Molecular epidemiology suggests Venezuela as the origin of the dengue outbreak in Madeira, Portugal in 2012-2013

Winged Threat on the Offensive: A Literature Review Due to the First Identification of Aedes japonicus in Poland

Genetic studies preceded by the observation of an unknown mosquito species in Mikołów (Poland) confirmed that it belongs to a new invasive species in Polish fauna, Aedes japonicus (Theobald, 1901), a known vector for numerous infectious diseases. Ae. japonicus is expanding its geographical presence, raising concerns about potential disease transmission given its vector competence for chikungunya virus, dengue virus, West Nile virus, and Zika virus. This first genetically confirmed identification of Ae. japonicus in Poland initiates a comprehensive review of the literature on Ae. japonicus, its biology and ecology, and the viral infections transmitted by this species. This paper also presents the circumstances of the observation of Ae. japonicus in Poland and a methodology for identifying this species.

Flying under the radar - impact and factors influencing asymptomatic DENV infections

The clinical outcome of DENV and other Flaviviruses infections represents a spectrum of severity that ranges from mild manifestations to severe disease, which can ultimately lead to death. Nonetheless, most of these infections result in an asymptomatic outcome that may play an important role in the persistent circulation of these viruses. Also, although little is known about the mechanisms that lead to these asymptomatic infections, they are likely the result of a complex interplay between viral and host factors. Specific characteristics of the infecting viral strain, such as its replicating efficiency, coupled with host factors, like gene expression of key molecules involved in the immune response or in the protection against disease, are among crucial factors to study. This review revisits recent data on factors that may contribute to the asymptomatic outcome of the world's widespread DENV, highlighting the importance of silent infections in the transmission of this pathogen and the immune status of the host.

HIV Surveillance and Research for Migrant Populations: Protocol Integrating Respondent-Driven Sampling, Case Finding, and Medicolegal Services for Venezuelans Living in Colombia

BACKGROUND

Epidemiologic research among migrant populations is limited by logistical, methodological, and ethical challenges, but it is necessary for informing public health and humanitarian programming.

OBJECTIVE

We describe a methodology to estimate HIV prevalence among Venezuelan migrants in Colombia.

METHODS

Respondent-driven sampling, a nonprobability sampling method, was selected for attributes of reaching highly networked populations without sampling frames and analytic methods that permit estimation of population parameters. Respondent-driven sampling was modified to permit electronic referral of peers via SMS text messaging and WhatsApp. Participants complete sociobehavioral surveys and rapid HIV and syphilis screening tests with confirmatory testing. HIV treatment is not available for migrants who have entered Colombia through irregular pathways; thus, medicolegal services integrated into posttest counseling provide staff lawyers and legal assistance to participants diagnosed with HIV or syphilis for sustained access to treatment through the national health system. Case finding is integrated into respondent-driven sampling to allow partner referral. This study is implemented by a local community-based organization providing HIV support services and related legal services for Venezuelans in Colombia.

RESULTS

Data collection was launched in 4 cities in July and August 2021. As of November 2021, 3105 of the target 6100 participants were enrolled, with enrollment expected to end by February/March 2022.

CONCLUSIONS

Tailored methods that combine community-led efforts with innovations in sampling and linkage to care can aid in advancing health research for migrant and displaced populations. Worldwide trends in displacement and migration underscore the value of improved methods for translation to humanitarian and public health programming.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/36026.

Global dengue importation: a systematic review

Background

Importation of dengue following globalization presents an emerging threat to global health. However, evidence on global geographical sources and the potential of dengue importation globally are lacking. This study aims to systematically review the sources of dengue importation globally and the risk of dengue outbreaks globally.

Methods

This systematic review was conducted in accordance to Cochrane’s PRISMA guidelines. Articles published through 31 December 2019 with laboratory-confirmed dengue imported cases were consolidated from PubMed, EMBASE and Scopus. Sources of dengue importation reported worldwide were analysed by country and geographical regions. Sources of dengue importation into United States of America and Europe specifically were also analysed.

Results

A total of 3762 articles were found. Among which, 210 articles—documenting 14,972 imported dengue cases with reported sources—were eligible. 76.3% of imported cases worldwide were from Asia. 15.7%, 5.6%, 2.0% and 0.1% were imported from the Americas, Africa, Oceania and Europe regions respectively. Imported dengue cases in the U.S. were from Americas (55.3%), Asia (34.7%), Africa (6.7%) and Oceania (3.3%). Imported dengue cases in Europe were from Asia (66.0%), Americas (21.9%), Africa (10.8%) and Oceania (1.1%).

