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.
Highlights
Yunnan Province is located in southwestern China and neighbors the Southeast Asian countries, all of which are dengue-endemic areas
In 2015, a re-emerging, large-scale indigenous dengue fever (DF) outbreak was reported in Xishuangbanna, which was triggered by imported cases from Laos and Myanmar
The present study suggested that multiple dengue virus (DENV) serotypes are endemic in countries bordering Yunnan Province such as Laos, Thailand, and Myanmar
Summary
Yunnan 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. Complex factors, including climate change, poor vector control, virus evolution, increased population mobility, uncontrolled urbanization, and the lack of effective vaccines, have aggravated the incidence and geographic expansion of dengue [6,7,8]. Epidemic dengue outbreaks have been reported in Asia and almost all countries in Southeast Asia, including Laos, Myanmar, Indonesia, Cambodia, Malaysia, Philippines, Thailand, and Vietnam [9,10,11,12,13,14,15,16,17,18]. DENV strains of all four serotypes have been identified in southeastern China
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