Dengue viremia titer, antibody response pattern, and virus serotype correlate with disease severity

TAK-003: development of a tetravalent dengue vaccine

INTRODUCTION

Dengue incidence has increased over the past few decades. One tetravalent dengue vaccine based on a yellow fever backbone has been approved, but due to increased risk of severe disease in dengue-naïve recipients, its use is limited to individuals with prior dengue exposure.

AREAS COVERED

We summarize the clinical development of TAK-003, a tetravalent dengue vaccine based on a live-attenuated DENV-2 backbone. We discuss vaccine development and preclinical and clinical work leading to a commercially available formulation. TAK-003 is approved in several countries and the WHO-SAGE recommend TAK-003 to be considered for public programs in high transmission areas for individuals aged 6-16 years. Finally, we discuss the potential role of TAK-003 as part of an integrated multimodal strategy for dengue prevention.

EXPERT OPINION

TAK-003 has been assessed in a comprehensive clinical development program; demonstrating sustained efficacy and safety against all four serotypes in baseline seropositive individuals, and against DENV-1 and DENV-2 in seronegative individuals, and has been well tolerated. Effectiveness in a real world setting and safety will be monitored in ongoing and future studies, particularly for DENV-3 and DENV-4, together with the impact of a booster dose. Overall, TAK-003 shows promise as a new tool for dengue prevention.

Multivalent administration of dengue E dimers on liposomes elicits type-specific neutralizing responses without immune interference

The four serotypes of dengue virus (DENV1-4) are a major health concern putting 50% of the global population at risk of infection. Crucially, DENV vaccines must be tetravalent to provide protection against all four serotypes because immunity to only one serotype can enhance infections caused by heterologous serotypes. Uneven replication of live-attenuated viruses in tetravalent vaccines can lead to disease enhancement instead of protection. Subunit vaccines are a promising alternative as the vaccine components are not dependent on viral replication and antigen doses can be controlled to achieve a balanced response. Here, we show that a tetravalent subunit vaccine of dengue envelope (E) proteins computationally stabilized to form native-like dimers elicits type-specific neutralizing antibodies in mice against all four serotypes. The immune response was enhanced by displaying the E dimers on liposomes embedded with adjuvant, and no interference was detected between the four components.

Emergence of Oropouche Virus in Espírito Santo State, Brazil, 2024

Oropouche virus (OROV), historically endemic to the Amazon, had spread to nearly all Brazil states by 2024; Espírito Santo emerged as a transmission hotspot in the Atlantic Forest biome. We characterized the epidemiologic factors driving OROV spread in nonendemic southeast Brazil, analyzing environmental and agricultural conditions contributing to viral transmission. We tested samples from 29,080 suspected arbovirus-infected patients quantitative reverse transcription PCR for OROV and dengue, chikungunya, Zika, and Mayaro viruses. During March‒June 2024, the state had 339 confirmed OROV cases, demonstrating successful local transmission. Spatial analysis revealed that most cases clustered in municipalities with tropical climates and intensive cacao, robusta coffee, coconut, and pepper cultivation. Phylogenetic analysis identified the Espírito Santo OROV strains as part of the 2022-2024 Amazon lineage. The rapid spread of OROV outside the Amazon highlights its adaptive potential and public health threat, emphasizing the need for enhanced surveillance and targeted control measures.

Development of a rapid point-of-care dengue virus type 2 infection diagnostic assay using recombinase polymerase amplification and lateral flow device

Introduction

Dengue virus (DENV) is the most rapidly spreading arbovirus globally, with over half of the world's population at risk of infection. Early and rapid detection is crucial to ensure timely patient care, reduce healthcare burden, and prevent severe disease progression. However, conventional nucleic acid amplification techniques are often unsuitable for low-resource settings due to their equipment and procedural demands.

Methods

We evaluated a real-time reverse transcription recombinase polymerase amplification (RT-RPA) assay for the sensitive and specific detection of DENV serotype 2 (DENV2). The assay was tested using both Twista fluorometer and lateral flow detection (LFD) formats. Analytical sensitivity was determined by probit regression, while specificity was assessed against unrelated viruses and other flaviviruses. Clinical validation was performed using serum, cell culture, and FTA® card samples. Assay robustness was evaluated under varying temperatures and after freeze-thaw cycles.

Results

The RT-RPA assay reliably amplified DENV2 at concentrations as low as 50 copies per reaction, with LOD₉₅ estimated at 38.48 copies (Twista) and 50.37 copies (LFD). No cross-reactivity was observed with respiratory syncytial virus, influenza, rabbit herpes virus, West Nile virus, or other DENV serotypes (DENV1, DENV3, DENV4). The assay successfully detected multiple DENV2 strains and maintained performance across 33°C-40°C and after repeated freeze-thaw cycles. RNA extracted from FTA® cards was successfully amplified. Clinical validation confirmed accurate detection in serum and cell culture samples, while DENV3-positive blood samples tested negative, reinforcing specificity.

Discussion

The RT-RPA/LFD assay offers a rapid, sensitive, and specific tool for DENV2 detection, compatible with low-resource and field-based settings. Its simplicity, robustness, and portability make it a promising approach for point-of-care diagnostics and outbreak surveillance in endemic regions.

Operational challenges and lessons learned from conducting febrile surveillance in a long-term randomized dengue vaccine trial in Latin America and Asia-Pacific

BACKGROUND

In trials, dengue vaccine efficacy evaluation relies on participants presenting with febrile illness/clinically suspected dengue contacting the study site for sample collection and clinical assessment within a short timeframe. Here, we present key considerations to maintain high compliance with the febrile surveillance procedures in a trial that assessed TAK-003 efficacy.

METHODS

DEN-301 (NCT02747927) is a randomized phase 3 trial in children/adolescents from eight dengue-endemic countries in Latin America (LATAM) and Asia-Pacific (APAC). Febrile surveillance consisted of weekly contact with the participant to identify cases of fever (≥38 °C; two of three consecutive days). Blood samples were collected for molecular testing, preferably ≤5 days of fever onset, together with thorough clinical assessment by the investigators. The data are presented descriptively.

RESULTS

Of the 20,071 (LATAM, 11,080; APAC, 8991) participants who received TAK-003/placebo, 18,260 (91.0 %) completed 4.5 years of follow-up. The overall incidence of febrile illness was 30 (LATAM, 26.0; APAC, 35.1) cases per 100 person-years. The rate samples collected during the acute phase was 98.1 %. The overall rate of samples collected after 5 days of fever onset (missed/out-of-window) was 6 % (LATAM, 10 %; APAC, 2 %). A trend toward reduced missed/out-of-window samples was observed after implementing measures, such as transportation, engagement, and healthcare aid tailored per study site in 2017, which appeared to increase during the COVID-19 pandemic.

CONCLUSION

The design of the febrile surveillance protocol ensured high compliance in the trial. Maintaining engagement and access to healthcare beyond the protocol was important in improving febrile case evaluation ≤5 days of fever onset.

From Antibodies to Immunity: Assessing Correlates of Flavivirus Protection and Cross-Reactivity

Flaviviruses are arthropod-borne RNA viruses that can cause a wide range of human diseases, from mild symptoms to severe illness with multiorgan failure and death. Effective prevention of these diseases relies on identifying reliable vaccine targets, typically measured by correlates of protection (CoPs), which help indicate host immunity after vaccination. Current vaccines primarily focus on neutralizing antibodies (nAbs) against the viral envelope E protein, though emerging evidence suggests other potential targets may also be effective in disease prevention. Additionally, there is growing evidence of cross-protection between different flaviviruses when immunity to one virus is achieved, although this can be limited by antibody-dependent enhancement. This review examines the current understanding of flavivirus immunity, CoPs, and the potential for cross-protection in the context of existing vaccine strategies.