Conclusion

The potential of dengue outbreaks occurring globally, especially among non-endemic regions with dengue-susceptible populations is high. With the expansion of Aedes mosquito population globally due to global warming and globalisation, dengue importation constitutes an emerging global health security threat.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-06740-1.

Molecular Characterization of Imported and Autochthonous Dengue in Northeastern Spain

Dengue is the most significant arbovirus worldwide and a public health threat to non-endemic areas in which Aedes vectors are present. Autochthonous dengue transmission has been reported in several European countries in the last decade. Infected travelers from endemic regions arriving to areas colonized by Aedes albopictus in Europe need to be monitored in surveillance and control programs. We aimed to perform molecular characterization of RT-PCR-positive dengue cases detected in Catalonia, northeastern Spain, from 2013 to 2018. The basic demographic information and the geographical regions of importation were also analyzed. One-hundred four dengue cases were studied (103 imported infections and the first autochthonous case in our region). The dengue virus strains detected were serotyped and genotyped using molecular methods, and phylogenetic analyses were conducted. All four dengue serotypes were detected in travelers, including up to 10 different genotypes, reflecting the global circulation of dengue in endemic areas. The primary travel-related case of the 2018 autochthonous transmission was not identified, but the molecular analysis revealed dengue serotype 1, genotype I of Asian origin. Our results highlight the diversity of imported dengue virus strains and the role of molecular epidemiology in supporting arbovirus surveillance programs.

Diversity of West Nile and Usutu virus strains in mosquitoes at an international airport in Austria

Increased globalization and international transportation have resulted in the inadvertent introduction of exotic mosquitoes and new mosquito‐borne diseases. International airports are among the possible points of entry for mosquitoes and their pathogens. We established a mosquito and mosquito‐borne diseases monitoring programme at the largest international airport in Austria and report the results for the first two years, 2018 and 2019. This included weekly monitoring and sampling of adult mosquitoes, and screening them for the presence of viral nucleic acids by standard molecular diagnostic techniques. Additionally, we surveyed the avian community at the airport, as birds are potentially amplifying hosts. In 2018, West Nile virus (WNV) was detected in 14 pools and Usutu virus (USUV) was detected in another 14 pools of mosquitoes (minimum infection rate [MIR] of 6.8 for each virus). Of these 28 pools, 26 consisted of female Culex pipiens/torrentium, and two contained male Culex sp. mosquitoes. Cx. pipiens/torrentium mosquitoes were the most frequently captured mosquito species at the airport. The detected WNV strains belonged to five sub‐clusters within the sub‐lineage 2d‐1, and all detected USUV strains were grouped to at least seven sub‐clusters among the cluster Europe 2; all strains were previously shown to be endemic in Austria. In 2019, all mosquito pools were negative for any viral nucleic acids tested. Our study suggests that airports may serve as foci of arbovirus activity, particularly during epidemic years, and should be considered when designing mosquito control and arbovirus monitoring programmes.

Phylogenetic and evolutionary analysis of dengue virus serotypes circulating at the Colombian-Venezuelan border during 2015-2016 and 2018-2019

Dengue is an endemic disease in Colombia. Norte de Santander is a region on the border of Colombia and Venezuela and has reported the co-circulation and simultaneous co-infection of different serotypes of the dengue virus (DENV). This study aimed to conduct a phylogenetic analysis on the origin and genetic diversity of DENV strains circulating in this bordering region. Serum samples were collected from patients who were clinically diagnosed with febrile syndrome associated with dengue during two periods. These samples were tested for DENV and serotyping was performed using reverse transcriptase-polymerase chain reaction. Subsequently, positive samples were amplified and the envelope protein gene of DENV was sequenced. Phylogenetic and phylogeographic analyses were performed using the sequences obtained. Basic local alignment search tool analysis confirmed that six and eight sequences belonged to DENV-1 and DENV-2, respectively. The phylogenetic analysis of DENV-1 showed that the sequences belonged to genotype V and clade I; they formed two groups: in the first group, two sequences showed a close phylogenetic relationship with strains from Ecuador and Panama, whereas the other four sequences were grouped with strains from Venezuela and Colombia. In the case of DENV-2, the analysis revealed that the sequences belonged to the Asian–American genotype and clade III. Furthermore, they formed two groups; in the first group, three sequences were grouped with strains from Colombia and Venezuela, whereas the other five were grouped with strains from Venezuela, Colombia and Honduras. This phylogenetic analysis suggests that the geographical proximity between Colombia and Venezuela is favourable for the export and import of different strains among serotypes or clades of the same DENV serotype, which could favour the spread of new outbreaks caused by new strains or genetic variants of this arbovirus. Therefore, this information highlights the importance of monitoring the transmission of DENV at border regions.

