Case report: dengue fever associated acute macular neuroretinopathy

Dengue fever (DF), which is caused by the dengue virus (DENV) and transmitted through Aedes mosquitoes, is well recognized for its systemic manifestations, with its ocular involvement gaining recent attention. We present a case of a 41-year-old Taiwanese female who developed acute macular neuroretinopathy (AMN) following a DF diagnosis related to DENV-1, emphasizing the need for awareness of this complication. The patient, with a history of completely resolved optic neuritis (ON) and comorbidities, experienced blurred vision on day 10 after the onset of DF. The ophthalmic examination revealed macular edema, ellipsoid zone (EZ) infiltration, and choriocapillaris involvement. Despite pulse therapy with corticosteroids, visual disturbances persisted, highlighting the challenge of managing ocular complications. Ocular manifestations in DF include hemorrhages, inflammation, and vascular complications. DF-associated AMN, a rare presentation, poses challenges in diagnosis and treatment response evaluation. While most patients recover spontaneously, some face persistent visual impairment, especially with AMN. Our case emphasizes the importance of recognizing ocular complications in DF, necessitating a multidisciplinary approach for optimal management and further research to delineate treatment strategies and outcomes.

Phylogenetics, Epidemiology and Temporal Patterns of Dengue Virus in Araraquara, São Paulo State

Dengue virus (DENV) is a prominent arbovirus with global spread, causing approximately 390 million infections each year. In Brazil, yearly epidemics follow a well-documented pattern of serotype replacement every three to four years on average. Araraquara, located in the state of São Paulo, has faced significant impacts from DENV epidemics since the emergence of DENV-1 in 2010. The municipality then transitioned from low to moderate endemicity in less than 10 years. Yet, there remains an insufficient understanding of virus circulation dynamics, particularly concerning DENV-1, in the region, as well as the genetic characteristics of the virus. To address this, we sequenced 37 complete or partial DENV-1 genomes sampled from 2015 to 2022 in Araraquara. Then, using also Brazilian and worldwide DENV-1 sequences we reconstructed the evolutionary history of DENV-1 in Araraquara and estimated the time to the most recent common ancestor (tMRCA) for serotype 1, for genotype V and its main lineages. Within the last ten years, there have been at least three introductions of genotype V in Araraquara, distributed in two main lineages (L Ia and L Ib, and L II). The tMRCA for the first sampled lineage (2015/2016 epidemics) was approximately 15 years ago (in 2008). Crucially, our analysis challenges existing assumptions regarding the emergence time of the DENV-1 genotypes, suggesting that genotype V might have diverged more recently than previously described. The presence of the two lineages of genotype V in the municipality might have contributed to the extended persistence of DENV-1 in the region.

DENV-1 Titer Impacts Viral Blocking in wMel Aedes aegypti with Brazilian Genetic Background

Several countries have been using Wolbachia deployments to replace highly competent native Aedes aegypti populations with Wolbachia-carrying mosquitoes with lower susceptibility to arboviruses such as dengue, Zika, and chikungunya. In Rio de Janeiro, Wolbachia deployments started in 2015 and still present a moderate introgression with a modest reduction in dengue cases in humans (38%). Here, we evaluated the vector competence of wild-type and wMel-infected Ae. aegypti with a Brazilian genetic background to investigate whether virus leakage could contribute to the observed outcomes in Brazil. We collected the specimens in three areas of Rio de Janeiro with distinct frequencies of mosquitoes with wMel strain and two areas with wild Ae. aegypti. The mosquitoes were orally exposed to two titers of DENV-1 and the saliva of DENV-1-infected Ae. aegypti was microinjected into wMel-free mosquitoes to check their infectivity. When infected with the high DENV-1 titer, the presence of wMel did not avoid viral infection in mosquitoes' bodies and saliva but DENV-1-infected wMel mosquitoes produced lower viral loads than wMel-free mosquitoes. On the other hand, wMel mosquitoes infected with the low DENV-1 titer were less susceptible to virus infection than wMel-free mosquitoes, although once infected, wMel and wMel-free mosquitoes exhibited similar viral loads in the body and the saliva. Our results showed viral leakage in 60% of the saliva of wMel mosquitoes with Brazilian background; thus, sustained surveillance is imperative to monitor the presence of other circulating DENV-1 strains capable of overcoming the Wolbachia blocking phenotype, enabling timely implementation of action plans.