Dengue Viral Infection Induces Alteration of CD95 Expression in B Cell Subsets with Potential Involvement of Dengue Viral Non-Structural Protein 1

Little is known about the regulation of B cell subpopulations in association with programmed cell death during dengue virus (DENV) infection. Therefore, blood samples from dengue-infected patients and healthy donors were obtained for B cell subset characterization and the analysis of pro-apoptotic CD95 expression in these cell subsets. The results showed that the activated memory (AM) subset in the patients remained unchanged compared to the healthy donors. In contrast, tissue memory (TM) and antibody-secreting cells (ASCs) were notably increased, whereas naïve cells and resting memory (RM) cells were considerably decreased. Although the ASCs maintained comparably high levels of CD95 expression in both groups, significantly increased percentages of CD95-expressing cells in the other B cell subsets were found in the patients. When B cells from the healthy donors were treated with DENV non-structural protein 1 (NS1), the results showed that the NS1 protein at 2 µg/mL could induce CD95 expression and the exposure of phosphatidylserine on the cell membrane in most B cell subsets, except for the RM. This study demonstrates that DENV infection could induce CD95 expression in both activated and resting B cell subsets in all patients. The results also suggest a potential mechanism of apoptotic regulation in B cell subsets through the increased CD95 expression caused by the interaction between the B cells and the NS1 protein.

Impact of ADE and Dengue Vaccination with Screening on Cost and Disease Burden for Homoserotypic Dengue and Zika

The tetravalent dengue vaccine Dengvaxia® may prime dengue-seronegative vaccinees for antibody-dependent enhancement (ADE) of any subsequent dengue (in case of vaccine failure) or Zika infections. Many researchers associate ADE of such cases with more severe outcomes including death. This study uses a mathematical model of transmission dynamics that distinguishes ADE and non-ADE cases for each virus, to identify the potential impact of a dengue screening and vaccination campaign on the economic cost and disease burden of a dual dengue-Zika outbreak, under the hypothesis that severe outcomes are associated with ADE. Results indicate that when all dengue exposure is to a single serotype, in most cases vaccination increases both cost and burden because they are dominated by the high costs associated with complications from ADE Zika cases. However, if per-case ADE Zika costs are lower than estimated (a real possibility given the limited data available), by a factor ranging from 1 to 6 (for cost, except in Vietnam) or 8 (for burden), sufficiently high vaccination coverage can reduce total cost and burden substantially over a year. Analysis also identifies variations across countries, dengue serotypes, and timeframes of evaluation.

Pathogenesis and clinical management of arboviral diseases

Arboviral diseases are viral infections transmitted to humans through the bites of arthropods, such as mosquitoes, often causing a variety of pathologies associated with high levels of morbidity and mortality. Over the past decades, these infections have proven to be a significant challenge to health systems worldwide, particularly following the considerable geographic expansion of the dengue virus (DENV) and its most recent outbreak in Latin America as well as the difficult-to-control outbreaks of yellow fever virus (YFV), chikungunya virus (CHIKV), and Zika virus (ZIKV), leaving behind a substantial portion of the population with complications related to these infections. Currently, the world is experiencing a period of intense globalization, which, combined with global warming, directly contributes to wider dissemination of arbovirus vectors across the globe. Consequently, all continents remain on high alert for potential new outbreaks. Thus, this review aims to provide a comprehensive understanding of the pathogenesis of the four main arboviruses today (DENV, ZIKV, YFV, and CHIKV) discussing their viral characteristics, immune responses, and mechanisms of viral evasion, as well as important clinical aspects for patient management. This includes associated symptoms, laboratory tests, treatments, existing or developing vaccines and the main associated complications, thus integrating a broad historical, scientific and clinical approach.

Development and Validation of a Combined RT-LAMP Assay for the Rapid and Sensitive Detection of Dengue Virus in Clinical Samples from Colombia

Background: Dengue virus (DENV) infection is a significant public health concern in several tropical and subtropical regions, where early and rapid detection is crucial for effective patient management and controlling the spread of the disease. Particularly in resource-limited, rural healthcare settings where dengue is endemic, there exists a need for diagnostic methods that are both easy to perform and highly sensitive. Objective: This study focuses on the development and validation of a single-tube reverse transcription loop-mediated isothermal amplification termed TURN-RT-loop-mediated isothermal amplification (LAMP) for the detection of DENV. Methodology: The TURN-RT-LAMP assay designed in this study combines two sets of primers targeting the 5'- and 3'-UTR of DENV, with the aim to increase the sensitivity of detection. Results: Clinical validation of the TURN-RT-LAMP assay using samples collected from febrile individuals with a serological or antigenic diagnosis revealed a sensitivity of >96%. The performance of this assay was statistically compared with that of the standard diagnostic method, quantitative reverse transcription-polymerase chain reaction. Conclusions: The results support the potential of RT-LAMP as a rapid, sensitive, and specific tool for the diagnosis and surveillance of dengue, particularly suitable for field use in low-resource settings.

Estimating per-infection cost and burden for dengue and Zika as a function of antibody-dependent enhancement

The complex immune interactions produced by the tetravalent dengue vaccine Dengvaxia have foregrounded the important role of antibody-dependent enhancement (ADE) in dengue infection. Some evidence exists that ADE may extend beyond the four dengue serotypes to Zika, a closely related flavivirus transmitted by the same mosquito species as dengue, and may also account for the increased severity of some cases. Estimates of the public health impact of dengue vaccination may then need to include its effects on the transmission of Zika in addition to dengue. This study gathers primary references to build estimates of per-case economic cost and disease burden for dengue and Zika infection with and without ADE in the ten countries where clinical trials were held for Dengvaxia, under the hypothesis that severe outcomes are associated with ADE of disease. From these estimates, per-infection weighted averages are developed (without assumptions on transmission dynamics or case totals) which will facilitate population-level estimates of the potential impact of dengue vaccination on a dual outbreak using mathematical modeling. Results estimate that ADE amplifies the per-case toll of dengue by a factor of 2-16 but increases that of a Zika case by more than two orders of magnitude due to the greater risk of severe consequences. As expected, dengue vaccination affects per-infection dengue toll much more when high prior dengue seropositivity involves a different serotype than the one(s) circulating, but that same high dengue seropositivity makes vaccination exacerbate Zika toll less.

Overview of dengue diagnostic limitations and potential strategies for improvement

INTRODUCTION

Dengue is a viral infection caused by any one of the four related dengue virus (DENV) serotypes, 1-4. DENV is a single-stranded RNA virus belonging to the genus Flavivirus. Dengue can cause a range of symptoms, from mild to severe life-threatening illness. Currently, treatment for DENV is limited to supportive care, with better outcomes achieved through early diagnosis. The WHO has suggested that dengue mortality can be reduced to nearly zero by implementing appropriate clinical management strategies, such as early laboratory diagnosis. This calls for diagnostic approaches that combine high sensitivity and specificity, while also being suitable for point-of-care testing (POCT) in remote locations with minimal staff training and low testing costs.

