The molecular and clinical features of dengue during outbreak in Jambi, Indonesia in 2015

Spatiotemporal Characterization of Dengue Incidence and Its Correlation to Climate Parameters in Indonesia

Dengue has become a public health concern in Indonesia since it was first found in 1968. This study aims to determine dengue hotspot areas and analyze the spatiotemporal distribution of dengue and its association with dominant climate parameters nationally. Monthly data for dengue and climate observations (i.e., rainfall, relative humidity, average, maximum, and minimum temperature) at the regency/city level were utilized. Dengue hotspot areas were determined through K-means clustering, while Singular Value Decomposition (SVD) determined dominant climate parameters and their spatiotemporal distribution. Results revealed four clusters: Cluster 1 comprised cities with medium to high Incidence Rates (IR) and high Case Densities (CD) in a narrow area. Cluster 2 has a high IR and low CD, and clusters 3 and 4 featured medium and low IR and CD, respectively. SVD analysis indicated that relative humidity and rainfall were the most influential parameters on IR across all clusters. Temporal fluctuations in the first mode of IR and climate parameters were clearly delineated. The spatial distribution of heterogeneous correlation between the first mode of rainfall and relative humidity to IR exhibited higher values, which were predominantly observed in Java, Bali, Nusa Tenggara, the eastern part of Sumatra, the southern part of Kalimantan, and several locations in Sulawesi.

Scrub typhus in Indonesia: A cross-sectional analysis of archived fever studies samples

BACKGROUND

Scrub typhus is an understudied vector-borne bacterial infection.

METHODS

We tested archived fever samples for scrub typhus seropositivity to begin charting its geographic distribution in Indonesia. We analysed 1033 serum samples from three sites. IgM and IgG enzyme-linked immunosorbent assay (ELISA) against Orientia tsutsugamushi was performed using Karp, Kato, Gilliam, TA 716 antigens. To determine the cutoff in the absence of a presumed unexposed population and gold standard tests, we identified the visual inflection point, performed change point analysis, and used finite mixture models.

RESULTS

The optical density cutoff values used for IgM and IgG were 0.49 and 0.13, respectively. Across all sites, IgM seropositivity was 4.6% (95% CI: 3.4 to 6.0%) while IgG seropositivity was 4.4% (95% CI: 3.3 to 5.8%). The overall seropositivity across sites was 8.8% (95% CI: 8.1 to 11.7%). The overall seropositivity for Jambi, Denpasar, Tabanan were 9.7% (95% CI: 7.0 to 13.3%), 8.0% (95% CI: 5.7 to 11.0%), 9.0% (95% CI: 6.1 to 13.0%), respectively.

CONCLUSIONS

We conclude that O. tsutsugamushi exposure in humans occurred at all sites analysed and could be the cause of illness in some cases. Though it was not the main cause of acute fever in these locations, it is still important to consider scrub typhus in cases not responding to beta-lactam antibiotics. Future seroprevalence surveys and testing for scrub typhus in acute febrile illness studies will be essential to understand its distribution and burden in Indonesia.

Mechanical transmission of dengue virus by Aedes aegypti may influence disease transmission dynamics during outbreaks

BACKGROUND

Dengue virus outbreaks are increasing in number and severity worldwide. Viral transmission is assumed to require a minimum time period of viral replication within the mosquito midgut. It is unknown if alternative transmission periods not requiring replication are possible.

METHODS

We used a mouse model of dengue virus transmission to investigate the potential of mechanical transmission of dengue virus. We investigated minimal viral titres necessary for development of symptoms in bitten mice and used resulting parameters to inform a new model of dengue virus transmission within a susceptible population.

FINDINGS

Naïve mice bitten by mosquitoes immediately after they took partial blood meals from dengue infected mice showed symptoms of dengue virus, followed by mortality. Incorporation of mechanical transmission into mathematical models of dengue virus transmission suggest that this supplemental transmission route could result in larger outbreaks which peak sooner.

INTERPRETATION

The potential of dengue transmission routes independent of midgut viral replication has implications for vector control strategies that target mosquito lifespan and suggest the possibility of similar mechanical transmission routes in other disease-carrying mosquitoes.

FUNDING

This study was funded by grants from the National Health Research Institutes, Taiwan (04D2-MMMOST02), the Human Frontier Science Program (RGP0033/2021), the National Institutes of Health (1R01AI143698-01A1, R01AI151004 and DP2AI152071) and the Ministry of Science and Technology, Taiwan (MOST104-2321-B-400-016).

Dengue seroprevalence study in Bali

INTRODUCTION

Dengue infection poses significant public health problems in tropical and subtropical regions worldwide. The clinical manifestations of dengue vary from asymptomatic to severe dengue manifestations. This serological survey highlighted the high incidence of asymptomatic cases. This study aimed to determine the prevalence of dengue in healthy and ill adults in Bali.

METHODS

Cross-sectional seroprevalence surveys were performed between July 2020 and June 2021 among healthy and ill adults in Denpasar Bali. Blood samples were collected from 539 randomly selected urban sites in Denpasar. Immunoglobulin G antibodies against the dengue virus were detected in serum using a commercial enzyme-linked immunosorbent assay kit.

RESULTS

Overall, the dengue seroprevalence rate among the 539 clinically healthy and ill adults was high (85.5%). The median age was 34.1 (18-86.1). Most of the participants in the study were younger than 40 years (61.2%). Men were the dominant sex (54.5%). The study found a significant association between dengue seropositivity among people aged > 40 years and healthy status (p = 0.005; odds ratio [OR] = 0.459 and p < 0.001; OR = 0.336, respectively). The study reported that as many as 60% of the subjects had a history of previously suspected dengue infection. This study reflected the proportion of asymptomatic dengue patients requiring better assessment with a serological test.

CONCLUSION

The current study highlighted that real cases of dengue infection may be higher than reported, with a high prevalence of dengue seropositivity and a relatively dominant proportion of asymptomatic cases. The study guides physicians to be aware of every dengue infection in tropical countries and prevent the spread of the disease.

Genetic Analysis of Dengue Virus in Severe and Non-Severe Cases in Dhaka, Bangladesh, in 2018-2022

Dengue virus (DENV) infections have unpredictable clinical outcomes, ranging from asymptomatic or minor febrile illness to severe and fatal disease. The severity of dengue infection is at least partly related to the replacement of circulating DENV serotypes and/or genotypes. To describe clinical profiles of patients and the viral sequence diversity corresponding to non-severe and severe cases, we collected patient samples from 2018 to 2022 at Evercare Hospital Dhaka, Bangladesh. Serotyping of 495 cases and sequencing of 179 cases showed that the dominant serotype of DENV shifted from DENV2 in 2017 and 2018 to DENV3 in 2019. DENV3 persisted as the only representative serotype until 2022. Co-circulation of clades B and C of the DENV2 cosmopolitan genotype in 2017 was replaced by circulation of clade C alone in 2018 with all clones disappearing thereafter. DENV3 genotype I was first detected in 2017 and was the only genotype in circulation until 2022. We observed a high incidence of severe cases in 2019 when the DENV3 genotype I became the only virus in circulation. Phylogenetic analysis revealed clusters of severe cases in several different subclades of DENV3 genotype I. Thus, these serotype and genotype changes in DENV may explain the large dengue outbreaks and increased severity of the disease in 2019.

