![]() ![]() Dengue fever is characterized by a sudden onset of high-grade fever with non-specific symptoms and most cases resolve without specific treatment. Dengue infections may be asymptomatic or symptomatic, classified as dengue fever (DF), dengue haemorrhagic fever (DHF), and dengue shock syndrome (DSS) or more recently as dengue, dengue with warning signs and severe dengue. WHO estimates that 50–100 million people are infected by dengue globally every year. More investigations are needed to understand the relationships between dengue in forested and urban areas.ĭengue is endemic in more than 100 countries in Asia, Africa and the Americas, but 70% of those currently at risk live in South-East Asia and the Western Pacific. The dengue virus isolated from patients in the forest village outbreak proved to be genetically similar to those found in urbanized areas throughout the country. Results suggest three patterns of dengue circulation in Laos: local transmission, transmission over the whole country, and transmission implicating bordering countries. It also is the first extensive analysis of dengue virus nucleotide sequences, from 39 patients across the country, from Laos. This study reports an unusual outbreak of dengue that occurred during the cold season in a village in a forested area. ![]() In the Lao PDR, a developing country where dengue is endemic, data on this disease are sparse. Most common is the human-mosquito-human cycle observed throughout most tropical regions of the world, often associated with urban locations and always human habitations, often producing explosive outbreaks, whereas “sylvatic” dengue, genetically different, circulates in forest wild animals and has been reported to be able to infect humans. Two distinct transmission cycles have been described. Major outbreaks, including severe cases and death, occur every year. In Southeast Asia, where it is endemic, it represents a very important public health problem. Groups of sequences supported by a high bootstrap value (91 for cluster 1, 100 for cluster 2, 3 and 4, 97 for cluster 5, 84 for cluster 6, 97 for cluster 7) that contain at least one of Lao sequence are designated as cluster (1 to 7).ĭengue disease is caused by a virus transmitted by mosquitoes. For the other sequences only the country, using ISO3166 code, and the year of origin are indicated. Sequences from 2007 are in yellow, the ones from 2008 (except those from Latsavang) are in purple, the ones from 2009 in blue and the ones from 2010 in green. Sequences from Luang Namtha (LNT) are indicated by squares, the ones from Salavan (SV) by triangles and those from Vientiane (VTE) by lozenges. Sequences from the Latsavang outbreak are indicated by red dots. Given the high number of sequences displayed in this subtree, origin and date are indicated for group of sequences. Evolutionary branches that do not include 2007–2010 Lao DENV-1 strains are not shown in order to increase the legibility. Genotype 1 subtree, 1,627 sequences, from the Maximum Likelihood tree in Figure S2, produced with 2,199 dengue 1 envelope gene sequences. Groups of sequences supported by a high bootstrap value (>90) that contain at least one of Lao sequence are designated as cluster (1 to 7).įigure S3: Genotype 1 subtree with envelope sequences. ![]() ![]() Genotype 1 subtree, 1,627 sequences, from the Neighbour-Joining tree in Figure 2, produced with 2,199 dengue 1 envelope gene sequences. Figure S1: Genotype 1 subtree with envelope sequences. ![]()
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