CONTENT

In this paper, we outline the limitations of existing confirmatory dengue diagnostic methods, such as ELISA and RT-PCR, which are time-consuming, expensive, and require skilled personnel. We also highlight alternative strategies to overcome these challenges. Additionally, the paper emphasizes the growing clinical demand for diagnosing severe dengue to reduce the risk of death, which must be addressed by next-generation dengue diagnostic approaches.

SUMMARY

We propose the adoption of alternative strategies, such as fluorescence immunoassay (FIA) and chemiluminescence immunoassay (CLIA), which have the potential to overcome the limitations of existing dengue diagnostic methods.

OUTLOOK

Improvements in dengue diagnosis, with a specific focus on identifying severe dengue in POCT setting, can help achieve the goal of zero deaths from dengue.

Utility of VIDAS® Dengue Diagnostic Assays to Differentiate Primary and Secondary Dengue Infection: A Cross-Sectional Study in a Military Hospital from Colombia

This study aimed to assess the diagnostic utility of VIDAS® DENGUE NS1 Ag and anti-DENV IgM and IgG assays in parallel for an early and accurate diagnosis and classification of dengue virus (DENV) infection. For this retrospective cross-sectional study, 190 patients with suspected dengue were tested using VIDAS® NS1, IgM, and IgG assays, requested in parallel, regardless of symptom onset timing, and classified into primary and secondary infections. Results were analyzed to determine diagnostic accuracy and correlation with disease severity. Parallel testing effectively differentiated between primary and secondary DENV infection. Secondary dengue cases with warning signs showed significantly elevated IgG levels (p = 0.026). Notably, NS1-negative (possible secondary cases) had higher IgM and IgG levels than NS1-positive cases (p < 0.01), suggesting that NS1 negativity might indicate an amplified immune response. In conclusion, VIDAS® Dengue diagnostic assays not only enhance the diagnostic accuracy of dengue infection but also offer valuable insights into serological patterns, especially in secondary cases. These assays could be used not only to confirm diagnosis but also to stratify patients by risk, particularly in cases of secondary dengue, where IgG levels might indicate a higher risk for severe outcomes.

Enhancing surveillance for dengue fever in Oyo State, Nigeria - a one health approach

BACKGROUND

Dengue fever (DF) poses a growing global threat, necessitating a comprehensive one-health approach to address its complex interplay between human, animal, and environmental factors. In Oyo State, Nigeria, the true burden of DF remains unknown due to underdiagnosis and misdiagnosis as malaria, exacerbated by poor health-seeking behavior, weak surveillance systems, and inadequate health infrastructure. Adopting a one-health approach is crucial to understanding the dynamics of DF transmission.

METHODS

A cross-sectional study was conducted from January 2022 to April 2023 in 10 high-risk LGAs of Oyo State. It involved screening DENV in 289 febrile human blood samples and 1,015 Aedes species mosquitoes. Viral RNA from human and mosquito specimens was extracted and analyzed using RT-qPCR. A one-step lateral flow immunoassay cassette test kit detected DENV-specific IgM and IgG in humans. DENV IgM-positive participants were screened for Lassa Virus (LASV) to rule out coinfection due to an outbreak of Lassa fever. Mosquitoes recovered were morphologically identified and classified using appropriate taxonomical keys. Meteorological data was obtained from the Nigeria Meteorological Agency. Data was abridged as proportions and correlation analysis was performed.

RESULT

The overall seroprevalence of DENV was 128/289 (44.2%) with 19/289 (6.6%) and 109/289 (37.7%) being IgM and IgG positive respectively. DENV was detected all year round with more cases in the rainy season. LASV and DENV coinfection were detected in a participant. DENV RT-qPCR analysis in febrile patients and mosquitoes was negative. There was a high abundance of Aedes aegypti (79.5%) in all the locations surveyed with Aedes albopictus (12.3%) detected in Ido LGA and Ibadan South-East LGA and Aedes simpsoni (9.1%) in Iwajowa LGA. DF shows moderate to strong positive correlations with Aedes mosquito population, humidity, and rainfall (r = 0.419-0.61, p < 0.05), and a negative correlation with temperature (r =-0.465, p < 0.05).

CONCLUSION

The study reveals a significant burden of DENV in Oyo State. The presence of both IgM and IgG antibodies suggests past exposure and possible recent circulation of the virus. The co-detection of LASV and DENV in one participant highlights the likely potential for co-infection. Although DENV was not detected in febrile patients and mosquitoes through RT-qPCR, the high abundance of Aedes species underscores the risk of transmission. These findings emphasize the need for enhanced surveillance systems, strengthened laboratory services, targeted vector control, and increased awareness.

Dengue severity by serotype and immune status in 19 years of pediatric clinical studies in Nicaragua

BACKGROUND

Dengue virus, a major global health threat, consists of four serotypes (DENV1-4) that cause a range of clinical manifestations from mild to severe and potentially fatal disease.

METHODS

This study, based on 19 years of data from the Pediatric Dengue Cohort Study and Pediatric Dengue Hospital-based Study in Managua, Nicaragua, investigates the relationship of serotype and immune status with dengue severity. Dengue cases were confirmed by molecular, serological, and/or virological methods, and study participants 6 months to 17 years old were followed during their hospital stay or as ambulatory patients.

RESULTS

We enrolled a total of 15,833 participants, of whom 3,308 (21%) were positive for DENV infection. Of 2,644 cases with serotype result by RT-PCR, 559 corresponded to DENV1, 1,002 to DENV2, 760 to DENV3 and 323 to DENV4. Severe disease was more prevalent among secondary DENV2 and DENV4 cases, while similar disease severity was observed in both primary and secondary DENV1 and DENV3 cases. According to the 1997 World Health Organization (WHO) severity classification, both DENV2 and DENV3 caused a higher proportion of severe disease compared to other serotypes, whereas DENV3 caused the greatest percentage of severity according to the WHO-2009 classification. DENV2 was associated with increased odds of pleural effusion and low platelet count, while DENV3 was associated with both hypotensive and compensated shock.

CONCLUSIONS

These findings demonstrate differences in dengue severity by serotype and immune status and emphasize the critical need for a dengue vaccine with balanced effectiveness against all four serotypes, particularly as existing vaccines show variable efficacy by serotype and serostatus.

Localized Inflammation in Dengue Vaccine-Induced Skin Rash Is Not Associated with Continuous Presence of Dengue Virus Genome

Vaccination with the tetravalent live-attenuated dengue virus (DENV) vaccines TV003 and TV005 causes a mild, relatively localized erythematous maculopapular skin rash in most dengue-naïve vaccinees. Human challenge model DENV strains, DENV2Δ30 and DENV3Δ30, trigger a confluent skin rash over most of the body in most unvaccinated participants. To determine the etiology of these rashes, we performed in situ hybridization for DENV genome and assessed cellular infiltration by H&E staining in skin biopsies from humans infected with live-attenuated dengue vaccine DENV2Δ30 or DENV3Δ30 challenge strains. Sixty-three biopsies from 40 participants were included in the study, of which 43 biopsies from 32 patients contained intact RNA. Of these, 1 sample taken from a nonerythematous site from a DENV2Δ30-infected participant experiencing a rash was positive for DENV2 genome. Incidence and severity of lymphocytic infiltration were highest in rash biopsy samples than in those from noninvolved areas in participants experiencing a rash or from those taken from participants not experiencing a rash. These results indicate that the rash associated with infection with live-attenuated dengue vaccines or challenge strains is predominantly lymphocyte-driven perivascular dermal inflammation without local concomitant active viral replication.

