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 Aedes aegypti compared to Aedes albopictus 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.
Highlights
In the context of globalization of trade and travel, the arboviruses’ epidemiology profiles have changed and their expansion is in constant progression [1]
This study is a first step in filling this gap by providing genetic and epidemiologic information on the first dengue virus (DENV)-4 epidemic recorded in Lao People’s Democratic Republic (PDR)
The progressive increase of DENV-4 burden occurred in a context of the co-circulation of different DENV serotypes previously described and maintained over the eight years of surveillance (i.e., 2012–2019) [29,30,31]
Summary
In the context of globalization of trade and travel, the arboviruses’ epidemiology profiles have changed and their expansion is in constant progression [1]. Recent World Health Organization (WHO) statistics revealed an increase of the number of dengue cases reported from 505,430 cases in 2000 to 4.2 million in 2019, among which. 70% of the burden is supported by Asia, and a modelling study estimated that 390 million people are infected by dengue virus per year [2,3,4]. Even if these data should be interpreted cautiously, due to changes in declaration systems and the increased number of contributing countries, they do reflect an alarming evolution of dengue virus (DENV) epidemiology. The number of fatal dengue cases has increased from 960 in 2000 to 4032 in 2015 [4]
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