Dengue 1 outbreak in Rosso, northern Senegal, October 2021: entomologic investigations

Senegal has experienced periodic epidemics of dengue in urban areas with increased incidence in recent years. However, few data are available on the local ecology of the epidemic vectors. In October 2021, a dengue outbreak was reported in northern Senegal to the Institute Pasteur de Dakar. Entomologic investigations then were undertaken to identify the areas at risk of transmission and to identify the vector(s). Adult mosquitoes were collected indoors and outdoors at selected households, while containers with water were inspected for mosquito larvae. All the Aedes aegypti (L.) collected were tested for dengue virus NS1 protein using a rapid diagnostic test (RDT), and positive samples were confirmed by real-time RT-PCR. The qRT-PCR positive samples were subjected to whole genome sequencing using Nanopore technology. The majority of the larvae-positive containers (83.1%) were used for water storage. The Breteau and Container indices exceeded the WHO-recommended thresholds for the risk of dengue virus transmission except at 2 localities. Ae. aegypti, the only reputed dengue vector, was collected resting indoors as well as outdoors and biting during the day and night. The NS1 protein was detected in 22 mosquito pools, including one pool of females emerging from field-collected larvae. All NS1-positive results were confirmed by RT-PCR. Virus serotyping showed that the outbreak was caused by DENV-1. This study demonstrates the need for continuous control of adult and aquatic stages of Ae. aegypti to prevent future dengue epidemics in Senegal. RDTs appear to be a promising tool for dengue diagnostics and surveillance.

Dengue virus serotype did not contribute to clinical severity or mortality in Taiwan's largest dengue outbreak in 2015

BACKGROUND

Dengue virus serotype 2 (DENV-2) was the major serotype in the 2015 dengue outbreak in Taiwan, while DENV-1 and DENV-3 were dominant between 2005 and 2014. We aimed to investigate whether DENV-2 contributed to disease severity and mortality in the outbreak in Kaohsiung city, Taiwan.

METHODS

We collected serum samples from dengue patients to detect the presence of DENV and determine the serotypes by using quantitative reverse transcription-polymerase chain reaction. Our cohorts comprised 105 DENV-1-infected cases and 1,550 DENV-2-infected cases. Demographic data, DENV serotype, and comorbidities were covariates for univariate and multivariate analyses to explore the association with severity and mortality.

RESULTS

The results suggested that DENV-1 persisted and circulated, while DENV-2 was dominant during the dengue outbreak that occurred between September and December 2015. However, DENV-2 did not directly contribute to either severity or mortality. Aged patients and patients with diabetes mellitus (DM) or moderate to severe chronic kidney disease (CKD) had a higher risk of developing severe dengue. The mortality of dengue patients was related to a higher Charlson comorbidity index score and severe dengue. Among DENV-2-infected patients and older patients, preexisting anti-dengue IgG, DM, and moderate to severe CKD were associated with severe dengue. Moreover, female sex and severe dengue were associated with a significantly higher risk of death.

CONCLUSIONS

Our findings highlight the importance of timely serological testing in elderly patients to identify potential secondary infections and focus on the meticulous management of elderly patients with DM or moderate to severe CKD to reduce dengue-related death.

Comparative analysis of the susceptibility of Aedes aegypti and Japanese Aedes albopictus to all dengue virus serotypes

BACKGROUND

Dengue fever, caused by the dengue virus (DENV), is the most common viral infection transmitted by Aedes mosquitoes (mainly Ae. aegypti and Ae. albopictus) worldwide. Aedes aegypti is not currently established in Japan, and Ae. albopictus is the primary vector mosquito for DENV in the country, but knowledge of its viral susceptibility is limited. Therefore, we aimed to clarify the status of DENV susceptibility by comparing the infection and dissemination dynamics of Japanese Ae. albopictus to all known DENV serotypes with those of Ae. aegypti.

METHODS

After propagation of each DENV serotype in Vero cells, the culture supernatants were mixed with defibrinated rabbit blood and adenosine triphosphate, and the mixture was artificially blood-sucked by two colonies of Ae. albopictus from Japan and one colony of Ae. aegypti from a dengue-endemic country (Vietnam). After 14 days of sucking, the mosquito body was divided into two parts (thorax/abdomen and head/wings/legs) and total RNA was extracted from each sample. DENV RNA was detected in these extracted RNA samples using a quantitative RT-PCR method specific for each DENV serotype, and infection and dissemination rates were analyzed.