Whole-blood model reveals granulocytes as key sites of dengue virus propagation, expanding understanding of disease pathogenesis

Dengue virus (DENV) infection poses a significant global health threat, yet our understanding of its immunopathogenesis remains incomplete due to limitations of existing models. Here, we establish an in vitro whole-blood model using hirudin, an anticoagulant that preserves complement activity and cellular interactions, to study DENV infection. Our model reveals the susceptibility of all major leukocyte populations to DENV infection, with monocytes and granulocytes demonstrating high permissiveness and production of infectious virus progeny. Notably, granulocytes emerge as previously unrecognized targets of DENV infection, highlighting the importance of studying viral tropism within a physiologically relevant context. We also observed efficient DENV binding to B cells, but limited production of infectious virus, suggesting a potential role in viral sequestration or immune dysregulation. Interestingly, both NK and T cells, while less permissive, were also found to be susceptible to DENV infection. Our ex vivo analysis of whole blood from DENV-infected patients confirms the susceptibility of granulocytes, monocytes, B cells, natural killer cells, and T cells to infection, further validating the clinical relevance of our model. Additionally, we observed dynamic changes in circulating blood cell populations during acute dengue, potentially reflecting both direct virus-mediated effects and immune responses. This whole-blood model offers a valuable tool for investigating the complex interplay between DENV and host factors, facilitating a deeper understanding of dengue pathogenesis and ultimately contributing to the development of novel therapeutic strategies.IMPORTANCEDengue virus (DENV) infection is a significant global health threat, with increasing incidence in endemic regions and expanding geographic range due to factors like global warming. Current models for studying DENV pathogenesis often lack the complexity of the human immune system, hindering the development of effective therapies and vaccines. To address this, we have established the first in vitro whole-blood model using hirudin, preserving critical immune components and cellular interactions. This model reveals granulocytes as previously unrecognized targets of productive DENV infection, challenging existing paradigms of viral tropism. Our ex vivo analysis of patient blood samples confirms the clinical relevance of this finding and validates our model's utility. This unique model offers a powerful platform for future studies to dissect the complex interactions between DENV and the host immune system, including the roles of different leukocyte populations, ultimately informing the development of novel therapeutic strategies to combat this devastating disease.

In-host modeling of dengue virus and non-structural protein 1 and the effects of ivermectin in patients with acute dengue fever

The increased incidence of dengue poses a substantially global public health challenge. There are no approved antiviral drugs to treat dengue infections. Ivermectin, an old anti-parasitic drug, had no effect on dengue viremia, but reduced the dengue non-structural protein 1 (NS1) in a clinical trial. This is potentially important, as NS1 may play a causal role in the pathogenesis of severe dengue. This study established an in-host model to characterize the plasma kinetics of dengue virus and NS1 with host immunity and evaluated the effects of ivermectin, using a population pharmacokinetic-pharmacodynamic (PK-PD) modeling approach, based on two studies in acute dengue fever: a placebo-controlled ivermectin study in 250 adult patients and an ivermectin PK-PD study in 24 pediatric patients. The proposed model described adequately the observed ivermectin pharmacokinetics, viral load, and NS1 data. Bodyweight was a significant covariate on ivermectin pharmacokinetics. We found that ivermectin reduced NS1 with an EC50 of 67.5 μg/mL. In silico simulations suggested that ivermectin should be dosed within 48 h after fever onset, and that a daily dosage of 800 μg/kg could achieve substantial NS1 reduction. The in-host dengue model is useful to assess the drug effect in antiviral drug development for dengue fever.

Emergence and increased epidemic potential of dengue variants with the NS5V357E mutation after consecutive years of transmission

Arboviruses can intensify epidemics by acquiring single nucleotide variants, leading to clade replacement and severe outbreaks. We investigated dengue virus serotype 2 evolution in consecutive outbreaks from 2001 to 2003 in Taiwan, coinciding with overwintering and increased epidemic severity. The virus evolved from the early-epidemic strain (Ia) to the late-epidemic strains (Ib and II), featuring three amino acid differences. The later strains demonstrated increased replication at lower temperatures, and the NS5V357E mutation significantly boosts virus replication and virulence, regardless of the other two mutations (ET46I and NS5I271T). Crucially, the late NS5V357E signature swiftly emerged after infecting mosquitos with the early Ia strain, through thoracic injection or by feeding on Ia-infected mice. Thus, we discover the molecular events involved in overwintering and increased disease severity between consecutive dengue outbreaks. This study enhances our understanding of dengue epidemiology, aiding in predicting and monitoring the emergence of dengue strains with increased epidemic potential.

Anti-dengue viral activity of Glycyrrhiza glabra roots in Vero cells

Despite being a global public health problem, there are no antiviral agents for dengue. Plants are the sources of most approved drugs and many phytochemicals have exhibited in vitro antiviral activity. We explored the antiviral potential of the aqueous extract of Glycyrrhiza glabra roots (GGaq) on dengue viruses. Plaque reduction antiviral assay for half maximal inhibitory concentrations (IC50) was done in Vero cells infected with dengue serotypes 1-4 and exposed to varying concentrations of GGaq. Half-maximal cytotoxic concentration (CC50) of the GGaq was 651.9 µg/mL. The IC50 of the four dengue serotypes (10-50 µg/mL) indicated moderate inhibition by GGaq. 98-100% inhibition of all dengue serotypes was seen with GGaq at the maximum nontoxic dose. Preparative thin layer chromatography of GGaq, isolated sub fractions E and F which had low to moderate antiviral activity (IC50 12.65-85.95 and IC50 13.14-69.27 respectively). They exhibited good therapeutic potential only for dengue serotype-4. Virus adsorption to cells was significantly inhibited by GG (50%) and sub fraction E (24.9%). Chloroquine diphosphate was used as the positive control in all assays. The aqueous extract of GG was non-toxic and had better antiviral activity than sub fractions E and F.

An update on the ocular manifestations of dengue

Dengue is the most common arboviral disease. It is typically spread by the bite of an infected female Aedes aegypti or Aedes albopictus mosquitoes. Dengue is endemic in subtropical and tropical regions, but its geographic reach keeps expanding. Ophthalmic manifestations of dengue are common and may present with a wide spectrum of ophthalmic findings. These may range from conjunctival petechiae, retinal hemorrhage, retinal vasculitis to panophthalmitis. Some of these may be vision threatening and may require urgent ophthalmic evaluation. The precise pathophysiologic mechanisms involved in dengue infection involve a complex interplay between host immune responses, virus, and host genes. There is no specific treatment for ocular dengue. Therefore, treatment is supportive. Despite the lack of proven efficacy, corticosteroids have been used in vision-threatening dengue-related ocular complications. Dengue must be considered in endemic areas, and a careful travel history needs to be elicited in nonendemic areas.