Genetic characterization of dengue virus 4 complete genomes from East Java, Indonesia

Dengue is an endemic arboviral disease with continuous transmission in Indonesia for more than five decades. A recent outbreak in Jember, East Java province, demonstrated the predominance of DENV-4, a serotype known for its low global spread and limited transmission. While epidemiological factors such as new serotype introduction and lacking herd immunity may explain its predominance, viral factors may also contribute. Using next-generation sequencing, we generated 13 representative complete genomes of DENV-4 responsible for the outbreak. Phylogenetic and evolutionary analyses on complete genomes were performed to understand the spatial and temporal dynamics of the viruses. Further analyses were done to study amino acid variations in DENV genes, as well as the potential events of recombination and selection pressure within the genomes. We revealed the DENV-4 genetic factors that may lead to its predominance in the 2019 Jember dengue outbreak. A combination of selection pressure and mutational genetic changes may contribute to the DENV-4 predominance in East Java, Indonesia. The possible intra-serotype recombination events involving the non-structural protein 5 (NS5) gene were also observed. Altogether, these genetic factors may act as additional factors behind the complex dengue outbreak mechanism.

Dengue virus population genetics in Yogyakarta, Indonesia prior to city-wide Wolbachia deployment

Dengue has been endemic in Yogyakarta, Indonesia for decades. Here, we report the dengue epidemiology, entomology, and virology in Yogyakarta in 2016-2017, prior to the commencement of the Applying Wolbachia to Eliminate Dengue (AWED) randomized trial. Dengue epidemiological data were compiled and blood samples from dengue-suspected patients were tested for dengue virus (DENV). Ae. aegypti mosquito samples were caught from the field using BG-Sentinel traps and tested for the presence of DENV infection. Sequencing of the DENV E gene was used to determine the phylogeny and genotypes of circulating DENV. Within the last decade, the 2016-2017 dengue incidence was considered very high. Among the 649 plasma samples collected between March 2016-February 2017; and 36,910 mosquito samples collected between December 2016-May 2017, a total of 197 and 38 samples were DENV-positive by qRT-PCR, respectively. All four DENV serotypes were detected, with DENV-3 (n = 88; 44.67%) and DENV-1 (n = 87; 44.16%) as the predominant serotype, followed by DENV-4 (n = 12; 6.09%) and DENV-2 (n = 10; 5.08%). The Yogyakarta DENV-1 isolates were classified into Genotype I and IV, while DENV-2, DENV-3, and DENV-4 isolates were classified into the Cosmopolitan genotype, Genotype I, and Genotype II, respectively. Yogyakarta DENV isolates were closely related to Indonesian strains from neighboring Javanese cities, consistent with the endemic circulation of DENV on this highly populous island. Our study provides comprehensive baseline information on the DENV population genetic characteristics in Yogyakarta, which are useful as baseline data for the AWED trial and the future DENV surveillance in the city in the presence of a Wolbachia-infected Ae. aegypti population.

Hyperendemic Dengue and Possible Zika Circulation in the Westernmost Region of the Indonesian Archipelago

The transmission of dengue and other medically important mosquito-borne viruses in the westernmost region of Indonesia is not well described. We assessed dengue and Zika virus seroprevalence in Aceh province, the westernmost area of the Indonesian archipelago. Serum samples collected from 199 randomly sampled healthy residents of Aceh Jaya in 2017 were analyzed for neutralizing antibodies by plaque reduction neutralization test (PRNT). Almost all study participants (198/199; 99.5%) presented with multitypic profiles of neutralizing antibodies to two or more DENV serotypes, indicating transmission of multiple DENV in the region prior to 2017. All residents were exposed to one or more DENV serotypes by the age of 30 years. The highest geometric mean titers were measured for DENV-4, followed by DENV-1, DENV-2 and DENV-3. Among a subset of 116 sera, 27 neutralized ZIKV with a high stringency (20 with PRNT₉₀ > 10 and 7 with PRNT₉₀ > 40). This study showed that DENV is hyperendemic in the westernmost region of the Indonesian archipelago and suggested that ZIKV may have circulated prior to 2017.

Co-Circulation of Chikungunya and Multiple DENV Serotypes and Genotypes, Western Indonesia 2015-2016

Dengue is a mosquito-borne disease of public health concern affecting tropical and subtropical countries, including Indonesia. Although studies on dengue epidemiology have been undertaken in Indonesia, data are lacking in many areas of the country. The aim of this study was to determine dengue virus (DENV) and chikungunya virus (CHIKV) molecular epidemiology in western regions of the Indonesian archipelago. A one-year prospective study was conducted in Aceh and Jambi in 2015 and 2016, respectively, where patients with dengue-like illness were enrolled. Of 205 patients recruited, 29 and 27 were confirmed with dengue in Aceh and Jambi, respectively, and three from Jambi were confirmed with chikungunya. DENV-1 was the predominant serotype identified in Aceh while DENV-2 was predominant in Jambi. All DENV-1 and DENV-2 from both regions were classified as Genotype I and Cosmopolitan genotype, respectively, and all DENV-3 viruses from Jambi were Genotype I. Some viruses, in particular DENV-1, displayed a distinct lineage distribution, where two DENV-1 lineages from Aceh were more closely related to viruses from China instead of Jambi highlighting the role of travel and flight patterns on DENV transmission in the region. DENV-2 from both Aceh and Jambi and DENV-3 from Jambi were all closely related to Indonesian local strains. All three CHIKV belonged to Asian genotype and clustered closely with Indonesian CHIKV strains including those previously circulating in Jambi in 2015, confirming continuous and sustainable transmission of CHIKV in the region. The study results emphasize the importance of continuous epidemiological surveillance of arboviruses in Indonesia and simultaneous testing for CHIKV among dengue-suspected patients.

Molecular epidemiology of dengue in a setting of low reported endemicity: Kupang, East Nusa Tenggara province, Indonesia

BACKGROUND

Most regions in Indonesia experience annual dengue epidemics. However, the province of East Nusa Tenggara has consistently reported low incidence. We conducted a dengue molecular epidemiology study in Kupang, the capital of the province.

METHODS

Dengue patients were recruited from May 2016 to September 2017. Dengue virus (DENV) screening was performed using NS1 and immunoglobulin G (IgG)/IgM detection. Serotype was determined using reverse transcription polymerase chain reaction and the envelope genes were sequenced to infer the genetic identity and phylogeny.

