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 10(3) copies/mL of virus, as determined by quantitative real-time RT-PCR. This is the first time the Simplexa™ 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 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.