Immunologic Crosstalk and Host-Specific Immune Signature Associated with Dengue

In tropical and subtropical regions, dengue fever is a common febrile illness that is mostly spread by Aedes mosquitoes. Urban population migration, inadequate water storage facilities, and high mosquito density are features associated with this disease. The severity of the illness ranges from mild to deadly dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS), often with severe cases causing profound shock from extensive plasma leakage, and may result in demise. The symptoms of the illness include headache, myalgia, retro-orbital pain, and hemorrhagic signs. There may also be an intermittent shift in blood vessel integrity and coagulation, but recovery is typically complete and rapid. In this review, we emphasize the immunological aspects of this illness. The intricate interactions among the virus, host genes, and host immune systems impact the pathophysiology of dengue. Postinfection antibody-dependent enhancement is prominent, which significantly influences the etiology and virulence of the disease. Whereas the severe form only manifests when the host immune system is actively working to eradicate the infection by secreting several inflammatory cytokines, chemokines, and lipid mediators, for example, early dengue virus infection (DVI) resulted in the production of Interleukin 2 (IL-2), IL-6, and later infection, IL-4, IL-5, and IL-10. Higher concentrations of interferons gamma (IFN-gamma), granulocyte-macrophage colony-stimulating factor (GM-CSF), macrophage migration inhibitory factor (MIF), IL-1, IL-2, IL-4, IL-6, IL-7, IL-10, IL-12, and IL-13 were found in DHF patients. These are significantly more prevalent in severe infections than in mild ones. Numerous immunopathogenic processes involving both virus and host variables influence the severity of dengue. There is growing evidence that a compromised immune system limits viral clearance and causes severe inflammation, which in turn causes dengue hemorrhagic fever and dengue shock syndrome. Furthermore, the capacity of DENV to infect a broad range of immune cells, such as macrophages, dendritic cells, mast cells, T and B cells, and monocytes, further dysregulates these cells' antiviral activities, leading to the spread of the virus. Even though a number of risk factors linked to the advancement of the disease have been suggested, further research and evaluation of novel technologies are necessary to understand the complicated etiology and develop reliable and effective vaccines to fight against this febrile illness.

An effective pan-serotype dengue vaccine and enhanced control strategies could help in reducing the severe dengue burden in Bangladesh-A perspective

Dengue is an important vector-borne disease occurring globally. Dengue virus (DENV) infection can result in a potentially life-threatening disease. To date, no DENV-specific antiviral treatment is available. Moreover, an equally effective pan-serotype dengue virus vaccine is not available. Recently, two DENV vaccines, Dengvaxia and Qdenga, were licensed for limited use. However, none of them have been approved in Bangladesh. DENV is transmitted by Aedes mosquitoes, and global warming caused by climate change favoring Aedes breeding plays an important role in increasing DENV infections in Bangladesh. Dengue is a serious public health concern in Bangladesh. In the year 2023, Bangladesh witnessed its largest dengue outbreak, with the highest number of dengue cases (n = 321,179) and dengue-related deaths (n = 1,705) in a single epidemic year. There is an increased risk of severe dengue in individuals with preexisting DENV-specific immunoglobulin G if the individuals become infected with different DENV serotypes. To date, vector control has remained the mainstay for controlling dengue; therefore, an immediate, strengthened, and effective vector control program is critical and should be regularly performed for controlling dengue outbreaks in Bangladesh. In addition, the use of DENV vaccine in curbing dengue epidemics in Bangladesh requires more consideration and judgment by the respective authority of Bangladesh. This review provides perspectives on the control and prevention of dengue outbreaks. We also discuss the challenges of DENV vaccine use to reduce dengue epidemics infection in Bangladesh.

Role of IgM/ IgG Ratio in Distinguishing Primary and Secondary Dengue Viral Infections: A Cross-Sectional Study

Objectives In recent years, Uttarakhand, a state in North India has become one of the prime spots for tourism all over the world. Thereby, a tremendous increase in the epidemics of dengue infection has been observed recently. Secondary dengue causes more severe disease in comparison with primary, thus to differentiate the two is very crucial. We aim to find out the cut-off values of the IgM:IgG ratio for early detection of secondary dengue which could further help clinicians to prevent the complications. Methods A cross-sectional study was conducted over one year involving around 936 suspected cases of dengue. Samples were tested using the commercially available capture enzyme linked Immunosorbent assay (ELISA) method for IgM and IgG. Real-time and nested polymerase chain reaction (PCR) tests were also done to find out the prevalent serotype. IgM:IgG ratio was evaluated by using receiver operating characteristic curve analysis for the differentiation of primary and secondary dengue. Results Among the total 91 serologically confirmed dengue patients, forty-seven (51.6%) were found to be primary, and forty-four (48.4%) were secondary dengue infections with male preponderance. Using the WHO diagnostic criteria, patients with dengue fever (DF) without warning signs added up to 51.6%, with warning signs 42.9% and severe dengue 5.5% of the total cases. The cut-off ratio of IgM:IgG ratio = 1.59 found the best discrimination between primary and secondary infection. Forty out of ninety-one (44%) patients exhibited ratios of > 1.59 whereas the rest fifty-one (56%) exhibited ratios of < 1.59. Dengue virus - 2 (DENV- 2) was found to be the most prevalent serotype. Conclusion Our study recommends the cut-off values for IgM:IgG ratio as 1.59. Therefore it is hoped that this will guide the clinicians to early distinguish between primary and secondary dengue. Furthermore, it can reduce morbidity and mortality because of dengue infections in the future.

Dengue severity by serotype and immune status in 19 years of pediatric clinical studies in Nicaragua

BACKGROUND

Dengue virus, a major global health threat, consists of four serotypes (DENV1-4) that cause a range of clinical manifestations from mild to severe and potentially fatal disease.

METHODS

This study, based on 19 years of data from the Pediatric Dengue Cohort Study and Pediatric Dengue Hospital-based Study in Managua, Nicaragua, investigates the relationship of serotype and immune status with dengue severity. Dengue cases were confirmed by molecular, serological, and/or virological methods, and sudy participants 6 months to 17 years old were followed during their hospital stay or as ambulatory patients.

RESULTS

We enrolled a total of 15,266 participants, of whom 3,227 (21%) were positive for DENV infection. Of 2,630 cases with serotype result by RT-PCR, 557 corresponded to DENV1, 992 to DENV2, 759 to DENV3 and 322 to DENV4. Severe disease was more prevalent among secondary DENV2 and DENV4 cases, while similar disease severity was observed in both primary and secondary DENV1 and DENV3 cases. According to the 1997 World Health Organization (WHO) severity classification, both DENV2 and DENV3 caused a higher proportion of severe disease compared to other serotypes, whereas DENV3 caused the greatest percentage of severity according to the WHO-2009 classification. DENV2 was associated with increased odds of pleural effusion and low platelet count, while DENV3 was associated with both hypotensive and compensated shock.

CONCLUSIONS

These findings demonstrate differences in dengue severity by serotype and immune status and emphasize the critical need for a dengue vaccine with balanced effectiveness against all four serotypes, particularly as existing vaccines show variable efficacy by serotype and serostatus.

The alteration of NK cells phenotypes related to the functions and dengue disease outcomes

Natural killer cells (NK cells) are the front line of immune cells to combat pathogens and able to influence the subsequent adaptive immune responses. One of the factors contributing to pathogenesis in dengue hemorrhagic fever (DHF) disease is aberrant immune activation during early phase of infection. This study explored the profile of NK cells in dengue infected pediatric patients with different degrees of disease severity. DHF patients contained higher frequency of activated NK cells but lower ratio of CD56dim:CD56bright NK subsets. Activated NK cells exhibited alterations in several NK receptors. Interestingly, the frequencies of NKp30 expressing activated NK cells were more pronounced in dengue fever (DF) than in DHF pediatric patients. In vitro functional analysis indicated that degranulation of NK cells in responding to dengue infected dendritic cells (DCs) required cell-cell contact and type I IFNs. Meanwhile, Interferon gamma (IFN-γ) production initially required cell-cell contact and type I IFNs followed by Interleukin-12 (IL-12), Interleukin-15 (IL-15) and Interleukin-18 (IL-18) resulting in the amplification of IFN-γ producing NK cells over time. This study highlighted the complexity and the factors influencing NK cells responses to dengue virus. Degree of activation, phenotypes of activated cells and the crosstalk between NK cells and other immune cells, could modulate the outcome of NK cells function in the dengue disease.

