Origin, tempo, and mode of the spread of DENV-4 Genotype IIB across the state of São Paulo, Brazil during the 2012-2013 outbreak

BACKGROUND Dengue virus type 4 (DENV-4) was first reported in Brazil in 1982 and since then no more cases were detected again in Brazil until 2010, when the virus was reintroduced. Over the following years, the virus spread to several Brazilian states and resulted in about 1,400,000 dengue cases, in 2013. The largest number of cases were documented in the Southeast macro-region. OBJECTIVES To determine the phylogeography of DENV-4 Genotype IIB strains isolated during the epidemics in 2012-2013 in São Paulo, Brazil, we aimed to contextualise the contribution of viruses sampled in different localities across the overall movement of DENV-4 in Brazil. METHODS Based on the envelope gene sequences retrieved from GenBank, we employed a Bayesian phylogeographic approach to assess the spatiotemporal dynamics of DENV-4 Genotype IIB in São Paulo, Brazil. FINDINGS The dispersal dynamics of DENV-4 Genotype IIB in Brazil indicated Rio de Janeiro and Mato Grosso states as the most likely routes toward São Paulo before the 2012-2013 outbreak. Likewise, Guarujá and São José do Rio Preto facilitated viral spread and transmission to other localities in the South and Southeast macro-regions in Brazil. CONCLUSIONS The spread pattern of DENV-4 Genotype IIB strains across the country supports two independent introductions of the virus in São Paulo in a short period of time. Furthermore, São Paulo appears to have played a pivotal role in the dissemination of DENV-4 to other locations in Brazil.

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.

Detection of dengue virus 4 from central India.

Background & objectives: Dengue is an important arboviral disease. All four dengue virus serotypes are reported to be circulating in India. It is also known that different serotypes, genotypes and clades of genotype determine outbreak severity. Dengue affected children are known to have serious disease outcome. We carried out this study to give reliable diagnosis of dengue infection in children and to detect circulating serotype in central India. Methods: Samples collected from paediatric patients suspected to have dengue fever were subjected to IgM and IgG ELISA to determine dengue virus infection. Samples collected within 0-5 days of onset of illness and positive by IgM ELISA were tested by nested reverse transcription polymerase chain reaction (nRT-PCR). The PCR products were sequenced and analyzed. Results: Of the 89 samples tested, 18 and 7 were positive for dengue IgM and IgG, respectively. Dengue activity was observed in both Jabalpur city and adjoining rural settings. One sample found positive by nRT-PCR was further sequenced to confirm dengue virus 4 as aetiological agent. Interpretation & conclusions: Our findings demonstrated dengue virus infection in children and adolescent in central India. Because of continuous changing epidemiology, it is important to monitor dengue virus activity at both serological and molecular level in this part of the country for better patient care and management.

Sequence determination and phylogenetic tree analysis of the E gene of dengue virus type 4 isolated from a patient in Shenzhen / 中国人兽共患病学报

To identify the genotype and analyze the molecular characteristics of dengue virus strain SZ0524 isolated from serum samples of patients with early stage of dengue fever in Shenzhen in 2005 so as to explore its possible origin. The C6/36 cell line was cultivated with virus strain SZ0524 and its suspension was harvested. The type of isolated virus strain was determined by RT-semi-nested PCR and fluorescent PCR. E gene of isolated virus strain was amplified by RT-PCR and sequenced. Homology and phylogenetic tree of E gene of this dengue virus with the strains isolated from other areas were constructed. This SZ0524 strain was further identified by fluorescent PCR, and confirmed to be the type 4 virus after obtaining the 392bp band with type 4 specific primers. The homology of nucleotide sequence of E gene of SZ0524 strain with the standard type 4 dengue virus H241 strain were 99.7%, but the homology with the standard dengue virus 1,2,3 in the same fragment were 57.0%, 59.2% and 56.2% respectively. Analysis of the phylogenetic tree indicated that SZ0524 was more close to D4-73NIID and D4-61NIID strain, next to H241 strain, and they lied in the same branch of phylogenetic tree. The isolated dengue virus type 4 belonged to genotype Ⅰand the SZ0524 strain was proved to be dengue virus type 4 in the molecular level. Combined with epidemiology information, it is suggested that this case can be classified as an imported case and the SZ0524 strain may be transferred from the southeast asian region.