RESULTS

From 119 patients, dengue was confirmed in 62 (52%). Compared with official data, underreporting of dengue incidence was observed. The majority (36%) of patients were children <10 y of age. Most patients (80%) experienced mild fever. All serotypes were detected, with DENV-3 as the predominant (57%). Kupang DENV-1 isolate was classified as genotype IV, an old and endemic strain, DENV-2 as cosmopolitan, DENV-3 as genotype I and DENV-4 as genotype II. Most isolates showed relatively low evolutionary rates and are closely related with strains from Bali and Timor Leste.

CONCLUSIONS

The low dengue incidence was most likely caused by sustained local circulation of endemic viruses. This study provides information on the epidemiology of dengue in a low-endemicity setting that should help future mitigation and disease management.

Dengue virus in humans and mosquitoes and their molecular characteristics in northeastern Thailand 2016-2018

Dengue is hyperendemic in most Southeast Asian countries including Thailand, where all four dengue virus serotypes (DENV-1 to -4) have circulated over different periods and regions. Despite dengue cases being annually reported in all regions of Thailand, there is limited data on the relationship of epidemic DENV infection between humans and mosquitoes, and about the dynamics of DENV during outbreaks in the northeastern region. The present study was conducted in this region to investigate the molecular epidemiology of DENV and explore the relationships of DENV infection in humans and in mosquitoes during 2016–2018. A total of 292 dengue suspected patients from 11 hospitals and 902 individual mosquitoes (at patient’s houses and neighboring houses) were recruited and investigated for DENV serotypes infection using PCR. A total of 103 patients and 149 individual mosquitoes were DENV -positive. Among patients, the predominant DENV serotypes in 2016 and 2018 were DENV-4 (74%) and DENV-3 (53%) respectively, whereas in 2017, DENV-1, -3 and -4 had similar prevalence (38%). Additionally, only 19% of DENV infections in humans and mosquitoes at surrounding houses were serotypically matched, while 81% of infections were serotypically mismatched, suggesting that mosquitoes outside the residence may be an important factor of endemic dengue transmission. Phylogenetic analyses based on envelope gene sequences showed the genotype I of both DENV-1 and DENV-4, and co-circulation of the Cosmopolitan and Asian I genotypes of DENV-2. These strains were closely related to concurrent strains in other parts of Thailand and also similar to strains in previous epidemiological profiles in Thailand and elsewhere in Southeast Asia. These findings highlight genomic data of DENV in this region and suggest that people’s movement in urban environments may result in mosquitoes far away from the residential area being key determinants of DENV epidemic dynamics.

Molecular epidemiology of dengue in North Kalimantan, a province with the highest incidence rates in Indonesia in 2019

OBJECTIVES

Dengue is endemic to Indonesia, a country that has largely varied geographical and demographic conditions across different regions. In 2019, dengue epidemic occurred in North Kalimantan province and recorded as the highest incidence rate in Indonesia. This study aims to investigate the molecular epidemiology of dengue during outbreak in the province and compare the epidemiological characteristics between two cities/towns in North Kalimantan, namely Malinau, an inland town surrounded by a dense rainforest, and Tarakan, an island city.

METHODS

A cross sectional study was conducted between September 2018 and July 2019. Dengue-like illness patients were recruited in hospitals and tested for dengue NS1 and IgG/IgM. Serological prevalence was measured using IgG ELISA, dengue virus (DENV) serotyping was conducted using RT-PCR and Envelope gene sequencing was performed to infer the virus origins and phylogeny. Clinical, demographical, and diagnostics data were also recorded and analyzed.

RESULTS

We recruited 523 patients, 261 from Malinau and 262 from Tarakan. Among them, 349 patients were confirmed dengue. Cases in Malinau had a higher proportion of confirmed dengue (82.0%) compared to those in Tarakan (51.5%). Cases in Malinau were more likely to be dengue hemorrhagic fever with more severe hematological features compared to those in Tarakan. All four DENV serotypes were detected in both cities, the most prevalent serotype being DENV-2. The genetic characteristics of the viruses in the two towns was similar except for DENV-3. No sylvatic DENV was detected as well as alphaviruses and non-dengue flaviviruses during the outbreak.

CONCLUSIONS

The molecular epidemiology of dengue in North Kalimantan revealed the similar virological characteristics but different clinical and demographic aspects in Malinau and Tarakan. The distinct dengue dynamics between different regions of Indonesia is prominent and this knowledge will be important for understanding future patterns of DENV transmission in the region.

Comparative cytokine profiling identifies common and unique serum cytokine responses in acute chikungunya and dengue virus infection

Background

Infection by chikungunya (CHIKV) and dengue virus (DENV) can cause a wide spectrum of clinical features, many of which are undifferentiated. Cytokines, which broadly also include chemokines and growth factors, have been shown to play a role in protective immunity as well as DENV and CHIKV pathogenesis. However, differences in cytokine response to both viruses remain poorly understood, especially in patients from countries where both viruses are endemic. Our study is therefore aimed to provide a comparative profiling of cytokine response induced by acute DENV and CHIKV infections in patients with similar disease stages and in experimental in vitro infections.

Methods

By using multiplex immunoassay, we compared host cytokine profiles between acute CHIKV and DENV infections by analysing serum cytokine levels of IL-1α, IL-4, IL-5, IL-8, IL-13, RANTES, MCP-3, eotaxin, PDGF-AB/BB, and FGF-2 from the sera of acute chikungunya and dengue fever patients. We further investigated the cytokine profile responses using experimental in vitro CHIKV and DENV infections of peripheral blood mononuclear cells (PBMCs).

Results

We found that both CHIKV and DENV-infected patients had an upregulated level of IL-8 and IL-4, with the highest IL-4 level observed in DENV-2 infected patients. Higher IL-8 level was also correlated with lower platelet count in dengue patients. IL-13 and MCP-3 downregulation was observed only in chikungunya patients, while conversely PDGF-AB/BB and FGF-2 downregulation was unique in dengue patients. Age-associated differential expression of IL-13, MCP-3, and IL-5 was also observed, while distinct kinetics of IL-4, IL-8, and FGF-2 expression between CHIKV and DENV-infected patients were identified. Furthermore, the unique pattern of IL-8, IL-13 and MCP-3, but not IL-4 expression was also recapitulated using experimental in vitro infection in PBMCs.

Conclusions

Taken together, our study identified common cytokine response profile characterized by upregulation of IL-8 and IL-4 between CHIKV and DENV infection. Downregulation of IL-13 and MCP-3 was identified as a unique cytokine response profile of acute CHIKV infection, while distinct downregulation of PDGF-AB/BB and FGF-2 characterized the response from acute DENV infection. Our study provides an important overview of the host cytokine responses between CHIKV and DENV infection, which is important to further understand the mechanism and pathology of these diseases.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-06339-6.

