Abstract
BackgroundDengue hemorrhagic fever is an acute viral infection transmitted by mosquitoes. In the 2017, a dengue epidemic occurred in Hanoi in a short time interval and many cases were serious with associated mortality. This was the largest and unusual dengue fever outbreak in the North of Vietnam over the past 20 years. The objective of the present study was to understand the genetic characteristics of the DENV-1 strain in the 2017 epidemic and its relationship with previous viruses in Vietnam and the rest of the world.MethodsComplete genomes of 72 DENV-1 from patients in the 2017 epidemic were sequenced using NGS. The full genome sequences were then analyzed to find out the genetic variants in the groups of 72 strains, followed by their comparison with other strains that caused disease in Vietnam previously and several other regions of the world, revealing a genetic relationship between them.ResultsThe complete genome sequence of 72 DENV-1 strains comprised 10,697 nucleotides with an open reading frame coding for 3392 amino acids. The genomic analysis revealed different amino acid substitutions in all genes, especially varying at position S75 (Capsid), M125 (PrM), D54 (E), T147, V180 (NS1), G45, Y126, I154 (NS2A), A94 (NS2B), M298 (NS3), K47, V68 (NS4A), I29 (NS4B), and R166, E536, G614, T821 (NS5). The genetic analysis suggested that the viruses were most closely related to the causative virus of the dengue outbreak in Vietnam and Cambodia from 2006 to 2008. These results indicated that DENV-1 from the dengue epidemic 2017 in Northern Vietnam originated from the virus that caused the dengue outbreak during the 2007 to 2008 period in Vietnam.ConclusionThe present study is the first of its kind to describe complete genome sequence as well as genetic variants and phylogenetic analysis of DENV-1 associated with the unusual dengue epidemic of 2017 in northern Vietnam. These results provide detailed evidence to elucidate the origin, circulation, and genetic evolution of DENV in Vietnam.
Highlights
Dengue hemorrhagic fever is an acute viral infection transmitted by mosquitoes
Dengue hemorrhagic fever can result in major epidemics; these often occur in the Asia and Western Pacific countries such as India, Malaysia, Singapore, Thailand, and Vietnam with a disease cycle of 3 to 5 years [3, 4]
The Real-time Reverse Transcription PCR (RT-PCR) results from 300 NS-1 positive dengue patients showed 276 samples to be positive for dengue viruses (DENV)–1, 22 samples for DENV–2, one sample for DENV–3, and one sample for DENV–4, there were no co-infections detected (Table 2)
Summary
Dengue hemorrhagic fever is an acute viral infection transmitted by mosquitoes. In the 2017, a dengue epidemic occurred in Hanoi in a short time interval and many cases were serious with associated mortality. This was the largest and unusual dengue fever outbreak in the North of Vietnam over the past 20 years. Dengue hemorrhagic fever is a mosquito-borne acute infection caused by one of four dengue viruses (DENV), the disease mainly spread in tropical and subtropical countries. Dengue hemorrhagic fever can result in major epidemics; these often occur in the Asia and Western Pacific countries such as India, Malaysia, Singapore, Thailand, and Vietnam with a disease cycle of 3 to 5 years [3, 4]. There are four commonly circulating dengue viruses in the world, which share a similarity of 65 to 70% of amino acid sequences [8]
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