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

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.

SUBMITTER: Calvez E

PROVIDER: S-EPMC8617722 | biostudies-literature | 2021 Oct

REPOSITORIES: biostudies-literature

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

Calvez Elodie E Bounmany Phaithong P Balière Charlotte C Somlor Somphavanh S Viengphouthong Souksakhone S Xaybounsou Thonglakhone T Keosenhom Sitsana S Fangkham Kitphithak K Brey Paul T PT Caro Valérie V Lacoste Vincent V Grandadam Marc M

Microorganisms 20211030 11

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 ...[more]

PMID: 34835389

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Project description:BackgroundDuring the 2013 outbreak, 4638 infection cases and 32 deaths have been recorded in the southern part of Laos. In recent years, the chikungunya virus (CHIKV) emerged in the part of the country bordering Cambodia. Dengue virus (DENV) and CHIKV are transmitted by common mosquito vectors. Both diseases have similar clinical presentations; therefore, CHIKV infections might go undiagnosed in DENV-endemic areas. Thus, rapid detection and accurate diagnosis are crucial for differentiating between the two viruses (DENV and CHIKV). In this study, we demonstrated that CHIKV and two serotypes of DENV are circulating in Laos. In addition, we encountered patients that had been concurrently infected with multiple DENV serotypes or DENV and CHIKV.MethodsPlasma samples were collected from 40 patients with suspected DENV infections during an outbreak between July and August 2013. The reverse transcription polymerase chain reaction was performed to detect the four DENV serotypes and CHIKV using specific primers. Specifically, the complete envelope gene sequences of the viruses were sequenced and subjected to phylogenetic analysis.ResultsForty acute-phase plasma samples from patients with suspected dengue infections were tested for the presence of DENV viral RNA using molecular methods. Among the 40 samples, 14 samples were positive for DENV, 2 samples were positive for both viruses (DENV-2 and DENV-3), whereas DENV-1 and DENV-4 were not detected during the study period. We also encountered 10 samples that were positive for CHIKV. Of the 10 CHIKV-positive samples, 3 samples were co-infected by DENV-2, and 2 samples were co-infected by DENV-3. Phylogenetic analysis revealed that the 2013 dengue outbreak in Laos involved DENV-2 genotype Asian I and DENV-3 genotype II. Moreover, the Laotian CHIKV strains grouped together with those isolated during outbreaks on the Indian Ocean Islands within the East Central South African genotype.ConclusionsThese findings revealed that two serotypes (DENV-2 and DENV-3) and CHIKV were detected. Furthermore, infection of multiple DENV serotypes and CHIKV was also observed in the 2013 dengue outbreak. This is the first documented evidence of co-infection with CHIKV and one of two DENV serotypes.

Project description:BackgroundIn the Greater Mekong Subregion (GMS), forest-going populations are considered high-risk populations for malaria and are increasingly targeted by national control programmes' elimination efforts. A better understanding of forest-going populations' mobility patterns and risk associated with specific types of forest-going trips is necessary for countries in the GMS to achieve their objective of eliminating malaria by 2030.MethodsBetween March and November 2018, as part of a focal test and treat intervention (FTAT), 2,904 forest-goers were recruited in southern Lao PDR. A subset of forest-goers carried an "i-Got-U" GPS logger for roughly 2 months, configured to collect GPS coordinates every 15 to 30 min. The utilization distribution (UD) surface around each GPS trajectory was used to extract trips to the forest and forest-fringes. Trips with shared mobility characteristics in terms of duration, timing and forest penetration were identified by a hierarchical clustering algorithm. Then, clusters of trips with increased exposure to dominant malaria vectors in the region were further classified as high-risk. Finally, gradient boosting trees were used to assess which of the forest-goers' socio-demographic and behavioural characteristics best predicted their likelihood to engage in such high-risk trips.ResultsA total of 122 forest-goers accepted carrying a GPS logger resulting in the collection of 803 trips to the forest or forest-fringes. Six clusters of trips emerged, helping to classify 385 (48%) trips with increased exposure to malaria vectors based on high forest penetration and whether the trip happened overnight. Age, outdoor sleeping structures and number of children were the best predictors of forest-goers' probability of engaging in high-risk trips. The probability of engaging in high-risk trips was high (~ 33%) in all strata of the forest-going population.ConclusionThis study characterized the heterogeneity within the mobility patterns of forest-goers and attempted to further segment their role in malaria transmission in southern Lao People's Democratic Republic (PDR). National control programmes across the region can leverage these results to tailor their interventions and messaging to high-risk populations and accelerate malaria elimination.

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

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

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