Evolution, heterogeneity and global dispersal of cosmopolitan genotype of Dengue virus type 2

Dengue virus type 2 (DENV-2) contributes substantially to the dengue burden and dengue-related mortality in the tropics and sub-tropics. DENV-2 includes six genotypes, among which cosmopolitan genotype is the most widespread. The present study investigated the evolution, intra-genotype heterogeneity and dispersal of cosmopolitan genotype to understand unique genetic characteristics that have shaped the molecular epidemiology and distribution of cosmopolitan lineages. The spatial analysis demonstrated a wide geo-distribution of cosmopolitan genotype through an extensive inter-continental network, anchored in Southeast Asia and Indian sub-continent. Intra-genotype analyses using 3367 envelope gene sequences revealed six distinct lineages within the cosmopolitan genotype, namely the Indian sub-continent lineage and five other lineages. Indian sub-continent lineage was the most diverged among six lineages and has almost reached the nucleotide divergence threshold of 6% within E gene to qualify as a separate genotype. Genome wide amino acid signatures and selection pressure analyses further suggested differences in evolutionary characteristics between the Indian sub-continent lineage and other lineages. The present study narrates a comprehensive genomic analysis of cosmopolitan genotype and presents notable genetic characteristics that occurred during its evolution and global expansion. Whether those characteristics conferred a fitness advantage to cosmopolitan genotype in different geographies warrant further investigations.

Epidemiology and challenges of dengue surveillance in the WHO South-East Asia Region

Dengue poses a significant health and economic burden in the WHO South-East Asia Region. Approaches for control need to be aligned with current knowledge on the epidemiology of dengue in the region. Such knowledge will ensure improved targeting of interventions to reduce dengue incidence and its socioeconomic impact. This review was undertaken to describe the contemporary epidemiology of dengue and critically analyse the existing surveillance strategies in the region. Over recent decades, dengue incidence has continued to increase with geographical expansion. The region has now become hyper-endemic for multiple dengue virus serotypes/genotypes. Every epidemic cycle was associated with a change of predominant serotype/genotype and this was often associated with severe disease with intense transmission. Classical larval indices are widely used in vector surveillance and adult mosquito samplings are not implemented as a part of routine surveillance. Further, there is a lack of integration of entomological and disease surveillance systems, often leading to inaction or delays in dengue prevention and control. Disease surveillance does not capture all cases, resulting in under-reporting, and has thus failed to adequately represent the true burden of disease in the region. Possible solutions include incorporating adult mosquito sampling into routine vector surveillance, the establishment of laboratory-based sentinel surveillance, integrated vector and dengue disease surveillance and climate-based early warning systems using available technologies like mobile apps.

Aggressive organ penetration and high vector transmissibility of epidemic dengue virus-2 Cosmopolitan genotype in a transmission mouse model

Dengue virus (DENV) causes dengue fever and severe hemorrhagic fever in humans and is primarily transmitted by Aedes aegypti and A. albopictus mosquitoes. The incidence of DENV infection has been gradually increasing in recent years due to global urbanization and international travel. Understanding the virulence determinants in host and vector transmissibility of emerging epidemic DENV will be critical to combat potential outbreaks. The DENV serotype 2 (DENV-2), which caused a widespread outbreak in Taiwan in 2015 (TW2015), is of the Cosmopolitan genotype and is phylogenetically related to the virus strain linked to another large outbreak in Indonesia in 2015. We found that the TW2015 virus was highly virulent in type I and type II interferon-deficient mice, with robust replication in spleen, lung, and intestine. The TW2015 virus also had high transmissibility to Aedes mosquitoes and could be effectively spread in a continuous mosquitoes-mouse-mosquitoes-mouse transmission cycle. By making 16681-based mutants carrying different segments of the TW2015 virus, we identified the structural pre-membrane (prM) and envelope (E) genes as key virulence determinants in the host, with involvement in the high transmissibility of the TW2015 virus in mosquitoes. The transmission mouse model will make a useful platform for evaluation of DENV with high epidemic potential and development of new strategies against dengue outbreaks.

Distinct Dengue Disease Epidemiology, Clinical, and Diagnosis Features in Western, Central, and Eastern Regions of Indonesia, 2017-2019

The people of Indonesia have been afflicted by dengue, a mosquito-borne viral disease, for over 5 decades. The country is the world's largest archipelago with diverse geographic, climatic, and demographic conditions that may impact the dynamics of disease transmissions. A dengue epidemiology study was launched by us to compare and understand the dynamics of dengue and other arboviral diseases in three cities representing western, central, and eastern Indonesia, namely, Batam, Banjarmasin, and Ambon, respectively. A total of 732 febrile patients were recruited with dengue-like illness during September 2017-2019 and an analysis of their demographic, clinical, and virological features was performed. The seasonal patterns of dengue-like illness were found to be different in the three regions. Among all patients, 271 (37.0%) were virologically confirmed dengue, while 152 (20.8%) patients were diagnosed with probable dengue, giving a total number of 423 (57.8%) dengue patients. Patients' age and clinical manifestations also differed between cities. Mostly, mild dengue fever was observed in Batam, while more severe cases were prominent in Ambon. While all dengue virus (DENV) serotypes were detected, distinct serotypes dominated in different locations: DENV-1 in Batam and Ambon, and DENV-3 in Banjarmasin. We also assessed the diagnostic features in the study sites, which revealed different patterns of diagnostic agreements, particularly in Ambon. To detect the possibility of infection with other arboviruses, further testing on 461 DENV RT-PCR-negative samples was performed using pan-flavivirus and -alphavirus RT-PCRs; however, only one chikungunya infection was detected in Ambon. A diverse dengue epidemiology in western, central, and eastern Indonesia was observed, which is likely to be influenced by local geographic, climatic, and demographic conditions, as well as differences in the quality of healthcare providers and facilities. Our study adds a new understanding on dengue epidemiology in Indonesia.

Antiviral Action of Curcumin Encapsulated in Nanoemulsion against Four Serotypes of Dengue Virus

BACKGROUND

Curcumin has been used as a traditional medicine showing antiinflammatory, antimicrobial, and antiviral properties. Despite the promising potentials, curcumin-based drug development is hindered due to its poor solubility and cell uptake.

OBJECTIVE

This study aims to produce curcumin nanoemulsion (nanocurcumin) and evaluate its physical characteristics and in vitro cell cytotoxicity and antiviral activity against dengue virus (DENV).

METHODS

Nanocurcumin was generated by self-nanoemulsion technique. Cytotoxicity was determined using MTT assay in A549 cell line. Anti-DENV properties were determined by calculation of inhibitory concentration 50 (IC50) and plaque assay.