RESULTS

The Japanese Ae. albopictus colonies were susceptible to all DENV serotypes. Its infection and dissemination rates were significantly lower than those of Ae. aegypti. However, the number of DENV RNA copies in Ae. albopictus was almost not significantly different from that in Ae. aegypti. Furthermore, Japanese Ae. albopictus differed widely in their susceptibility to each DENV serotype.

CONCLUSIONS

In Japanese Ae. albopictus, once DENV overcame the midgut infection barrier, the efficiency of subsequent propagation and dissemination of the virus in the mosquito body was comparable to that of Ae. aegypti. Based on the results of this study and previous dengue outbreak trends, Ae. albopictus is predicted to be highly compatible with DENV-1, suggesting that this serotype poses a high risk for future epidemics in Japan.

DENV-1 genotype V linked to the 2022 dengue epidemic in Southern Brazil

Even though Brazil is a country where the dengue virus (DENV) is endemic, until recently, Southern states did not have significant viral circulation, such as Rio Grande do Sul (RS), and some municipalities were even considered dengue-free. During 2022, these places have shown a sharp increase in the incidence of the disease, apparently following a worldwide growth pattern. Therefore, in this study, we monitor and characterize the genetic diversity of DENV circulating in southern Brazil through next-generation sequencing during an outbreak in 2022. We generated 70 DENV-1 genome sequences, all characterized as genotype V, divided into two clade clusters in the L1 lineage. Furthermore, unique mutations have been described in each clade of L1 lineage. Our results are essential in managing outbreaks since these data provide important information during the emergence of DENV circulation in RS. Since the south of Brazil has a lower viral circulation when compared to other Brazilian states, RS still lacks data that can help in understanding the transmission, dissemination, and evolution of the dengue virus. Hence, genomic surveillance efforts are essential to increase the accuracy of preventive actions and to control viral dissemination.

Molecular Characterization of Dengue Virus Strains from the 2019-2020 Epidemic in Hanoi, Vietnam

Dengue virus (DENV), which has circulated in Vietnam for several decades, has multiple serotypes and genotypes. A 2019 dengue outbreak resulted in a larger number of cases than any other outbreak. We conducted a molecular characterization using samples collected in 2019-2020 from dengue patients in Hanoi and nearby cities located in northern Vietnam. The circulating serotypes were DENV-1 (25%, n = 22) and DENV-2 (73%, n = 64). Phylogenetic analyses revealed that all DENV-1 (n = 13) were genotype I and clustered to local strains circulating during the previous outbreak in the 2017, whereas DENV-2 consisted of two genotypes: Asian-I (n = 5), related to local strains from 2006-2022, and cosmopolitan (n = 18), the predominant genotype in this epidemic. The current cosmopolitan virus was identified as having an Asian-Pacific lineage. The virus was closely related to strains in other recent outbreaks in Southeast Asian countries and China. Multiple introductions occurred in 2016-2017, which were possibly from maritime Southeast Asia (Indonesia, Singapore, and Malaysia), mainland Southeast Asia (Cambodia and Thailand), or China, rather than from an expansion of localized Vietnamese cosmopolitan strains that were previously detected in the 2000s. We also analyzed the genetic relationship between Vietnam's cosmopolitan strain and recent global strains reported from Asia, Oceania, Africa, and South America. This analysis revealed that viruses of Asian-Pacific lineage are not restricted to Asia but have spread to Peru and Brazil in South America.

Dengue Exposure and Wolbachia wMel Strain Affects the Fertility of Quiescent Eggs of Aedes aegypti

(1) Background: The deployment of the bacterium Wolbachia to reduce arbovirus transmission is ongoing in several countries worldwide. When Wolbachia-carrying Aedes aegypti are released and established in the field, females may feed on dengue-infected hosts. The effects of simultaneous exposure on life-history traits of Ae. aegypti to Wolbachia wMel strain and dengue-1 virus DENV-1 remain unclear. (2) Methods: We monitored 4 groups (mosquitoes with either DENV-1 or Wolbachia, coinfected with DENV-1 and Wolbachia, as well as negative controls) to estimate Ae. aegypti survival, oviposition success, fecundity, collapsing and fertility of quiescent eggs for 12 weeks. (3) Results: Neither DENV-1 nor Wolbachia had a significant impact on mosquito survival nor on mosquito fecundity, although the last parameter showed a tendency to decrease with ageing. There was a significant decrease in oviposition success in individuals carrying Wolbachia. Wolbachia infection and storage time significantly increased egg collapse parameter on the egg viability assay, while DENV-1 had a slight protective effect on the first four weeks of storage. (4) Conclusions: Despite limitations, our results contribute to better understanding of the tripartite interaction of virus, bacteria and mosquito that may take place in field conditions and aid in guaranteeing the Wolbachia strategy success.

