Rapid genotyping protocol to improve dengue virus serotype 2 survey in Lao PDR

Abstract

Dengue fever is one of the major public health problems in Lao PDR. Over the last decade, dengue virus (DENV) epidemics were characterized by a novel predominant serotype accompanied by at least two other serotypes. Since 2008, DENV-2 circulated at a low level in Lao PDR but its epidemiologic profile changed at the end of 2018. Indeed, the number of confirmed DENV-2 cases suddenly increased in October 2018 and DENV-2 became predominant at the country level in early 2019. We developed a Genotype Screening Protocol (GSP) to determine the origin(s) of the Lao DENV-2 and study their genetic polymorphism. With a good correlation with full envelope gene sequencing data, this molecular epidemiology tool evidence the co-circulation of two highly polymorphic DENV-2 genotypes, i.e. Asian I and Cosmopolitan genotypes, over the last five years, suggesting multiple introductions of DENV-2 in the country. GSP approach provides relevant first line information that may help countries with limited laboratory resources to reinforce their capabilities to DENV-2 and to follow the epidemics progresses and assess situations at the regional level.

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

“…Subsequently, the proportion of DENV-4 cases gradually increased among the samples tested by the arbovirus surveillance network in Vientiane Capital and became predominant in 2016 at the country level until October 2018. Since then, DENV-2 has overcome DENV-4 in Vientiane Capital and at the country level [33]. However, DENV-4 still circulated at a significant level in 2019 (13%; Figure 2).…”

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

“…For instance, in 2006, in Vientiane Capital 84.6% of the adults above 35 years (N = 1990) displayed IgG reactive to DENV antigen but only 9.4% of the children (≥6 months and <6 years; N = 1568) were found to be positive [26]. Since 2012, three major outbreaks have occurred in the Lao PDR predominated by DENV-3 (2012-13), DENV-4 (2016-18) and DENV-2 (2019-20) [17][18][19]. Even if DENV-1 was detected before 2010, among the samples tested in the Lao PDR [13,15,16], its circulation over the last 10 years was not actually very widespread in a national context.…”

“…Blood samples (5 mL of venous blood) were collected by clinicians from the arbovirus surveillance hospital network in Vientiane Capital and some of the Lao provinces [17][18][19]. Briefly, suspected patients, presenting dengue fever symptoms matching with the WHO's case definition (fever onset ≥38 • C for less than 7 days with at least one of the following accompanying symptoms: headache, myalgia, arthralgia, retro-orbital pain, digestive troubles or hemorrhaging), were included in this study after obtaining informed consent.…”

“…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.…”