RESULTS

The resulting nanoemulsion showed uniform droplet size distribution with the average droplet size of 40.85 ± 0.919 nm. Nanocurcumin exhibited higher cell cytotoxicity compared to curcumin solution and may be explained by better cell uptake. Nanocurcumin treatment suppressed DENV growth, although no significant difference observed compared to the curcumin solution counterpart. Greater virus reduction was observed for DENV-1 and DENV-2.

CONCLUSION

The synthesis of nanocurcumin improved curcumin physicochemical properties with potential as antiviral against DENV.

Dengue Virus Serotype 4 Is Responsible for the Outbreak of Dengue in East Java City of Jember, Indonesia

Outbreaks of dengue virus (DENV) in Indonesia have been mainly caused by the DENV serotype-1; -2; or -3. The DENV-4 was the least-reported serotype in Indonesia during the last five decades. We recently conducted a molecular epidemiology study of dengue in the Jember regency, East Java province, Indonesia. Dengue is endemic in the region and outbreaks occur annually. We investigated the clinical characteristics and etiology of dengue-like febrile illness in this regency to understand the disease dynamics. A total of 191 patients with clinical symptoms similar to dengue were recruited during an 11-month study in 2019-2020. Children accounted for the majority of cases and dengue burden was estimated in 41.4% of the cases based on NS1 antigen, viral RNA, and IgG/IgM antibody detection with the majority (73.4%) being primary infections. Secondary infection was significantly associated with a higher risk of severe dengue manifestation. All four DENV serotypes were detected in Jember. Strikingly, we observed the predominance of DENV-4, followed by DENV-3, DENV-1, and DENV-2. Genotype determination using Envelope gene sequence revealed the classification into Genotype I, Cosmopolitan Genotype, Genotype I, and Genotype II for DENV-1, -2, -3, and -4, respectively. The predominance of DENV-4 in Jember may be associated with a new wave of DENV infections and spread in a non-immune population lacking a herd-immunity to this particular serotype.

Circulation of Various Dengue Serotypes in a Community-Based Study in Jakarta, Indonesia

Dengue virus (DENV) infection remains to be a serious health problem in Indonesia. Community-based dengue studies to determine circulating DENV serotypes based on the geography and season are limited owing to the expensive cost and significant effort required. Many patients with DENV infection are not hospitalized and many visit the hospital in the later phase of the disease. In this study, we performed active DENV surveillance in a community in Jakarta to study the circulating dengue serotypes; adult febrile patients with fever less than 48 hours were recruited. Disease severity was defined using the World Health Organization (WHO) 1997 guidelines. Rapid NS1 dengue antigen detection was used to screen patients with DENV in the community. Viral culture using the C6/36 cell line, an increased antibody titer on hemagglutination inhibition test and enzyme linked immunosorbent assay, or detection of the viral genome on reverse transcription-polymerase chain reaction was used to confirm DENV infection. Of the 102 patients, 68 (66.7%) were confirmed to have DENV infection, with DENV-2 being the most dominant serotype, followed by DENV-3, DENV-1, and DENV-4, in concordance with several reports of mixed DENV infection. Interestingly, in terms of disease severity, although DENV-3 infection was not the predominant circulating serotype, infection with it tended to cause a more severe disease than infection with DENV-2.

Clinical features and virological confirmation of perinatal dengue infection in Jambi, Indonesia: A case report

The hyper-endemicity of dengue in Indonesia poses a significant threat of dengue virus (DENV) vertical transmission during pregnancy. A 29-year-old female at 38 weeks of pregnancy presented to hospital with acute fever and later confirmed with DENV infection. Due to signs of fetal distress, the neonate was delivered by emergency caesarean section. The mother developed a dengue critical phase post-caesarean with excessive bleeding and required blood transfusion. During the 6th day of life, the neonate was diagnosed and later confirmed with dengue. Next-generation sequencing of DENV RNA isolated directly from sera of both mother and neonate revealed identical DENV-2 whole-genome sequences. Plaque reduction neutralization test (PRNT) detected anti-dengue antibodies in both mother and neonate. Altogether, our data confirmed the occurrence of vertical transmission. Dengue vertical transmission during pregnancy may lead to severe manifestation, hence early diagnosis, close monitoring, and prompt intervention are critical.

Multiple introductions of dengue virus strains contribute to dengue outbreaks in East Kalimantan, Indonesia, in 2015-2016

BACKGROUND

Dengue fever is a febrile disease caused by dengue virus (DENV), which affects people throughout the tropical and subtropical regions of the world, including Indonesia. East Kalimantan (Borneo) province suffered a dramatic increase in dengue cases in 2015 and 2016, making it the province with the second highest incidence of dengue in Indonesia. Despite this, dengue in East Kalimantan is understudied; leaving transmission dynamics of the disease in the area are mostly unknown. In this study, we investigate the factors contributing to the outbreaks in East Kalimantan.

METHODS

Prospective clinical and molecular virology study was conducted in two main cities in the province, namely Samarinda and Balikpapan, in 2015-2016. Patients' clinical, hematological, and demographic data were recorded. Dengue detection and confirmation was performed using NS1-antigen and IgG/IgM antibody detection. RT-PCR was conducted to determine the serotypes of the virus. Phylogenetic analysis was performed based on envelope gene sequences.

RESULTS

Three hundred patients with suspected dengue were recruited. Among these, 132 (44%) were diagnosed with dengue by NS1 antigen and/or nucleic acid detection. The majority of the infections (60%) were primary, with dengue hemorrhagic fever (DHF) the predominant manifestation (71.9%). Serotyping detected all four DENV serotypes in 112 (37.3%) cases, with the majority of patients (58.9%) infected by DENV-3. Phylogenetic analysis based on envelope gene sequences revealed the genotypes of the viruses as DENV-1 Genotype I, DENV-2 Cosmopolitan, and DENV-3 Genotype I. Most virus strains were closely-related to strains from cities in Indonesia.

CONCLUSIONS

Our observations indicate that multiple introductions of endemic DENV from surrounding cities in Indonesia, coupled with relatively low herd immunity, were likely responsible for the outbreak of the dominant viruses. The study provides information on the clinical spectrum of the disease, together with serology, viral genetics, and demographic data, which will be useful for better understanding of dengue disease in Borneo.