Emergence of Oropouche fever in Latin America: a narrative review

Since its discovery in 1955, the incidence and geographical spread of reported Oropouche virus (OROV) infections have increased. Oropouche fever has been suggested to be one of the most important vector-borne diseases in Latin America. However, both literature on OROV and genomic sequence availability are scarce, with few contributing laboratories worldwide. Three reassortant OROV glycoprotein gene variants termed Iquitos, Madre de Dios, and Perdões virus have been described from humans and non-human primates. OROV predominantly causes acute febrile illness, but severe neurological disease such as meningoencephalitis can occur. Due to unspecific symptoms, laboratory diagnostics are crucial. Several laboratory tests have been developed but robust commercial tests are hardly available. Although OROV is mainly transmitted by biting midges, it has also been detected in several mosquito species and a wide range of vertebrate hosts, which likely facilitates its widespread emergence. However, potential non-human vertebrate reservoirs have not been systematically studied. Robust animal models to investigate pathogenesis and immune responses are not available. Epidemiology, pathogenesis, transmission cycle, cross-protection from infections with OROV reassortants, and the natural history of infection remain unclear. This Review identifies Oropouche fever as a neglected disease and offers recommendations to address existing knowledge gaps, enable risk assessments, and ensure effective public health responses.

Unraveling Dengue Virus Diversity in Asia: An Epidemiological Study through Genetic Sequences and Phylogenetic Analysis

Dengue virus (DENV) is the causative agent of dengue. Although most infected individuals are asymptomatic or present with only mild symptoms, severe manifestations could potentially devastate human populations in tropical and subtropical regions. In hyperendemic regions such as South Asia and Southeast Asia (SEA), all four DENV serotypes (DENV-1, DENV-2, DENV-3, and DENV-4) have been prevalent for several decades. Each DENV serotype is further divided into multiple genotypes, reflecting the extensive diversity of DENV. Historically, specific DENV genotypes were associated with particular geographical distributions within endemic regions. However, this epidemiological pattern has changed due to urbanization, globalization, and climate change. This review comprehensively traces the historical and recent genetic epidemiology of DENV in Asia from the first time DENV was identified in the 1950s to the present. We analyzed envelope sequences from a database covering 16 endemic countries across three distinct geographic regions in Asia. These countries included Bangladesh, Bhutan, India, Maldives, Nepal, Pakistan, and Sri Lanka from South Asia; Cambodia, Laos, Myanmar, Thailand, and Vietnam from Mainland SEA; and Indonesia, the Philippines, Malaysia, and Singapore from Maritime SEA. Additionally, we describe the phylogenetic relationships among DENV genotypes within each serotype, along with their geographic distribution, to enhance the understanding of DENV dynamics.

Dengue viremia kinetics and effects on platelet count and clinical outcomes: An analysis of 2340 patients from Vietnam

Background

Viremia is a critical factor in understanding the pathogenesis of dengue infection, but limited data exist on viremia kinetics. This study aimed to investigate the kinetics of viremia and its effects on subsequent platelet count, severe dengue, and plasma leakage.

Methods

We pooled data from three studies conducted in Vietnam between 2000 and 2016, involving 2340 dengue patients with daily viremia measurements and platelet counts after symptom onset. Viremia kinetics were assessed using a random effects model that accounted for left-censored data. The effects of viremia on subsequent platelet count and clinical outcomes were examined using a landmark approach with a random effects model and logistic regression model with generalized estimating equations, respectively. The rate of viremia decline was derived from the model of viremia kinetics. Its effect on the clinical outcomes was assessed by logistic regression models.

Results

Viremia levels rapidly decreased following symptom onset, with variations observed depending on the infecting serotype. DENV-1 exhibited the highest mean viremia levels during the first 5-6 days, while DENV-4 demonstrated the shortest clearance time. Higher viremia levels were associated with decreased subsequent platelet counts from day 6 onwards. Elevated viremia levels on each illness day increased the risk of developing severe dengue and plasma leakage. However, the effect size decreased with later illness days. A more rapid decline in viremia is associated with a reduced risk of the clinical outcomes.

Conclusions

This study provides comprehensive insights into viremia kinetics and its effect on subsequent platelet count and clinical outcomes in dengue patients. Our findings underscore the importance of measuring viremia levels during the early febrile phase for dengue studies and support the use of viremia kinetics as outcome for phase-2 dengue therapeutic trials.

Funding

Wellcome Trust and European Union Seventh Framework Programme.

Introduction of New Dengue Virus Lineages of Multiple Serotypes after COVID-19 Pandemic, Nicaragua, 2022

Major dengue epidemics throughout Nicaragua's history have been dominated by 1 of 4 dengue virus serotypes (DENV-1-4). To examine serotypes during the dengue epidemic in Nicaragua in 2022, we performed real-time genomic surveillance in-country and documented cocirculation of all 4 serotypes. We observed a shift toward co-dominance of DENV-1 and DENV-4 over previously dominant DENV-2. By analyzing 135 new full-length DENV sequences, we found that introductions underlay the resurgence: DENV-1 clustered with viruses from Ecuador in 2014 rather than those previously seen in Nicaragua; DENV-3, which last circulated locally in 2014, grouped instead with Southeast Asia strains expanding into Florida and Cuba in 2022; and new DENV-4 strains clustered within a South America lineage spreading to Florida in 2022. In contrast, DENV-2 persisted from the formerly dominant Nicaragua clade. We posit that the resurgence emerged from travel after the COVID-19 pandemic and that the resultant intensifying hyperendemicity could affect future dengue immunity and severity.

An Observational Study to Find the Association of Viral Load, NS1 Antigen, IgG Antibody, and Other Laboratory Parameters With the Outcome of Dengue Patients in Eastern India

Background Dengue, the mosquito-borne febrile disease caused by the dengue virus, has become one of the major concerns of public health. It may present with only fever, or there may be a hemorrhagic manifestation or septic shock. As there is no specific treatment for dengue, early detection of the disease, assessment of progression, and prediction of outcome by studying the laboratory markers will help guide the management of cases and lower morbidity and mortality. Methodology This clinico-observational study was conducted at the Department of Microbiology in a tertiary care hospital in Kolkata, India, from February 2020 to August 2022 to determine the outcome of dengue patients in correlation with viral load, NS1 antigen, IgM and IgG antibodies, ferritin level, platelet count, and other laboratory parameters. Results Out of 316 samples from fever patients, 103 (32.5%) were NS1 antigen reactive. We followed up the dengue patients (n = 103) for 15 days and divided them into three groups according to their duration of symptoms (group A suffered for ≤5 days, group B for 5 to 10 days, and group C for >10 days) and per the WHO classification of disease severity, namely dengue without warning signs (DOS), dengue with warning signs (DWS), and severe dengue (SD). Based on severity, 65 (63.1%) patients had DOS, whereas 31 (30.09%) patients had DWS, and seven (6.79%) patients had SD. Secondary infection was present in 83.33% of patients in group C, 71% of DWS cases, and 57% of SD cases, which positively correlates with liver enzymes, viral load (mean value 102195 in secondary infection vs. 1195 copies/10 µl in primary infection), and negatively correlates with platelet counts (mean value 60,213 in secondary infection vs. 1,25,516 in primary infection). Patients in group C had higher liver enzymes, a lower platelet count, and a higher initial viral load than groups A and B. Similarly, SD cases had a higher ferritin level (9215 ug/l), a lower platelet count (mean value 23,250), and a higher initial viral load (mean value 2,74,257 copies/10 µl). An increase in hematocrit value considering the peak value and its baseline value is an important marker for disease severity rather than its absolute value. Conclusion Poor outcome of dengue infection, i.e., an increase in the duration of symptoms and disease severity depends on concurrent associations between high serum ferritin, increased hematocrit level, thrombocytopenia, secondary infection, increasing liver enzymes, and increased initial viral load.