A Six Years (2010-2016) Longitudinal Survey of the Four Serotypes of Dengue Viruses in Lao PDR

Dengue fever is the most prevalent arthropod-borne viral infection of humans in tropical and subtropical countries. Since 1979, dengue has been reported to be endemic in the Lao People's Democratic Republic (PDR), as in many countries in Southeast Asia, with a complex circulation of the four dengue viruses' serotypes (DENV-1 to DENV-4). By sequencing the complete envelope protein, we explored a panel of samples from five Lao Provinces (Vientiane capital, Luangprabang, Bolikhamxay, Saravane, Attapeu) to enrich knowledge about the co-circulation of DENVs in Lao PDR between 2010 and 2016. Phylogenetic analyses highlighted the specific circulation of DENV-1 genotype I, DENV-2 genotype Asian I, DENV-4 genotype I and the co-circulation of DENV-3 genotype II and III. The continuous co-circulation of the four serotypes was underlined, with genotype or cluster shifts among DENV-3 and DENV-1. These data suggested the emergence or re-emergence of DENV strains associated with epidemic events, potentially linked to the exchanges within the territory and with neighboring countries. Indeed, the increasing local or regional connections favored the dissemination of new isolates or new clusters around the country. Since 2012, the surveillance and alert system created in Vientiane capital by the Institut Pasteur du Laos appears to be a strategic tool for monitoring the circulation of the four serotypes, especially in this endemic country, and allows for improving dengue epidemiological knowledge to anticipate epidemic events better.

Genomic Characterization of Dengue Virus Outbreak in 2022 from Pakistan

Pakistan, a dengue-endemic country, has encountered several outbreaks during the past decade. The current study aimed to explore the serotype and genomic diversity of dengue virus responsible for the 2022 outbreak in Pakistan. From August to October 2022, NS-1 positive blood samples (n = 343) were collected from dengue patients, among which, (85%; n = 293) were positive based on RT-PCR. In terms of gender and age, dengue infection was more prevalent in male patients (63%; n = 184), with more adults (21-30 years; n = 94) being infected. The serotyping results revealed DENV-2 to be the most predominant serotype (62%; n = 183), followed by DENV-1 (37%; n = 109) and DENV-3 (0.32%; n = 1). Moreover, a total of 10 samples (DENV-2; n = 8, DENV-1; n = 2) were subjected to whole-genome sequencing. Among these, four were collected in early 2022, and six were collected between August and October 2022. Phylogenetic analysis of DENV-2 sequenced samples (n = 8) revealed a monophyletic clade of cosmopolitan genotype IVA, which is closely related to sequences from China and Singapore 2018, and DENV-1 samples (n = 2) show genotype III, which is closely related to Pakistan isolates from 2019. We also reported the first whole genome sequence of a coinfection case (DENV1-DENV2) in Pakistan detected through a meta-genome approach. Thus, dengue virus dynamics reported in the current study warrant large-scale genomic surveillance to better respond to future outbreaks.

Analysis of a Dengue Virus Outbreak in Rosso, Senegal 2021

Senegal is hyperendemic for dengue. Since 2017, outbreaks have been noticed annually in many regions around the country, marked by the co-circulation of DENV1-3. On 8 October 2021, a Dengue virus outbreak in the Rosso health post (sentinel site of the syndromic surveillance network) located in the north of the country was notified to the WHO Collaborating Center for arboviruses and hemorrhagic fever viruses at Institut Pasteur de Dakar. A multidisciplinary team was then sent for epidemiological and virologic investigations. This study describes the results from investigations during an outbreak in Senegal using a rapid diagnostic test (RDT) for the combined detection of dengue virus non-structural protein 1 (NS1) and IgM/IgG. For confirmation, samples were also tested by real-time RT-PCR and IgM ELISA at the reference lab in Dakar. qRT-PCR positive samples were subjected to whole genome sequencing using nanopore technology. Virologic analysis scored 102 positives cases (RT-PCR, NS1 antigen detection and/or IgM) out of 173 enrolled patients; interestingly, virus serotyping showed that the outbreak was caused by the DENV-1, a serotype different from DENV-2 involved during the outbreak in Rosso three years earlier, indicating a serotype replacement. Nearly all field-tested NS1 positives samples were confirmed by qRT-PCR with a concordance of 92.3%. Whole genome sequencing and phylogenetic analysis of strains suggested a re-introduction in Rosso of a DENV-1 strain different to the one responsible for the outbreak in the Louga area five years before. Findings call for improved dengue virus surveillance in Senegal, with a wide deployment of DENV antigenic tests, which allow easy on-site diagnosis of suspected cases and early detection of outbreaks. This work highlights the need for continuous monitoring of circulating serotypes which is crucial for a better understanding of viral epidemiology around the country.