Genotype replacement of dengue virus type 3 and clade replacement of dengue virus type 2 genotype Cosmopolitan in Dhaka, Bangladesh in 2017

Dengue is a mosquito-borne disease that has spread to >100 countries and is caused by the dengue virus (DENV), which belongs to the Flavivirus genus of the family Flaviviridae. DENV comprises 4 serotypes (DENV-1 to -4), and each serotype is further divided into distinct genotypes. In India, it is reported that all 4 serotypes of DENV co-circulate. Although Bangladesh is a neighboring country of India, very few reports have published DENV sequence data for the country, especially after 2012. To understand the current distribution of DENV genotypes in Bangladesh, we determined the nucleotide sequences of envelope regions obtained from 58 DENV-positive patients diagnosed at Apollo Hospitals Dhaka during the period between September 2017 and February 2018. We found 5 DENV-1, 47 DENV-2, and 6 DENV-3 serotypes. A phylogenetic analysis of the obtained viral sequences revealed that DENV-3 genotype I was present instead of DENV-3 genotype II, which was predominant in Bangladesh between 2000 and 2009. Furthermore, we found two distinct lineages of the Cosmopolitan genotype of DENV-2, one of which was closely related to strains from Southeast Asia and has never been reported previously in Bangladesh. These results indicated that DENVs in Bangladesh have increased in genotypic diversity and suggest that the DENV genotypic shift observed in other Asian countries also might have been taking place in Bangladesh.

Epidemiology of dengue hemorrhagic fever in Indonesia: analysis of five decades data from the National Disease Surveillance

Objective

To provide a national incidence rate and case fatality rate of dengue hemorrhagic fever in Indonesia through an analysis of the National Disease Surveillance database from the Directorate General of Disease Prevention and Control of Ministry of Health.

Results

Available data has indicated an increasing trend of dengue hemorrhagic fever incidence in Indonesia over the past 50 years. Incidence rates appear to be cyclic, peaking approximately every 6–8 years. In contrast, the case fatality rate has decreased approximately by half each decade, since 1980. Java Island contributed the highest average number of dengue hemorrhagic fever cases each year. In recent years, Bali and Borneo (Kalimantan) have had the highest incidence while Papua Island, the easternmost region of the Indonesian archipelago, has had the lowest incidence.

Concurrent infections of dengue virus serotypes in Bali, Indonesia

Objective

To describe cases of dengue virus (DENV) concurrent infections in patients from both local and international traveler visiting Bali, Indonesia.

Results

During a hospital-based study, 260 patients (from 161 local and 99 international traveler patients) were recruited. Among them, 190 were positive by DENV RT-PCR in which eight patients (five local and three international travelers) detected as having concurrent infections by two different DENV serotypes. Among the eight patients, the common dengue symptoms diagnosed were fever, headache, and myalgia. Six cases (75%) were diagnosed with dengue fever (DF) while two cases (25%) manifested with bleeding and were diagnosed with dengue hemorrhagic fever (DHF) grade 1. The DENVs concurrent infections involved all four DENV serotypes known to be circulating in Bali. Although cases of DENV concurrent infections have been implicated with severe manifestation, we observed that most of concurrent infections cases in our study were of mild clinical manifestation, that may be related to the changing of DENV serotype predominance which is occurring in Bali, Indonesia.

Epidemiological profile of dengue in Zhejiang Province, southeast China

BACKGROUND

Dengue is one of the most important vector-bore infectious diseases in China because of its drastic increase in incidence, geographic extension and profound influence on China's economy. This study aims to retrospectively uncover the epidemiological profile of dengue in Zhejiang, one of the most developed provinces in China, and to find the problem existing in dengue control and prevention.

METHODOLOGY

Descriptive analyses on the dengue incidence and associated factors were performed. We also identified potential space-time cluster and generated the risk map of dengue.

PRINCIPAL FINDINGS

A total of 529 cases were reported in Zhejiang Province from 2005 to 2016, and 44.4% were imported. 67.7% of cases were 25~60 years old and the overall male-to-female sex ratio was 1.09:1. Dengue was reported all year round and 70.7% of cases occurred between August and October. Indigenous cases were only reported in the period between July to November and more than half occurred in September. Geographically, dengue was most distributed in Jinghua (3.62 per million), Shaoxing (1.00 per million) and Taizhou (0.81 per million) prefecture level cities. Outbreaks were confirmed in Yiwu, Keqiao and Huangyan counties in 2009, 2015, and 2016, respectively. 73.9% cases would seek medical advice within two days after onset and be confirmed within 9 days after onset. 75.6% would be recognized as dengue within 8 days after their first visit. The time intervals between onset and confirmation (median 7 vs 6 days; Wilcoxon rank sum test Z = -2.40, P = 0.016), first visit and confirmation (median 7 vs 6 days; Wilcoxon rank sum test Z = -2.59, P = 0.009) of indigenous cases were significantly longer than those of imported ones. However, the time intervals between onset and first visit for indigenous cases was shorter (median 0 vs 1 days; Wilcoxon rank sum test Z = -2.10, P = 0.036). Fever (99.1%), fatigue (81.9), rash (63.7%), headache (67.2%) and myalgia (52.60%) were the most frequently mentioned symptoms.

CONCLUSIONS

Zhejiang has recently witnessed an increase in incidence and geographic extension of dengue. Timely diagnosis is important to stop local transmission and outbreak.

Co-circulation of four dengue serotypes at South Eastern Andhra Pradesh, India: A prospective study

Background

Dengue is one of the most important mosquito-borne viral diseases in the world. The emergence and spread of four dengue viruses (DENVs) (serotypes) represent a global pandemic. The four distinct serotypes are, namely, DENV-1, DENV-2, DENV-3 and DENV-4. Very few dengue serotyping studies have been reported from Andhra Pradesh. In this context, the present study focuses on the circulating serotypes of dengue in South-Eastern Andhra Pradesh.

Methodology

Study was done at Sri Venkateswara Institute of Medical Sciences, a teaching hospital in Tirupati, Andhra Pradesh. Acute phase dengue serum samples were collected and tested for NS1 antigen and anti-human IgM antibodies by enzyme-linked immunosorbent assay (ELISA). NS1-positive samples were further serotyped by reverse transcriptase real-time polymerase chain reaction (rRT-PCR).

Results

A total of 398 serum samples were received from clinically suspected dengue fever cases. Of these, 150 (37.7%) samples were positive for NS1 and/or IgM ELISA. The 96 NS1 antigen-positive samples were further processed for serotyping, of which 36 were negative by rRT-PCR. DENV-2 (41%) was the predominant serotype, followed by DENV-4 (37%), DENV-3 (12%) and DENV-1 (10%) in descending order.

Conclusion

This study reports the all four dengue serotypes' co-circulation. This is the first report from South Eastern Andhra Pradesh. Amongst four, DENV-2 was predominant followed by DENV-4. The information of predominant serotypes can guide in forecasting dengue outbreaks and improving control measures of vectors thus may be helpful in the prevention of outbreaks.