Within-host models unravelling the dynamics of dengue reinfections

Caused by four serotypes, dengue fever is a major public health concern worldwide. Current modeling efforts have mostly focused on primary and heterologous secondary infections, assuming that lifelong immunity prevents reinfections by the same serotype. However, recent findings challenge this assumption, prompting a reevaluation of dengue immunity dynamics. In this study, we develop a within-host modeling framework to explore different scenarios of dengue infections. Unlike previous studies, we go beyond a deterministic framework, considering individual immunological variability. Both deterministic and stochastic models are calibrated using empirical data on viral load and antibody (IgM and IgG) concentrations for all dengue serotypes, incorporating confidence intervals derived from stochastic realizations. With good agreement between the mean of the stochastic realizations and the mean field solution for each model, our approach not only successfully captures primary and heterologous secondary infection dynamics facilitated by antibody-dependent enhancement (ADE) but also provides, for the first time, insights into homotypic reinfection dynamics. Our study discusses the relevance of homotypic reinfections in dengue transmission at the population level, highlighting potential implications for disease prevention and control strategies.

Kinetics of dengue viremia and its association with disease severity: an ambispective study

Background

Dengue virus (DENV) infection is an important public health problem and causes significant morbidity and mortality. DENV typically causes a febrile illness that ranges from mild asymptomatic infection to fatal dengue hemorrhagic fever (DHF) and/or dengue shock syndrome (DSS). Early prediction of severe dengue disease is of utmost importance for providing prompt monitoring and treatment. The search for an ideal biomarker (host or viral factors) for early prediction of severe dengue remains elusive.

Aim

To standardize a real time qRT-PCR for quantifying dengue viremia in serum samples and evaluate the kinetics of dengue viremia and its significance in disease severity.

Results

In this ambispective study of 126 laboratory confirmed dengue patients, 72 were primary infections and 54 were secondary infections. The most common serotype was serotype 1 (n = 37) followed by serotype 2 (n = 34). According to WHO 1997 dengue case classification, 111 patients were cases of dengue fever (DF), 13 from DHF and 02 from DSS. Day 3 viremia levels were significantly elevated in severe dengue patients (DHF/DSS) as compared to that of DF (p < 0.05). However, no such association was found between viremia levels and serotype or immune status.

Conclusion

Dengue viremia has a significant association with disease severity and day 3 viremia levels may be used as a predictor for dengue disease severity.

Demographic and clinical features of dengue fever infection in Pakistan: a cross-sectional epidemiological study

BACKGROUND

Dengue fever caused by dengue virus is a tropical disease and is among the deadliest vector-borne diseases. The humid and hot summers of Pakistan support the probation of the vectors responsible for the transmission of viral and other parasitic diseases.

METHODOLOGY

A retrospective study, from 2012- 2019, of dengue infected individuals from the Punjab province of Pakistan was carried out to analyze epidemiology, clinical and laboratory findings of subjects with dengue virus infection. Data was derived from National Institute of Health (NIH) followed by Dengue control program of Pakistan, covering the incidence rate in 36 districts of Punjab and Islamabad Capital Territory (ICT) respectively. Patients data including the presence of dengue specific antigen or/and antibodies such as NS1 and IgG/IgM were observed. The study also included the analysis of demographic data, geographic data, and the month-wise distribution of dengue cases to examine seasonal trends.

RESULTS

We analyzed 25,682 dengue infected individuals. The statistical analysis revealed a significant association between genders in which male population was more affected by dengue than females. It was also noted that the middle age group was the most affected age group while the highest number of cases were reported in October. Rawalpindi and Lahore were the most affected cities in Punjab province while Islamabad represented the highest number of cases during the recent outbreak in 2019. The IgM and IgG antibodies were highly prevalent among the infected patients.

CONCLUSION

Dengue is endemic in Pakistan, circulating throughout the year. Highest number of cases were observed in the month of October, September and November respectively. Association between climate change and vector-borne diseases need to be investigated in Pakistan as they significantly influence the timing and intensity of dengue and other disease outbreaks. Further exploration of hematological parameters is required to better diagnose and treat the disease. For the effective control of dengue outbreaks, awareness campaigns on sewage management and vector control along with social factors are strongly recommended for better control and eradication of the disease.

About contamination by sterile females and residual male fertility on the effectiveness of the sterile insect technique. Impact on disease vector control and disease control

The sterile insect technique (SIT) is a technique to control pests and vectors of diseases by releasing mainly sterile males. Several challenges need to be solved before large-scale field application in order to guarantee its success. In this paper we intend to focus on two important issues: residual fertility in released (sterile) males and contamination of each release by sterile females. Indeed, sterile males are never 100% sterile, that is there is always a small proportion, ɛ, of fertile males (sperm of) within the sterile males population. Among the sterile insects that are released, a certain proportion, ϵF, of them are sterile females due to imperfect mechanical sex-separation technique. This can be particularly problematic when arthropod viruses are circulating, because mosquito females, even sterile, are vectors of diseases. Various upper bound values are given in the entomological literature for ϵF and ɛ without clear explanations. In this work, we aim to show that these values are related to the biological parameters of the targeted vector, the sterile insects release rate, and the epidemiological parameters of a vector-borne disease, like Dengue. We extend results studied separately in Aronna and Dumont (2020), Dumont and Yatat-Djeumen (2022). To study the impact of both issues, we develop and study a SIT-entomological-epidemiological mathematical model, with application to Dengue. Qualitative analysis of the model is carried out to highlight threshold values that shape the overall dynamics of the system. We show that vector elimination is possible only when Nɛ<1, where N is the basic-offspring number related to the targeted wild population. To ensure the success of SIT control, we recommend that the issue of residual fertility be addressed as a priority and then that contamination by sterile females be minimized with each release.

[Clinical Update on Diagnosis, Treatment and Prevention of Dengue]

Dengue is a vector-borne disease that has a significant impact on global public health. The vector mosquito belongs to the genus Aedes. Two species play a key role in human transmission: Ae. aegypti, which has adapted to the urban environment of highly populated areas in tropical and subtropical countries, leading to a dramatic increase in dengue cases over the years, and Ae. albopictus, which poses a potential threat to temperate climate countries due to its ability to adapt to colder climates. The disease is widespread across the world, posing a risk to nearly half of the world's population. Although most cases are asymptomatic, dengue causes a burden on healthcare systems and mainly affects the younger population. The disease is also spreading to temperate climate countries, thus becoming a global threat. Vector control measures and vaccine development have been the main prevention strategies, as there is still no effective treatment for the disease.