Using Background Sequencing Data to Anticipate DENV-1 Circulation in the Lao PDR

Since its first detection in 1979, dengue fever has been considered a major public health issue in the Lao People’s Democratic Republic (PDR). Dengue virus (DENV) serotype 1 was the cause of an epidemic in 2010–2011. Between 2012 and 2020, major outbreaks due successively to DENV-3, DENV-4 and recently DENV-2 have been recorded. However, DENV-1 still co-circulated in the country over this period. Here, we summarize epidemiological and molecular data of DENV-1 between 2016 and 2020 in the Lao PDR. Our data highlight the continuous circulation of DENV-1 in the country at levels ranging from 16% to 22% among serotyping tests. In addition, the phylogenetic analysis has revealed the circulation of DENV-1 genotype I at least since 2008 with a co-circulation of different clusters. Sequence data support independent DENV-1 introductions in the Lao PDR correlated with an active circulation of this serotype at the regional level in Southeast Asia. The maintenance of DENV-1 circulation over the last ten years supports a low level of immunity against this serotype within the Lao population. Thereby, the risk of a DENV-1 epidemic cannot be ruled out in the future, and this emphasizes the importance of maintaining an integrated surveillance approach to prevent major outbreaks.

Phylogenetic Analysis of the Dengue Virus Strains Causing the 2019 Dengue Fever Outbreak in Hainan, China

Dengue virus is an arthropod-borne pathogen that is transmitted to humans primarily by Aedes spp. mosquitos, causing the acute infectious disease, dengue fever (DF). Until 2019, no dengue outbreak had been reported in Hainan Province for over 20 years. However, in early September of 2019, an increasing number of infected cases appeared and the DF outbreak lasted for over one month in Haikou City, Hainan Province. In our study, we collected 97 plasma samples from DF patients at three hospitals, as well as 1585 mosquito larvae samples from puddles in different areas of Haikou. There were 49 (50.5%) plasma samples found to be strongly positive and 9 (9.3%) plasma samples were weakly positive against the NS1 antigen. We discovered DENV both in the patient’s plasma samples and mosquito larvae samples, and isolated the virus from C6/36 cells inoculated with the acute phase serum of patients. Phylogenetic analysis revealed that the new strains were the most closely related to the epidemic strain in the southern regions of China, belonging to lineage IV, genotype I, DENV-1. Compared to the seven closest strains from neighboring countries and provinces, a total of 18 amino acid mutations occurred in the coding sequences (CDS) of the new isolated strain, DENV1 HMU-HKU-2. Our data shows that dengue virus is re-emerged in Hainan, and pose new threats for public health. Thus regular molecular epidemiological surveillance is necessary for control and prevention of DENV transmission.

Phylogenetic and recombinant analyses of complete coding sequences of DENV-1 from field-caught mosquitoes in Thailand

Dengue diseases are a group of infectious diseases that have been widespread throughout the world for several decades. Dengue outbreaks have occurred in many parts of the world, including Southeast Asia. The outbreak and the severity of the diseases depend on many factors including dengue genotype. Data on the genetic variation of dengue virus is highly informative for dengue protection plans and vaccine development. In this study, we focused on the analyses of genetic variation and amino acid changes of the whole coding sequences in two dengue strains isolated from Aedes mosquitoes in Bangkok, Thailand, an endemic area. The strains were identified as belonging to dengue virus serotype 1 (DENV-1) genotype I, and have unique nucleotide sequences. In the recombinant analysis, these strains were identified as recombinants derived from Chinese counterparts for both the major (DENV-1 genotype I) and the minor (DENV-1 genotype IV) parental strains. The recombination event occurred within the prM and E genes. This corresponded with the result of multiple alignments where several amino acid residues between the recombination breakpoints in the strains were identical to those in DENV-1 genotype IV. Several of the amino acid substitutions also have changed the amino acid properties, which might affect viral infection and antigenicity. These results provide insight into the genetic variation of DENV in this endemic area, which might have been involved in the dengue outbreak and high numbers of dengue haemorrhagic fever and dengue shock syndrome cases in Thailand in 2015.