Molecular characterization and phylogenetic analysis of dengue viruses imported into Taiwan during 2011-2016

A total of 1,596 laboratory-confirmed imported dengue cases were identified in Taiwan during 2011–2016. Most of the imported cases arrived from Southeast Asia as well as the Indian subcontinent, the Pacific region, Latin America, Australia and Africa. Phylogenetic analyses of the complete envelope protein gene sequences from 784 imported dengue virus (DENV) isolates were conducted, and the results suggest that the DENV-1 genotype I and DENV-2 Cosmopolitan genotype comprise the predominant serotype/genotype of DENV strains circulating in Southeast Asia. The DENV-1 genotype III, DENV-3 genotype III and DENV-4 genotype I and II strains were found to be newly emerging in several Southeast Asian countries. Our results also showed that geographical restrictions of DENV-1 genotype I, DENV-1 genotype III and DENV-2 Cosmopolitan genotype are becoming blurred, indicating the extensive introductions and continuous expansions of DENV strains between nations in Southeast Asia. In this study, we present the geographic distribution and dynamic transmission of DENV strains circulating in Southeast Asian countries. In addition, we demonstrated local dengue epidemics caused by several imported DENV strains in Taiwan during 2011–2016.

Dengue is the most prevalent mosquito-borne viral disease in the world. The expansion of dengue viruses to different parts of the world has been accelerated by the increase in worldwide travel and trade. In this study, we present the results of a laboratory-based dengue surveillance in Taiwan during 2011–2016. A total of 1,596 laboratory-confirmed imported dengue cases were identified. The travelers were infected in 29 countries in Southeast Asia, the Indian subcontinent, the Pacific region, Latin America, Australia and Africa. Phylogenetic analyses of the envelope gene sequences of 784 imported dengue virus isolates suggest that the DENV-1 genotype I and DENV-2 Cosmopolitan genotype comprise the predominant serotype/genotype DENV strains circulating in Southeast Asia. Our results also showed that geographical restrictions of some of the DENV genotypes are becoming blurred, indicating the extensive introductions and continuous expansions of DENV strains between countries in Southeast Asia. In addition, we demonstrated dengue outbreaks in Taiwan caused by viruses imported from Asia and the Americas. The DENV envelope gene sequences from this study will contribute to a better understanding of the genetic evolution, dynamic transmission and global expansion of dengue viruses.

Dengue virus serotype distribution based on serological evidence in pediatric urban population in Indonesia

BACKGROUND

Dengue is a febrile illness transmitted by mosquitoes, causing disease across the tropical and sub-tropical world. Antibody prevalence data and serotype distributions describe population-level risk and inform public health decision-making.

METHODOLOGY/PRINCIPAL FINDINGS

In this cross-sectional study we used data from a pediatric dengue seroprevalence study to describe historical dengue serotype circulation, according to age and geographic location. A sub-sample of 780 dengue IgG-positive sera, collected from 30 sites across urban Indonesia in 2014, were tested by the plaque reduction neutralization test (PRNT) to measure the prevalence and concentration of serotype-specific neutralizing antibodies according to subject age and geography. PRNT results were obtained from 776 subjects with mean age of 9.6 years. 765 (98.6%) neutralized one or more dengue serotype at a threshold of >10 (1/dil). Multitypic profiles were observed in 50.9% of the samples; a proportion which increased to 63.1% in subjects aged 15-18 years. Amongst monotypic samples, the highest proportion was reactive against DENV-2, followed by DENV-1, and DENV-3, with some variation across the country. DENV-4 was the least common serotype. The highest anti-dengue antibody titers were recorded against DENV-2, and increased with age to a geometric mean of 516.5 [1/dil] in the oldest age group.

CONCLUSIONS/SIGNIFICANCE

We found that all four dengue serotypes have been widely circulating in most of urban Indonesia, and more than half of children had already been exposed to >1 dengue serotype, demonstrating intense transmission often associated with more severe clinical episodes. These data will help inform policymakers and highlight the importance of dengue surveillance, prevention and control.

Isolation and complete genome analysis of neurotropic dengue virus serotype 3 from the cerebrospinal fluid of an encephalitis patient

Although neurological manifestations associated with dengue viruses (DENV) infection have been reported, there is very limited information on the genetic characteristics of neurotropic DENV. Here we describe the isolation and complete genome analysis of DENV serotype 3 (DENV-3) from cerebrospinal fluid of an encephalitis paediatric patient in Jakarta, Indonesia. Next-generation sequencing was employed to deduce the complete genome of the neurotropic DENV-3 isolate. Based on complete genome analysis, two unique and nine uncommon amino acid changes in the protein coding region were observed in the virus. A phylogenetic tree and molecular clock analysis revealed that the neurotropic virus was a member of Sumatran-Javan clade of DENV-3 genotype I and shared a common ancestor with other isolates from Jakarta around 1998. This is the first report of neurotropic DENV-3 complete genome analysis, providing detailed information on the genetic characteristics of this virus.

Dengue viruses (DENV) are viruses that can cause asymptomatic infection to life-threatening haemorrhagic fever disease. Although DENV are not classically known to infect and invade central nervous system (CNS) in human, numerous cases of DENV infection in the CNS have been reported with limited information about the characteristics of the infecting virus. Here, we report the isolation and first complete genome analysis of DENV serotype 3 (DENV-3) from cerebrospinal fluid of a patient diagnosed with dengue encephalitis in Jakarta, Indonesia. By using next-generation sequencing strategy, we recovered the complete genome of the virus isolate and identified unique amino acid changes not found in any other recovered DENV-3 strains. The virus was determined to be closely related to isolates from Jakarta, Indonesia, which have been circulating for almost four decades.

Molecular characterization of dengue viruses isolated from patients in Central Java, Indonesia

BACKGROUND

Dengue is hyper-endemic in Indonesia. Purwokerto city in Central Java province is routinely ravaged by the disease. Despite the endemicity of dengue in this city, there is still no data on the virological aspects of dengue in the city. We conducted a molecular surveillance study of the circulating dengue viruses (DENV) in Purwokerto city to gain information on the virus origin, serotype and genotype distribution, and phylogenetic characteristics of DENV.

METHODS

A cross-sectional dengue molecular surveillance study was conducted in Purwokerto. Sera were collected from dengue-suspected patients attending three hospitals in the city. Diagnosis was performed using dengue NS1 antigen and IgG/IgM antibodies detection. DENV serotyping was performed using Simplexa Dengue real-time RT-PCR. Sequencing was conducted to obtain full-length DENV Envelope (E) gene sequences, which were then used in phylogenetic and genotypic analyses. Patients' clinical and demographic data were collected and analyzed.

RESULTS

A total of 105 dengue-suspected patients' sera were collected, in which 80 (76.2%) were positive for IgM and/or IgG, and 57 (54.2%) were confirmed as dengue by NS1 antigen and/or DENV RNA detection using RT-PCR. Serotyping was successful for 47 isolates. All four serotypes circulated in the area with DENV-3 as the predominant serotype. Phylogenetic analyses grouped the isolates into Genotype I for DENV-1, Cosmopolitan genotype for DENV-2, and Genotype I and II for DENV-3 and -4, respectively. The analyses also revealed the close relatedness of Purwokerto isolates to other DENV strains from Indonesia and neighboring countries.