Advanced Lyophilised Loop Mediated Isothermal Amplification (L-LAMP) based point of care technique for the detection of dengue virus

Dengue virus infects millions of the people globally each year and its diagnosis remains a challenge. Conventionally used diagnostic methods are complex and time consuming. LAMP technique is a potential alternative for diagnosis of dengue virus. The benefits of LAMP are its ease and ability, as it does not require an expensive equipment and results are effortlessly visualized by the naked eye. However, it does not aid as point of care technique owing to need of contamination free area, deep freezer for chemical storage and primer self amplification. Each small modification in LAMP method bring it towards an ideal point of care technique. An advanced lyophilized loop mediated isothermal amplification (L-LAMP) was developed in which the dye was dried on the cap and reaction reagents was lyophilized at the bottom of the tube to overcome the common hurdles of LAMP technique. The technique was able to diagnose disease within 35 min with 4U of Bst polymerase. The least concentration of dye required was 1000×. Result given by the seminested reverse transcriptase polymerase chain reaction (RT-PCR) and L-LAMP with enzyme linked immuno sorbent assay (ELISA) were compared using Chi square test. The L-LAMP showed 100 % specificity and 92 % sensitivity with respect ELISA and was found better than RT-PCR which showed 100 % specificity and 88 % sensitivity. There was no cross reactivity of primers with other disease like malaria caused by Plasmodium falciparum and P. vivax and with viral disease chikungunya. L-LAMP has dynamic potential as point of care technique.

Health crisis in Venezuela: Status of communicable diseases and implications for the European Union and European Economic Area, May 2019

Re-emerging diseases outbreaks are being reported in Venezuela since 2012/13, following ongoing political and economic crisis. Healthcare system collapse has led to an increasing incidence and mortality from communicable diseases. Increasing movement of people between Venezuela and the European Union and European Economic Area (EU/EEA) creates a need for increased awareness of the infectious disease risks and requirements for appropriate investigation and treatment of individuals arriving from Venezuela; overall risk for EU/EEA citizens is low.

The origins of dengue and chikungunya viruses in Ecuador following increased migration from Venezuela and Colombia

BACKGROUND

In recent years, Ecuador and other South American countries have experienced an increase in arboviral diseases. A rise in dengue infections was followed by introductions of chikungunya and Zika, two viruses never before seen in many of these areas. Furthermore, the latest socioeconomic and political instability in Venezuela and the mass migration of its population into the neighboring countries has given rise to concerns of infectious disease spillover and escalation of arboviral spread in the region.

RESULTS

We performed phylogeographic analyses of dengue (DENV) and chikungunya (CHIKV) virus genomes sampled from a surveillance site in Ecuador in 2014-2015, along with genomes from the surrounding countries. Our results revealed at least two introductions of DENV, in 2011 and late 2013, that initially originated from Venezuela and/or Colombia. The introductions were subsequent to increases in the influx of Venezuelan and Colombian citizens into Ecuador, which in 2013 were 343% and 214% higher than in 2009, respectively. However, we show that Venezuela has historically been an important source of DENV dispersal in this region, even before the massive exodus of its population, suggesting already established paths of viral distribution. Like DENV, CHIKV was introduced into Ecuador at multiple time points in 2013-2014, but unlike DENV, these introductions were associated with the Caribbean. Our findings indicated no direct CHIKV connection between Ecuador, Colombia, and Venezuela as of 2015, suggesting that CHIKV was, at this point, not following the paths of DENV spread.

CONCLUSION

Our results reveal that Ecuador is vulnerable to arbovirus import from many geographic locations, emphasizing the need of continued surveillance and more diversified prevention strategies. Importantly, increase in human movement along established paths of viral dissemination, combined with regional outbreaks and epidemics, may facilitate viral spread and lead to novel virus introductions. Thus, strengthening infectious disease surveillance and control along migration routes and improving access to healthcare for the vulnerable populations is of utmost importance.