Little Evidence of Zika Virus Infection in Wild Long-Tailed Macaques, Peninsular Malaysia

We tested a sample of 234 wild long-tailed macaques (Macaca fascicularis) trapped in Peninsular Malaysia in 2009, 2010, and 2016 for Zika virus RNA and antibodies. None were positive for RNA, and only 1.3% were seropositive for neutralizing antibodies. Long-tailed macaques are unlikely to be reservoirs for Zika virus in Malaysia.

Dengue Virus in Traveler Returning to Japan from the Democratic Republic of the Congo, 2015

Dengue fever (DF) is a mosquito-borne disease and a significant global public health problem. Although a few serological surveys in the literature suggest endemic DF in many parts of Africa, DF cases in these countries are generally underreported because of the lack of diagnostic testing and systematic surveillance; thus, little is known about the phylogenetic profile of circulating strains. In April 2015, DF was diagnosed in a Japanese national returning from the Democratic Republic of the Congo (DRC). Dengue virus 1 (DENV-1) RNA was detected in the patient's serum sample using real-time reverse transcription PCR. Phylogenetic analysis of the E gene revealed that the detected DENV-1 strain was classified as genotype V and was closely related, with 100% nucleotide identity, to the strain causing the 2013 DF epidemic in Angola, which is located directly south of the DRC. This is the first report to characterize the circulating DENV strain in the DRC, and the findings indicate that the DENV-1 strain causing the 2013 DF epidemic in Angola was also circulating in the DRC in 2015.

Molecular Characterization of Dengue E/NS1 Junction Genotype 2 Isolated From Saudi Patients, Jeddah Province

BACKGROUND AND OBJECTIVE

Dengue is the most important arthropod-borne viral disease which caused by the four-dengue virus serotypes (1-4) and its incidence has grown dramatically around the world in the recent decades. This study was conducted to determine the molecular characterization of dengue virus genotypes spreading in Jeddah province.

METHODOLOGY

To distinguish dengue virus genotypes, serum samples from 13 infected patients were subjected to envelop and non-structural 1 (E/NS1) gene amplification and sequence analysis at the nucleotide and amino acid levels.

RESULTS

The present partial dengue virus phylogenetic analysis announced the domination of dengue virus 2 genotype among the current dengue virus samples circulating in Jeddah province. Dengue virus 2 current isolates were grouped in one branch and seemed to be more closely related to various strains isolated from Sri-Lanka, Australia and Singapore and confirmed by internucleotide distance average ranged +/-0.01. Interestingly, sequences analysis of amino acids confirmed substitution of 8 amino acid residue (Ser729Gua, Ser729Arg, Val762Gau, Val780phe, Val781Leu, Val781Ala, Glu858Asp and Gln873His) among the present isolates comparing with previous references strains isolated from different countries. Remarkably, one unique amino acid residue Ala741Val was verified in the 10 present isolates compared to the reference sequence previously isolated from Jeddah.

CONCLUSION

Notably, the present study demonstrated the sequencing analysis of the dengue virus 2-E/NS1 on both nucleotide and amino acid levels and confirmed its endogenously prevalence in Jeddah.

Genomic analysis of dengue virus serotype 1 (DENV-1) genotypes from Surabaya, Indonesia

Dengue has caused a significant public health impact globally. With the diverse genetic of the causative viruses, analysis of dengue virus (DENV) genomes is important to supplement epidemiological data with information that can be used to reconstruct the history of epidemics in time and space. We have reported the clinical and virological characteristics of dengue in Surabaya, Indonesia and revealed the presence of all four DENV serotypes and the predominance of DENV-1. The further classification of Surabaya DENV-1 into two different genotypes warrants in-depth genomic analysis to study the dynamics of both genotypes and their contribution to virus evolution, virus transmission, and disease. We performed full-length genome sequencing to nine isolates' representatives from DENV-1 Genotype I and Genotype IV. Phylogenetic and evolutionary analyses suggested the more recent introduction of Genotype I viruses compared to the more endemic Genotype IV. Comparative analysis of Surabaya DENV-1 genomes and other sequences available publicly revealed that the majority of the DENV-1 codons were under strong purifying selection, while seven codon sites identified to be under positive selection. We highlight a unique codon site under the positive pressure in the NS1 gene of DENV-1. Our results provide additional genomic data of DENV from Indonesia that may contribute to the better understanding of dengue disease dynamics.