CONCLUSION

We reveal the molecular and virological characteristics of DENV in Purwokerto, Banyumas regency, Central Java. The genotype and phylogenetic analyses indicate the endemicity of the circulating DENV in the city. Our serotype and genotype data provide references for future dengue molecular epidemiology studies and disease management in the region.

Chikungunya Detection during Dengue Outbreak in Sumatra, Indonesia: Clinical Manifestations and Virological Profile

Chikungunya fever (CHIK) is an acute viral infection caused by infection with chikungunya virus (CHIKV). The disease affects people in areas where certain Aedes species mosquito vectors are present, especially in tropical and subtropical countries. Indonesia has witnessed CHIK disease since the early 1970s with sporadic outbreaks occurring throughout the year. The CHIK clinical manifestation, characterized by fever, headache, and joint pain, is similar to that of dengue (DEN) disease. During a molecular study of a DEN outbreak in Jambi, Sumatra, in early 2015, DENV-negative samples were evaluated for evidence of CHIKV infection. Among 103 DENV-negative samples, eight samples were confirmed (7.8%) as positive for CHIKV by both molecular detection and virus isolation. The mean age of the CHIK patients was 21.3 ± 9.1 (range 11-35 years). The clinical manifestations of the CHIK patients were mild and mimicked DEN, with fever and headache as the main symptoms. Only three out of eight patients presented with classical joint pain. Sequencing of the envelope glycoprotein E1 gene and phylogenetic analysis identified all CHIKV isolates as belonging to the Asian genotype. Overall, our study confirms sustained endemic CHIKV transmission and the presence of multiple arboviruses circulating during a DEN outbreak in Indonesia. The co-circulation of arboviruses poses a public health threat and is likely to cause misdiagnosis and underreporting of CHIK in DEN-endemic areas such as Indonesia.

Phylogenetic and evolutionary analyses of dengue viruses isolated in Jakarta, Indonesia

Dengue has affected Indonesia for the last five decades and become a major health problem in many cities in the country. Jakarta, the capital of Indonesia, reports dengue cases annually, with several outbreaks documented. To gain information on the dynamic and evolutionary history of dengue virus (DENV) in Jakarta, we conducted phylogenetic and evolutionary analyses of DENV isolated in 2009. Three hundred thirty-three dengue-suspected patients were recruited. Our data revealed that dengue predominantly affected young adults, and the majority of cases were due to secondary infection. A total of 171 virus isolates were successfully serotyped. All four DENV serotypes were circulating in the city, and DENV-1 was the predominant serotype. The DENV genotyping of 17 isolates revealed the presence of Genotypes I and IV in DENV-1, while DENV-2 isolates were grouped into the Cosmopolitan genotype. The grouping of isolates into Genotype I and II was seen for DENV-3 and DENV-4, respectively. Evolutionary analysis revealed the relatedness of Jakarta isolates with other isolates from other cities in Indonesia and isolates from imported cases in other countries. We revealed the endemicity of DENV and the role of Jakarta as the potential source of imported dengue cases in other countries. Our study provides genetic information regarding DENV from Jakarta, which will be useful for upstream applications, such as the study of DENV epidemiology and evolution and transmission dynamics.

Dengue in Bali: Clinical characteristics and genetic diversity of circulating dengue viruses

A high number of dengue cases are reported annually in Bali. Despite the endemicity, limited data on dengue is available for Bali localities. Molecular surveillance study was conducted to explore the clinical and virological characteristics of dengue patients in urban Denpasar and rural Gianyar areas in Bali during the peak season in 2015. A total of 205 adult dengue-suspected patients were recruited in a prospective cross-sectional study. Demographic and clinical information were obtained, and dengue screening was performed using NS1 and IgM/IgG ELISAs. Viral RNA was subsequently extracted from patients’ sera for serotyping using conventional RT-PCR and Simplexa Dengue real-time RT-PCR, followed by genotyping with sequencing method. We confirmed 161 patients as having dengue by NS1 and RT-PCR. Among 154 samples successfully serotyped, the DENV-3 was predominant, followed by DENV-1, DENV-2, and DENV-4. Serotype predominance was different between Denpasar and Gianyar. Genotyping results classify DENV-1 isolates into Genotype I and DENV-2 as Cosmopolitan Genotype. The classification grouped isolates into Genotype I and II for DENV-3 and DENV-4, respectively. Clinical parameters showed no relationship between infecting serotypes and severity. We observed the genetic diversity of circulating DENV isolates and their relatedness with historical data and importation to other countries. Our data highlights the role of this tourist destination as a potential source of dengue transmission in the region.

Dengue is the most significant mosquito-borne viral disease affecting humans. Up to one third of the world population is at risk of dengue virus (DENV) infection, transmitted through the bite of Aedes mosquitoes. Bali, a well-known international tourist destination, is regularly ravaged by dengue disease. This disease impacts the health of both local people and visitors thus imposing a heavy economic burden. Bali has a constant flow of travelers and labors that contribute to the spread of DENV infection. Detailed characterization of DENV from Bali is limited; most reports are from travel-acquired cases. Here, we study dengue clinical and virological aspects in local Balinese people. We presented the clinical spectrum of the disease and the virological characteristics, observing the circulation of genetically diverse endemic virus strains including strains which are closely related to imported viruses in neighboring countries. The circulation of a lineage of DENV-2 proposed to cause outbreak in the past is also identified. Our study provides data on the genetic of circulating DENV in Bali which are useful for further applications, such as to monitor the virus transmission and outbreak investigation in the region.

Epidemiological Characteristics and Risk Factors of Dengue Infection in Korean Travelers

Dengue viral infection has rapidly spread around the world in recent decades. In Korea, autochthonous cases of dengue fever have not been confirmed yet. However, imported dengue cases have been increased since 2001. The risk of developing severe dengue in Korean has been increased by the accumulation of past-infected persons with residual antibodies to dengue virus and the remarkable growth of traveling to endemic countries in Southeast Asia. Notably, most of imported dengue cases were identified from July to December, suggesting that traveling during rainy season of Southeast Asia is considered a risk factor for dengue infection. Analyzing national surveillance data from 2011 to 2015, males aged 20-29 years are considered as the highest risk group. But considering the age and gender distribution of travelers, age groups 10-49 except 20-29 years old males have similar risks for infection. To minimize a risk of dengue fever and severe dengue, travelers should consider regional and seasonal dengue situation. It is recommended to prevent from mosquito bites or to abstain from repetitive visit to endemic countries. In addition, more active surveillance system and monitoring the prevalence asymptomatic infection and virus serotypes are required to prevent severe dengue and indigenous dengue outbreak.