Context Dengue virus (DENV) causes acute febrile illness in tropical and subtropical countries. In India there is a steady increase in incidence since 1950s which could be attributed to emergence of new serotype or lineage\clade shifts in circulating DENV. Aims We aimed to perform molecular characterisation and phylogenetic analysis on samples from the recent outbreak (August-October 2017). Settings and Design Retrospective epidemiological analysis of dengue outbreak. Subjects and Methods Samples positive for non-steroidal 1 antigen by enzyme-linked immunosorbent assay (n = 147) were included. The study was approved by our institute ethics committee (JIP/IEC/2018/496). Five hundred and eleven base pair of capsid and pre-membrane encoding genes (CprM) region was amplified using Lanciotti primers, followed by second round of polymerase chain reaction using serotype specific primers. Samples which were positive by second round (n = 68) were sequenced and genotyped using Basic Local Alignment Search Tool analysis and phylogenetic tree was constructed by MEGA7 software. Results Phylogenetic analysis of CprM sequences identified all 4 serotypes in circulation during this outbreak. We observed both single (n = 50) and concurrent infections (n = 18), with DENV4 as the major contributor (64%). Within Genotype I of DENV4 we observed a distinct new clade (Clade E) which was 2.6% ± 0.9%-5.5% ± 1.1% divergent from the other clades. Among the concurrent infection, DENV 4 and DENV 2 combination was observed to form the majority (77.8%). Conclusions Overall this study documents the emergence of DENV4 as the major serotype in circulation, replacing DENV1, 2 and 3 which had been previously reported from Tamil Nadu and Puducherry. This substantiates the need for continuous monitoring in endemic countries like India, where such data may impact the formulation of vaccine policy for dengue.

中文翻译：

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2017 年印度南部爆发期间，登革热病毒 4 型成为主要血清型。

背景 登革热病毒 (DENV) 在热带和亚热带国家引起急性发热性疾病。在印度，自 20 世纪 50 年代以来，发病率稳步上升，这可能是由于流行的 DENV 出现新血清型或谱系\进化枝变化所致。目标 我们的目标是对最近爆发（2017 年 8 月至 10 月）的样本进行分子表征和系统发育分析。设置和设计登革热暴发的回顾性流行病学分析。受试者和方法 酶联免疫吸附测定显示非甾体 1 抗原呈阳性的样本 (n = 147) 被纳入其中。该研究得到了我们研究所伦理委员会的批准（JIP/IEC/2018/496）。使用 Lanciotti 引物扩增衣壳和前膜编码基因 (CprM) 区域的 511 个碱基对，然后使用血清型特异性引物进行第二轮聚合酶链式反应。使用基本局部比对搜索工具分析对第二轮阳性的样本（n = 68）进行测序和基因分型，并通过 MEGA7 软件构建系统发育树。结果 CprM 序列的系统发育分析鉴定出了本次疫情期间流行的所有 4 种血清型。我们观察到单一感染 (n = 50) 和并发感染 (n = 18)，其中 DENV4 是主要贡献者 (64%)。在 DENV4 的基因型 I 中，我们观察到一个独特的新进化枝（进化枝 E），其与其他进化枝的差异为 2.6% ± 0.9%-5.5% ± 1.1%。在并发感染中，DENV 4和DENV 2组合占大多数（77.8%）。结论 总体而言，本研究记录了 DENV4 成为流行的主要血清型，取代了先前在泰米尔纳德邦和本地治里报道的 DENV1、2 和 3。这证实了在印度等流行国家进行持续监测的必要性，这些数据可能会影响登革热疫苗政策的制定。