Circulating Genotypes of Dengue-1 Virus in South West India, 2014-2015

Dengue is the most prevalent arboviral disease affecting humans, with tropical and subtropical regions having the highest risk of dengue virus infections. The clinical symptoms often range from mild fever to fever with hemorrhagic manifestations and shock. Since 2010, India has been witnessing a marked increase in the number of dengue virus serotype 1 (DENV-1) infections, apart from those of serotypes 2 (DENV-2) and 3 (DENV-3). The present study was undertaken to understand the circulating genotypes of DENV-1 in South West India, by sequencing the envelope gene of DENV-1 samples representative of the 2014-2015 time period. The extracted RNAs from dengue NS1 antigen ELISA-positive samples, archived at the APEX Referral Laboratory for Arboviruses (National Vector Borne Disease Control Programme, Manipal Centre for Virus Research), were used for the study. The currently circulating genotypes of DENV-1 identified from the study area belong to genotypes V and I. Multicentric laboratory-based studies analyzing the envelope gene of all dengue serotypes are required from endemic countries like India.

Evolutionary history and spatiotemporal dynamics of DENV-1 genotype V in the Americas

The genotype V has been the most prevalent dengue virus type 1 (DENV-1) clade circulating in the Americas over the last 40years. In this study, we investigate the spatiotemporal pattern of emergence and dissemination of DENV-1 lineages in the continent. We applied phylogenetic and phylogeographic approaches to a comprehensive data set of 836 DENV-1 E gene sequences of the genotype V isolated from 46 different countries around the world over a period of 50years (1962 to 2014). Our study reveals that genetic diversity of DENV-1 genotype V in the Americas resulted from two independent introductions of this genotype from India. The first genotype V strain was most probably introduced into the Lesser Antilles at around the early 1970s and this Caribbean region becomes the source population of several DENV-1 lineages that spread in the Americas during the 1970s and 1980s. Most of those lineages appear to become extinct during the 1990s, except one that persisted in Venezuela and later spread to other American countries, dominating the DENV-1 epidemics in the region from the early 2000s onwards. The second genotype V strain of Indian origin was also most probably introduced into the Lesser Antilles at around the early 1980s. This lineage remained almost undetected for nearly 15years, until it was introduced in Northern Brazil around the middle 1990s and later spread to other country regions. These results demonstrate that different geographic regions have played a role in maintaining and spreading the DENV-1 genotype V in the Americas over time. DENV-1 genotype V lineages have originated, spread and died out in the Americas with very different dynamics and the phenomenon of lineage replacement across successive DENV-1 epidemic outbreaks was a common characteristic in most American countries.

The epidemiological characteristics and genetic diversity of dengue virus during the third largest historical outbreak of dengue in Guangdong, China, in 2014

OBJECTIVES

The third largest historical outbreak of dengue occurred during July to December 2014, in 20 of 21 cities of Guangdong, China. The epidemiological and molecular characteristics of the introduction, expansion and phylogeny of the DENV isolates involved in this outbreak were investigated.

METHODS

A combination analyses of epidemiological characteristics and genetic diversity of dengue virus was performed in this study.

RESULTS

In total, 45,236 cases and 6 fatalities were reported. Unemployed individuals, retirees and retailers were the most affected populations. A total of 6024 cases were verified to have DENV infections by nucleic acid detection, of which 5947, 74 and 3 were confirmed to have DENV-1, -2, and -3 infections, respectively. Phylogenetic analyses of DENV-1 isolates were assigned into three genotypes (I, IV, and V). Genotype V was the predominant genotype that likely originated from Singapore. The DENV-2 isolates were assigned to the Cosmopolitan and Asian I genotypes. A unique DENV-3 isolate (genotype III) shared high similarity with isolates obtained from Guangdong in 2013.

CONCLUSIONS

A combination analyses demonstrated the multiple geographical origins of this outbreak, and highlight the importance of early detection, the case management and vector surveillance for preventing further dengue epidemics in Guangdong.