Climate change and viral emergence: evidence from Aedes-borne arboviruses

Climate change is leading to increases in global temperatures and erratic precipitation patterns, both of which are contributing to the expansion of mosquito-borne arboviruses and the populations of the mosquitos that vector them. Herein, we review recent evidence of emergence and expansion of arboviruses transmitted by Aedes mosquitos that has been driven in part by environmental changes. We present as a case study of recent work from Córdoba, Argentina, where dengue has been actively emerging in the past decade. We review recent empirical and modeling studies that aim to understand the impact of climate on future expansion of arboviruses, and we highlight gaps in empirical studies linking climate to arbovirus transmission at regional levels.

First report on seroprevalence and risk factors of dengue virus in Jordan

Background

There are no data available on dengue epidemiology in Jordan. This is the first study of the seroprevalence and risk factors of dengue virus (DENV) infection in Jordan.

Methods

Sera samples from 892 apparently healthy individuals from all over Jordan were tested for DENV by enzyme-linked immunosorbent assay and a validated questionnaire was completed by all participants to identify and rank possible risk factors.

Results

The seroprevalence was 24.6% (95% confidence interval 21.8 to 27.5). In univariate regression analysis, age, education, history of travel, living in rainy areas and practicing agriculture were significantly (p<0.05) associated with seropositivity. The multivariate logistic regression model showed that those who live in a rainy climate (odd ratio [OR] 1.7), are older (OR 2.3), have a history of international travel (OR 1.5) and are male with a history of international travel had a significantly greater odds of DENV seropositivity (OR 3.4).

Conclusions

These data suggest that DENV circulates in Jordan and that cases may be imported or locally transmitted. Further research is needed to determine the circulating DENV serotypes and vectors in Jordan. Given the high rate of DENV seropositivity, dengue should be considered as a differential diagnosis in febrile diseases in Jordan, especially among populations living in rainy climates.

Venezuela's humanitarian crisis, resurgence of vector-borne diseases, and implications for spillover in the region

In the past 5-10 years, Venezuela has faced a severe economic crisis, precipitated by political instability and declining oil revenue. Public health provision has been affected particularly. In this Review, we assess the impact of Venezuela's health-care crisis on vector-borne diseases, and the spillover into neighbouring countries. Between 2000 and 2015, Venezuela witnessed a 359% increase in malaria cases, followed by a 71% increase in 2017 (411 586 cases) compared with 2016 (240 613). Neighbouring countries, such as Brazil, have reported an escalating trend of imported malaria cases from Venezuela, from 1538 in 2014 to 3129 in 2017. In Venezuela, active Chagas disease transmission has been reported, with seroprevalence in children (<10 years), estimated to be as high as 12·5% in one community tested (n=64). Dengue incidence increased by more than four times between 1990 and 2016. The estimated incidence of chikungunya during its epidemic peak is 6975 cases per 100 000 people and that of Zika virus is 2057 cases per 100 000 people. The re-emergence of many vector-borne diseases represents a public health crisis in Venezuela and has the possibility of severely undermining regional disease elimination efforts. National, regional, and global authorities must take action to address these worsening epidemics and prevent their expansion beyond Venezuelan borders.

First dengue virus seroprevalence study on Madeira Island after the 2012 outbreak indicates unreported dengue circulation

Background

In 2012, the first dengue virus outbreak was reported on the Portuguese island of Madeira with 1080 confirmed cases. Dengue virus of serotype 1 (DENV-1), probably imported from Venezuela, caused this outbreak with autochthonous transmission by invasive Aedes aegypti mosquitoes.

Results

We investigated the seroprevalence among the population on Madeira Island four years after the outbreak. Study participants (n = 358), representative of the island population regarding their age and gender, were enrolled in 2012 in a cross-sectional study. Dengue antibodies were detected with an in-house enzyme-linked immunosorbent assay (ELISA) using the dimer of domain III (ED3) of the DENV-1 envelope protein as well as commercial Panbio indirect and capture IgG ELISAs. Positive ELISA results were validated with a neutralization test. The overall seroprevalence was found to be 7.8% (28/358) with the in-house ELISA, whereas the commercial DENV indirect ELISA detected IgG antibodies in 8.9% of the individuals (32/358). The results of the foci reduction neutralization test confirmed DENV-1 imported from South America as the causative agent of the 2012 epidemic. Additionally, we found a higher seroprevalence in study participants with an age above 60 years old and probable secondary DENV infected individuals indicating unreported dengue circulation before or after 2012 on Madeira Island.

