Trends of the Dengue Serotype-4 Circulation with Epidemiological, Phylogenetic, and Entomological Insights in Lao PDR between 2015 and 2019

Abstract

Dengue outbreaks have regularly been recorded in Lao People’s Democratic Republic (PDR) since the first detection of the disease in 1979. In 2012, an integrated arbovirus surveillance network was set up in Lao PDR and an entomological surveillance has been implemented since 2016 in Vientiane Capital. Here, we report a study combining epidemiological, phylogenetic, and entomological analyzes during the largest DENV-4 epidemic ever recorded in Lao PDR (2015–2019). Strikingly, from 2015 to 2019, we reported the DENV-4 emergence and spread at the country level after two large epidemics predominated by DENV-3 and DENV-1, respectively, in 2012–2013 and 2015. Our data revealed a significant difference in the median age of the patient infected by DENV-4 compared to the other serotypes. Phylogenetic analysis demonstrated the circulation of DENV-4 Genotype I at the country level since at least 2013. The entomological surveillance showed a predominance of Aedesaegypti compared to Aedesalbopictus and high abundance of these vectors in dry and rainy seasons between 2016 and 2019, in Vientiane Capital. Overall, these results emphasized the importance of an integrated approach to evaluate factors, which could impact the circulation and the epidemiological profile of dengue viruses, especially in endemic countries like Lao PDR.

Genetic Diversity of Dengue Virus in Clinical Specimens from Bangkok, Thailand, during 2018–2020: Co-Circulation of All Four Serotypes with Multiple Genotypes and/or Clades

“…In contrast, PW-34, TM20-05, and TM20-59 were in clade b (DENV-4-Ib) and related to sequences from Thailand and Attapeu Province, Laos [30,32,66], collected on dates similar to our sequences collected in 2018-2019. Viruses isolated in Thailand in 2011-2012 (MW94550 and MW945637) were the ancestral strains of this clade.…”

“…The phylogenetic tree suggested that Thailand is the center of DENV-4 distribution in Southeast Asia. Although genotype I emerged and spread through in Laos [ 66 ], these sequences originated from Thailand viruses showing a specific distribution in this area [ 81 , 82 ]. Moreover, DENV-4 dominated for only a short period in Thailand during 1993–1994 perhaps due to immunological cross-reaction between DENV-4 and the other serotypes in the population [ 66 ].…”

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

“…Then, an outbreak of DENV-3 was reported in 2012-2013 [17]. While recent studies on DENV-4 and DENV-2 have demonstrated the low level of circulation of these two serotypes before 2014, major outbreaks were subsequently reported in 2016-2018 (DENV-4) and 2019-2020 (DENV-2), during which changes in genotypes and/or clusters within these serotypes could be observed [18,19]. In the meantime, DENV-1 continuously circulated, representing between 16% and 22% of the serotyped samples at the national level yearly [13,[15][16][17][18][19].…”

“…While recent studies on DENV-4 and DENV-2 have demonstrated the low level of circulation of these two serotypes before 2014, major outbreaks were subsequently reported in 2016-2018 (DENV-4) and 2019-2020 (DENV-2), during which changes in genotypes and/or clusters within these serotypes could be observed [18,19]. In the meantime, DENV-1 continuously circulated, representing between 16% and 22% of the serotyped samples at the national level yearly [13,[15][16][17][18][19]. Therefore, in the context of co-circulation of different DENV serotypes, we aimed to better characterize the circulation of DENV-1 in the Lao PDR between 2016 and 2020 through epidemiological and phylogenetic investigations.…”

On‐Chip Optical Detection of Viruses: A Review

“…[ 3–7 ] In tropical countries such as Singapore, the mosquito breeding also leads to the spread of dengue disease, leading to 4.2 million cases worldwide in 2019. [ 8 ]…”