Epidemiological and molecular characteristics of emergent dengue virus in Yunnan Province near the China-Myanmar-Laos border, 2013–2015

Abstract

BackgroundYunnan Province is located in southwestern China and neighbors the Southeast Asian countries, all of which are dengue-endemic areas. In 2000–2013, sporadic imported cases of dengue fever (DF) were reported almost annually in Yunnan Province. During 2013–2015, we confirmed that a large-scale indigenous DF outbreak emerged in cities of Yunnan Province near the China-Myanmar-Laos border.MethodsEpidemiological characteristics of DF in Yunnan Province during 2013–2015 were evaluated by retrospective analysis. A total of 232 dengue virus (DENV)-positive sera were randomly collected for sequence analysis of the capsid/premembrane region of DENV from patients with DF in Yunnan Province. The envelope gene of DENV isolates was also amplified and sequenced. Phylogenetic analyses were performed using the neighbor-joining method with the Tajima-Nei model.ResultsPhylogenetically, all DENV-positive samples could be classified into DENV-1 genotype I and DENV-2 Asian I genotype during 2013–2015 and DENV-4 genotype I in 2015 from Ruili City; and DENV-3 genotype II in 2013 and DENV-2 Cosmopolitan genotype in 2015 from Xishuangbanna Prefecture.ConclusionsOur results indicated that imported DF from patients from Laos and Myanmar was the primary cause of the DF epidemic in Yunnan Province. Additionally, DENV strains of all four serotypes were identified in indigenous cases in Yunnan Province during the same time period, while the dengue epidemic pattern observed in southwestern Yunnan showed characteristics of a hypoendemic nature: circulation of DENV-1 and DENV-2 over consecutive years.Electronic supplementary materialThe online version of this article (doi:10.1186/s12879-017-2401-1) contains supplementary material, which is available to authorized users.

Molecular characterization of the viral structural gene of the first dengue virus type 1 outbreak in Xishuangbanna, a border area of China, Burma and Laos

“…According to the National Notifiable Disease Surveillance System, from 2002 to 2016, the incidence ranged from 0.01 to 3.46 per 100,000 people with a total of seven deaths reported. In 2014, there were more than 44,000 reported cases of dengue fever, which stands out as the highest-ever number of dengue infections per year in the historical records [15,16]. Yunnan Province is located in southwestern China and neighbors the southeast Asian countries, which are all dengue-endemic areas.…”

“…Yunnan Province is located in southwestern China and neighbors the southeast Asian countries, which are all dengue-endemic areas. Research indicates that imported DF from patients from Laos and Myanmar was the primary cause of the DF epidemic in Yunnan Province [17,18,19], whereas Chinese encouragement of implementing economic development policy with Southeast Asian will result in greater contacts between Yunnan and southeast Asian countries. This finding indicates that the dengue epidemic might become increasingly common in this Chinese border area.…”

“…Previous studies report that the imported cases in China (2013-2016) were mainly from Asian countries, such as Burma and African countries, which also varied with the type of infectious disease [23,24,25]. In addition, epidemiological and molecular characteristics of emergent dengue virus in Yunnan Province (2013-2015) indicated that imported DF from patients of Laos and Myanmar were the primary cause of the DF epidemic in the Yunnan Province [12]. The results of the phylogenetic analysis show that all 97 strains of dengue virus were serotype 1 DENV and can be divided into three clusters in the ML tree.…”

“…Since that outbreak, epidemics have been regularly reported in Yunnan [10]. Xishuangbanna, which is located in the southwestern Yunnan Province and is a border city with China, Burma and Laos, was reported in 2013 to have the first outbreak with 1319 confirmed DENV-3 cases [11,12,13]. Later, 1132 confirmed DENV-2 cases were reported in Xishuangbanna in 2015 [14].…”

Molecular characterization of the viral structural gene of the first dengue virus type 1 outbreak in Xishuangbanna: A border area of China, Burma and Laos

“…Since that outbreak, epidemics have been regularly reported in Yunnan (Du and Pan, 2010). Xishuangbanna, which is located in the southwestern Yunnan Province and is a border city with China, Burma and Laos, was reported in 2013 to have the first outbreak with 1319 confirmed DENV-3 cases (Wang et al, 2017a;Hu et al, 2017a;Wang et al, 2016). Later, 1132 confirmed DENV-2 cases were reported in Xishuangbanna in 2015 (Zhao et al, 2016).…”