Using Background Sequencing Data to Anticipate DENV-1 Circulation in the Lao PDR.

Elodie Calvez,Charlotte Balière,Marc Grandadam,Somphavanh Somlor,Kitphithak Fangkham,Paul T Brey,Phaithong Bounmany,Vincent Lacoste,Valérie Caro,Souksakhone Viengphouthong,Thonglakhone Xaybounsou,Sitsana Keosenhom

doi:10.3390/microorganisms9112263

Abstract

Since its first detection in 1979, dengue fever has been considered a major public health issue in the Lao People’s Democratic Republic (PDR). Dengue virus (DENV) serotype 1 was the cause of an epidemic in 2010–2011. Between 2012 and 2020, major outbreaks due successively to DENV-3, DENV-4 and recently DENV-2 have been recorded. However, DENV-1 still co-circulated in the country over this period. Here, we summarize epidemiological and molecular data of DENV-1 between 2016 and 2020 in the Lao PDR. Our data highlight the continuous circulation of DENV-1 in the country at levels ranging from 16% to 22% among serotyping tests. In addition, the phylogenetic analysis has revealed the circulation of DENV-1 genotype I at least since 2008 with a co-circulation of different clusters. Sequence data support independent DENV-1 introductions in the Lao PDR correlated with an active circulation of this serotype at the regional level in Southeast Asia. The maintenance of DENV-1 circulation over the last ten years supports a low level of immunity against this serotype within the Lao population. Thereby, the risk of a DENV-1 epidemic cannot be ruled out in the future, and this emphasizes the importance of maintaining an integrated surveillance approach to prevent major outbreaks.

Highlights

Dengue viruses (DENVs) are the most prevalent human arboviruses worldwide as a direct consequence of the distribution of the main dengue viruses’ vector Aedes species (Aedes aegypti, Aedes albopictus) [1]
Epidemiological studies in the Lao People’s Democratic Republic (PDR) revealed a cascade of epidemics due to a rapid switch in the predominance of DENV serotypes (Figure 1)
A successive predominance of DENV-3, DENV-4 and DENV-2 was observed in the Lao PDR, as previously described [18]

Summary

Introduction

Dengue viruses (DENVs) are the most prevalent human arboviruses worldwide as a direct consequence of the distribution of the main dengue viruses’ vector Aedes species (Aedes aegypti, Aedes albopictus) [1]. In 2019, 4.2 million dengue cases were reported by the. World Health Organization (WHO), with 70% of the burden in Asia. The global surge in dengue between 2000 and 2015 was accompanied by more than a 4-fold increase in the number of reported deaths [2]. DENV are positive-sense RNA viruses (Flavivirus genus; Flaviviridae family) of which four distinct serotypes were identified (DENV-1 to DENV-4) [3,4,5,6]. DENV-1 was first detected in 1943 in French Polynesia and Japan and seemed to be the most reported serotype between 1943 and 2013 [7,8]. Five DENV-1 genotypes are currently described: genotype I (Asia), II (Thailand), III (Malaysia), IV (South Pacific) and V (America/Africa) [10,11]

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