Insights of the genetic diversity of DENV-1 detected in Brazil in 25 years: Analysis of the envelope domain III allows lineages characterization

Dengue virus type 1 (DENV-1) was first isolated in Brazil in 1986 in the state of Rio de Janeiro (RJ) and during 25years, this serotype emerged and re-emerged causing explosive epidemics in the country. Here, we aimed to present the phylogeny and molecular characterization based on the envelope gene (E) of DENV-1 (n=48) isolated during epidemics occurred from 1986 to 2011. Six full coding region genomes of DENV-1 were fully sequenced and possible genomic recombination events were analyzed. The results showed that the Brazilian DENV-1 isolates analyzed belong to genotype V (Americas/Africa), but grouping into distinct clades. Three groups were identified, one dating from 1986 to 2002 (lineage 1a), a second group isolated from 2009 to 2011 and a representative strain isolated in 2002 (lineage 2), and a group of strains isolated from 2010 to 2011 (lineage 1b). The lineages 1a and 1b were more closely related to the American strains, while lineage 2 to the Asian strains. Amino acids (aa) substitutions were observed in the domains I and III of the E protein and were associated to the lineages segregation. A substitution on E297 differentiated the lineage 1a from the lineages 1b and 2. Substitutions on E338, E394 (domain III), E428 and E436 (stem region) differentiated lineages 1a, 1b and 2. With the exception of the C gene, all the others genes analyzed allowed the DENV-1 classification into the distinct genotypes. Interestingly, the E gene's domain III and stem regions alone were able to characterize the distinct lineages, as observed by the analysis of the entire E gene and the complete coding region. No recombinant events were detected, but a strain belonging to lineage 1a was closely related to a known recombinant strain (AF513110/BR/2001).

Global phylogeography of Dengue type 1 and 2 viruses reveals the role of India

Patterns in virus dispersal and epidemiology of viral diseases can be revealed by phylogeographic studies. Currently knowledge about phylogeography of Dengue virus (DENV) Types 1 and 2 is limited. We carried out the phylogeographic analyses for DENV-1 and DENV-2, by the Bayesian Markov Chain Monte Carlo (MCMC) approach, with emphasis on Indian isolates in relation to the global evolutionary dynamics of the viruses. More than 250 E-gene sequences of each virus, available in GenBank, were used for the analyses. The study was focused on understanding the most likely geographical origin for the major genotypes and sub-lineages of DENV-1/DENV-2 and also the possible pathways in the dispersal of the virus. The results showed that for DENV-1, Southeast Asia was the most likely geographical origin and India was determined to be the ancestral location of the Cosmopolitan genotype circulating in India, Sri Lanka, West and East Africa, Caribbean region, East and Southeast Asia. For DENV-2, the ancestral source could not be precisely inferred. Further, in spite of the earliest isolate from Trinidad-1953 of the American genotype, it was depicted that India may have been the probable ancestor of this genotype. India was also determined to be the ancestral location of a subgroup of the Cosmopolitan genotype. It was noted that DENV-1 and DENV-2 were introduced into India during 1940s and 1910s respectively. Subsequently, dispersal of both the viruses between India and different regions including West, East and Central Africa, Southeast and East Asia and Caribbean was inferred. Overall, the current study provides insight into the spatial as well as temporal dynamics of dengue virus serotypes 1 and 2.

Genetic relatedness of dengue viruses in Key West, Florida, USA, 2009-2010

Sequencing of dengue virus type 1 (DENV-1) strains isolated in Key West/Monroe County, Florida, indicate endemic transmission for >2 years of a distinct and predominant sublineage of the American-African genotype. DENV-1 strains isolated elsewhere in Florida grouped within a separate Central American lineage. Findings indicate endemic transmission of DENV into the continental United States.

New vaccines for neglected parasitic diseases and dengue

Neglected tropical diseases (NTDs) are a significant source of morbidity and socioeconomic burden among the world's poor. Virtually all of the 2.4 billion people who live on less than $2 per d, more than a third of the world's population, are at risk for these debilitating NTDs. Although chemotherapeutic measures exist for many of these pathogens, they are not sustainable countermeasures on their own because of rates of reinfection, risk of drug resistance, and inconsistent maintenance of drug treatment programs. Preventative and therapeutic NTD vaccines are needed as long-term solutions. Because there is no market in the for-profit sector of vaccine development for these pathogens, much of the effort to develop vaccines is driven by nonprofit entities, mostly through product development partnerships. This review describes the progress of vaccines under development for many of the NTDs, with a specific focus on those about to enter or that are currently in human clinical trials. Specifically, we report on the progress on dengue, hookworm, leishmaniasis, schistosomiasis, Chagas disease, and onchocerciasis vaccines. These products will be some of the first with specific objectives to aid the world's poorest populations.