Conclusions

This study revealed that the number of infections might have been much higher than estimated from only confirmed cases in 2012/2013. These mainly DENV-1 immune individuals are not protected from a secondary DENV infection and the majority of the population of Madeira Island is still naïve for DENV. Surveillance of mosquitoes and arboviruses should be continued on Madeira Island as well as in other European areas where invasive vector mosquitoes are present.

Electronic supplementary material

The online version of this article (10.1186/s13071-019-3357-3) contains supplementary material, which is available to authorized users.

Development and validation of four one-step real-time RT-LAMP assays for specific detection of each dengue virus serotype

BACKGROUND

4 one-step, real-time, reverse transcription loop-mediated isothermal amplification (RT-LAMP) assays were developed for the detection of dengue virus (DENV) serotypes by considering 2,056 full genome DENV sequences. DENV1 and DENV2 RT-LAMP assays were validated with 31 blood and 11 serum samples from Tanzania, Senegal, Sudan and Mauritania. DENV3 and DENV4 RT-LAMP assays were validated with 25 serum samples from Cambodia.

METHODOLOGY/PRINCIPAL FINDINGS

4 final reaction primer mixes were obtained by using a combination of Principal Component Analysis of the full DENV genome sequences, and LAMP primer design based on sequence alignments using the LAVA software. These mixes contained 14 (DENV1), 12 (DENV2), 8 (DENV3) and 3 (DENV4) LAMP primer sets. The assays were evaluated with an External Quality Assessment panel from Quality Control for Molecular Diagnostics. The assays were serotype-specific and did not cross-detect with other flaviviruses. The limits of detection, with 95% probability, were 22 (DENV1), 542 (DENV2), 197 (DENV3) and 641 (DENV4) RNA molecules, and 100% reproducibility in the assays was obtained with up to 102 (DENV1) and 103 RNA molecules (DENV2, DENV3 and DENV4). Validation of the DENV2 assay with blood samples from Tanzania resulted in 23 samples detected by RT-LAMP, demonstrating that the assay is 100% specific and 95.8% sensitive (positive predictive value of 100% and a negative predictive value of 85.7%). All serum samples from Senegal, Sudan and Mauritania were detected and 3 untyped as DENV1. The sensitivity of RT-LAMP for DENV4 samples from Cambodia did not quite match qRT-PCR.

CONCLUSIONS/SIGNIFICANCE

We have shown a novel approach to design LAMP primers that makes use of fast growing sequence databases. The DENV1 and DENV2 assays were validated with viral RNA extracted clinical samples, showing very good performance parameters.

Novel tools for the surveillance and control of dengue: findings by the DengueTools research consortium

BACKGROUND

Dengue fever persists as a major global disease burden, and may increase as a consequence of climate change. Along with other measures, research actions to improve diagnosis, surveillance, prevention, and predictive models are highly relevant. The European Commission funded the DengueTools consortium to lead a major initiative in these areas, and this review synthesises the outputs and findings of this work conducted from 2011 to 2016. Research areas: DengueTools organised its work into three research areas, namely [1] Early warning and surveillance systems; [2] Strategies to prevent dengue in children; and [3] Predictive models for the global spread of dengue. Research area 1 focused on case-studies undertaken in Sri Lanka, including developing laboratory-based sentinel surveillance, evaluating economic impact, identifying drivers of transmission intensity, evaluating outbreak prediction capacity and developing diagnostic capacity. Research area 2 addressed preventing dengue transmission in school children, with case-studies undertaken in Thailand. Insecticide-treated school uniforms represented an intriguing potential approach, with some encouraging results, but which were overshadowed by a lack of persistence of insecticide on the uniforms with repeated washing. Research area 3 evaluated potential global spread of dengue, particularly into dengue-naïve areas such as Europe. The role of international travel, changing boundaries of vectors, developing models of vectorial capacity under different climate change scenarios and strategies for vector control in outbreaks was all evaluated.

CONCLUDING REMARKS

DengueTools was able to make significant advances in methods for understanding and controlling dengue transmission in a range of settings. These will have implications for public health agendas to counteract dengue, including vaccination programmes.

OUTLOOK

Towards the end of the DengueTools project, Zika virus emerged as an unexpected epidemic in the central and southern America. Given the similarities between the dengue and Zika viruses, with vectors in common, some of the DengueTools thinking translated readily into the Zika situation.

