title: Dengue virus in sub-tropical northern and central Viet Nam: population immunity and climate shape patterns of viral invasion and maintenance.
abstract: Dengue virus transmission occurs in both epidemic and endemic cycles across tropical and sub-tropical regions of the world. Incidence is particularly high in much of Southeast Asia, where hyperendemic transmission plagues both urban and rural populations. However, endemicity has not been established in some areas with climates that may not support year-round viral transmission. An understanding of how dengue viruses (DENV) enter these environments and whether the viruses persist in inapparent local transmission cycles is central to understanding how dengue emerges in areas at the margins of endemic transmission. Dengue is highly endemic in tropical southern Vietnam, while increasingly large seasonal epidemics have occurred in northern Viet Nam over the last decade. We have investigated the spread of DENV-1 throughout Vietnam to determine the routes by which the virus enters northern and central regions of the country. Phylogeographic analysis of 1,765 envelope (E) gene sequences from Southeast Asia revealed frequent movement of DENV between neighboring human populations and strong local clustering of viral lineages. Long-distance migration of DENV between human population centers also occurred regularly and on short time-scales, indicating human-mediated viral invasion into northern Vietnam. Human populations in southern Vietnam were found to be the primary source of DENV circulating throughout the country, while central and northern Vietnam acted as sink populations, likely due to reduced connectedness to other populations in the case of the central regions and to the influence of temperature variability on DENV replication and vector survival and competence in the north. Finally, phylogeographic analyses suggested that viral movement follows a gravity model and indicates that population immunity and physical and economic connections between populations may play important roles in shaping patterns of DENV transmission.
authors: Centre for Immunity, Infection and Evolution, University of Edinburgh, Edinburgh, United Kingdom ; Oxford University Clinical Research Unit, Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam.
authors: Maia A
authors: MA
authors: Rabaa
authors: Cameron P
authors: CP
authors: Simmons
authors: Annette
authors: A
authors: Fox
authors: Mai Quynh
authors: MQ
authors: Le
authors: Thuy Thi Thu
authors: TT
authors: Nguyen
authors: Hai Yen
authors: HY
authors: Le
authors: Robert V
authors: RV
authors: Gibbons
authors: Xuyen Thanh
authors: XT
authors: Nguyen
authors: Edward C
authors: EC
authors: Holmes
authors: John G
authors: JG
authors: Aaskov
mesh_terms: D002980:Climate; D016000:Cluster Analysis; D003715:Dengue / Q000453:epidemiology* / Q000276:immunology*; D003716:Dengue Virus / Q000145:classification / Q000235:genetics / Q000276:immunology* / Q000302:isolation & purification; D006801:Humans; D017720:Molecular Epidemiology; D008969:Molecular Sequence Data; D058974:Phylogeography; D017422:Sequence Analysis, DNA; D017385:Sequence Homology; D014744:Vietnam / Q000453:epidemiology; D014759:Viral Envelope Proteins / Q000235:genetics
chemical_list: D014759:Viral Envelope Proteins; C072281:E protein TH Sman, Dengue virus