Sentinel surveillance of imported dengue via travellers to Europe 2012 to 2014: TropNet data from the DengueTools Research Initiative

We describe the epidemiological pattern and genetic characteristics of 242 acute dengue infections imported to Europe by returning travellers from 2012 to 2014. The overall geographical pattern of imported dengue (South-east Asia > Americas > western Pacific region > Africa) remained stable compared with 1999 to 2010. We isolated the majority of dengue virus genotypes and epidemic lineages causing outbreaks and epidemics in Asia, America and Africa during the study period. Travellers acted as sentinels for four unusual dengue outbreaks (Madeira, 2012–13; Luanda, 2013; Dar es Salaam, 2014; Tokyo, 2014). We were able to characterise dengue viruses imported from regions where currently no virological surveillance data are available. Up to 36% of travellers infected with dengue while travelling returned during the acute phase of the infection (up to 7 days after symptom onset) or became symptomatic after returning to Europe, and 58% of the patients with acute dengue infection were viraemic when seeking medical care. Epidemiological and virological data from dengue-infected international travellers can add an important layer to global surveillance efforts. A considerable number of dengue-infected travellers are viraemic after arrival back home, which poses a risk for dengue introduction and autochthonous transmission in European regions where suitable mosquito vectors are prevalent.

Emerging arboviral human diseases in Southern Europe

Southern Europe is characterized by unique landscape and climate which attract tourists, but also arthropod vectors, some of them carrying pathogens. Among several arboviral diseases that emerged in the region during the last decade, West Nile fever accounted for high number of human cases and fatalities, while Crimean-Congo hemorrhagic fever expanded its geographic distribution, and is considered as a real threat for Europe. Viruses evolve rapidly and acquire mutations making themselves stronger and naive populations more vulnerable. In an effort to tackle efficiently the emerging arboviral diseases, preparedness and strategic surveillance are needed for the early detection of the pathogen and containment and mitigation of probable outbreaks. In this review, the main human arboviral diseases that emerged in Southern Europe are described.

The Epidemiological Characteristics and Dynamic Transmission of Dengue in China, 2013

Background

There was a dengue epidemic in several regions of China in 2013. No study has explored the dynamics of dengue transmission between different geographical locations with dengue outbreaks in China. The purpose of the study is to analyze the epidemiological characteristics and to explore the dynamic transmission of dengue in China, 2013.

Methodology and Principal Findings

Records of dengue cases of 2013 were obtained from the China Notifiable Disease Surveillance System. Full E-gene sequences of dengue virus detected from the outbreak regions of China were download from GenBank. Geographical Information System and heatmaps were used to describe the epidemiological characteristics. Maximum Likelihood phylogenetic and Bayesian phylogeographic analyses were conducted to explore the dengue dynamic transmission. Yunnan Province and Guangdong Province had the highest imported cases in the 2013 epidemic. In the locations with local dengue transmission, most of imported cases occurred from June to November 2013 while local dengue cases developed from July to December, 2013. There were significant variations for the incidences of dengue, in terms of age distributions, among different geographic locations. However, gender differences were identified in Guangzhou, Foshan and Xishuangbanna. DENV 1–3 were detected in all locations with the disease outbreaks. Some genotypes were detected in more than one locations and more than one genotypes have been detected in several locations. The dengue viruses introduced to outbreak areas were predominantly from Southeast Asia. In Guangdong Province, the phylogeographical results indicated that dengue viruses of DENV 1 were transmitted to neighboring cities Foshan and Zhongshan from Guangzhou city, and then transmitted to Jiangmen city. The virus in DENV 3 was introduced to Guangzhou city, Guangdong Province from Xishuangbanna prefecture, Yunnan Province.

Conclusions

Repeated dengue virus introductions from Southeast Asia and subsequent domestic dengue transmission within different regions may have contributed to the dengue epidemics in China, 2013.

Dengue is the most prevalent and rapidly spreading mosquito-borne viral disease. As an imported disease in China, the imported cases play a vital role for the local dengue transmission. There were dengue outbreaks in three Provinces (covering nine Cities/Prefectures) of China in 2013, with several regions had their first dengue outbreak in history including the one from central China. There has been no study so far to explore the dengue transmission dynamics between different regions in China. The purpose of the study is to describe the 2013 dengue epidemiological characteristics and to explore the transmission dynamics of dengue viruses between epidemic focus. The study results indicated that repeated dengue virus introductions from Southeast Asia and subsequent domestic dengue transmission within different regions may have contributed to the dengue epidemics in China, 2013. Population movement could have played a critical role in dengue dynamic transmission, which introduced dengue viruses to non-epidemic areas at broad or finer spatial scales. Therefore, it should be considered in the design of mosquito eradication campaign for dengue control and prevention.