Computational Advancement towards the Identification of Natural Inhibitors for Dengue Virus: A Brief Review

Viral infectious illnesses represent a severe hazard to human health due to their widespread incidence worldwide. Among these ailments, the dengue virus (DENV) infection stands out. World Health Organization (WHO) estimates that DENV infection affects ~400 million people each year, with potentially fatal symptoms showing up in 1% of the cases. In several instances, academic and pharmaceutical researchers have conducted several pilot and clinical studies on a variety of topics, including viral epidemiology, structure and function analyses, infection source and route, therapeutic targets, vaccinations, and therapeutic drugs. Amongst Takeda, TAK-003, Sanofi, Dengvaxia®, and Butantan/NIH/Merck, Dengvaxia® (CYD-TDV) is the only licensed vaccination yet; however, the potential inhibitors are under development. The biology and evolution of DENVs are briefly discussed in this review, which also compiles the most recent studies on prospective antiviral targets and antiviral candidates. In conclusion, the triumphs and failures have influenced the development of anti-DENV medications, and the findings in this review article will stimulate more investigation.

Markers of prolonged hospitalisation in severe dengue

BACKGROUND

Dengue is one of the most common diseases in the tropics and subtropics. Whilst mortality is a rare event when adequate supportive care can be provided, a large number of patients get hospitalised with dengue every year that places a heavy burden on local health systems. A better understanding of the support required at the time of hospitalisation is therefore of critical importance for healthcare planning, especially when resources are limited during major outbreaks.

METHODS

Here we performed a retrospective analysis of clinical data from over 1500 individuals hospitalised with dengue in Vietnam between 2017 and 2019. Using a broad panel of potential biomarkers, we sought to evaluate robust predictors of prolonged hospitalisation periods.

RESULTS

Our analyses revealed a lead-time bias, whereby early admission to hospital correlates with longer hospital stays - irrespective of disease severity. Importantly, taking into account the symptom duration prior to hospitalisation significantly affects observed associations between hospitalisation length and previously reported risk markers of prolonged stays, which themselves showed marked inter-annual variations. Once corrected for symptom duration, age, temperature at admission and elevated neutrophil-to-lymphocyte ratio were found predictive of longer hospitalisation periods.

CONCLUSION

This study demonstrates that the time since dengue symptom onset is one of the most significant predictors for the length of hospital stays, independent of the assigned severity score. Pre-hospital symptom durations need to be accounted for to evaluate clinically relevant biomarkers of dengue hospitalisation trajectories.

Facing the escalating burden of dengue: Challenges and perspectives

Dengue is the most rapidly emerging mosquito-borne infection and, due to climate change and unplanned urbanization, it is predicted that the global burden of dengue will rise further as the infection spreads to new geographical locations. Dengue-endemic countries are often unable to cope with such increases, with health care facilities becoming overwhelmed during each dengue season. Furthermore, although dengue has been predominantly a childhood illness in the past, it currently mostly affects adults in many countries, with higher incidence of severe disease and mortality rates in pregnant women and in those with comorbidities. As there is currently no specific treatment for dengue and no early biomarker to identify those who will progress to develop vascular leakage, all individuals with dengue are closely monitored in case they need fluid management. Furthermore, diagnosing patients with acute dengue is challenging due to the similarity of clinical symptoms during early illness and poor sensitivity and specificity of point-of-care diagnostic tests. Novel vector control methods, such as the release of Wolbachia-infected mosquitoes, have shown promising results by reducing vector density and dengue incidence in clinical trial settings. A new dengue vaccine, TAK-003, had an efficacy of 61.2% against virologically confirmed dengue, 84.1% efficacy against hospitalizations and a 70% efficacy against development of dengue haemorrhagic fever (DHF) at 54 months. While vaccines and mosquito control methods are welcome, they alone are unlikely to fully reduce the burden of dengue, and a treatment for dengue is therefore essential. Several novel antiviral drugs are currently being evaluated along with drugs that inhibit host mediators, such as mast cell products. Although viral proteins such as NS1 contribute to the vascular leak observed in severe dengue, the host immune response to the viral infection also plays a significant role in progression to severe disease. There is an urgent need to discover safe and effective treatments for dengue to prevent disease progression.

A Novel, Comprehensive A129 Mouse Model for Investigating Dengue Vaccines and Evaluating Pathogenesis

In search of a mouse model for use in evaluating dengue vaccines, we assessed A129 mice that lacked IFN-α/β receptors, rendering them susceptible to dengue virus (DENV) infection. To our knowledge, no reports have evaluated dengue vaccine efficiency using A129 mice. A129 mice were given a single intraperitoneal (IP) or subcutaneous (SC) injection of the vaccine, Dengvaxia. After 14 days of immunization via the IP or SC injection of Dengvaxia, the A129 mice exhibited notably elevated levels of anti-DENV immunoglobulin G and neutralizing antibodies (NAb) targeting all four DENV serotypes, with DENV-4 displaying the highest NAb levels. After challenge with DENV-2, Dengvaxia and mock-immunized mice survived, while only the mock group exhibited signs of morbidity. Viral genome levels in the serum and tissues (excluding the brain) were considerably lower in the immunized mice compared to those in the mock group. The SC administration of Dengvaxia resulted in lower viremia levels than IP administration did. Therefore, given that A129 mice manifest dengue-related morbidity, including viremia in the serum and other tissues, these mice represent a valuable model for investigating novel dengue vaccines and antiviral drugs and for exploring dengue pathogenesis.

Modelling the impact of JNJ-1802, a first-in-class dengue inhibitor blocking the NS3-NS4B interaction, on in-vitro DENV-2 dynamics

Dengue virus (DENV) is a public health challenge across the tropics and subtropics. Currently, there is no licensed prophylactic or antiviral treatment for dengue. The novel DENV inhibitor JNJ-1802 can significantly reduce viral load in mice and non-human primates. Here, using a mechanistic viral kinetic model calibrated against viral RNA data from experimental in-vitro infection studies, we assess the in-vitro inhibitory effect of JNJ-1802 by characterising infection dynamics of two DENV-2 strains in the absence and presence of different JNJ-1802 concentrations. Viral RNA suppression to below the limit of detection was achieved at concentrations of >1.6 nM, with a median concentration exhibiting 50% of maximal inhibitory effect (IC50) of 1.23x10-02 nM and 1.28x10-02 nM for the DENV-2/RL and DENV-2/16681 strains, respectively. This work provides important insight into the in-vitro inhibitory effect of JNJ-1802 and presents a first step towards a modelling framework to support characterization of viral kinetics and drug effect across different host systems.

Dengue havoc: overview and eco-friendly strategies to forestall the current epidemic

Dengue fever is a mosquito-borne viral illness that affects over 100 nations around the world, including Africa, America, the Eastern Mediterranean, Southeast Asia, and the Western Pacific. Those who get infected by virus for the second time are at greater risk of having persistent dengue symptoms. Dengue fever has yet to be treated with a long-lasting vaccination or medication. Because of their ease of use, mosquito repellents have become popular as a dengue prevention technique. However, this has resulted in environmental degradation and harm, as well as bioaccumulation and biomagnification of hazardous residues in the ecosystem. Synthetic pesticides have caused a plethora of serious problems that were not foreseen when they were originally introduced. The harm caused by the allopathic medications/synthetic pesticides/chemical mosquito repellents has paved the door to employment of eco-friendly/green approaches in order to reduce dengue cases while protecting the integrity of the nearby environment too. Since the cases of dengue have become rampant these days, hence, starting the medication obtained from green approaches as soon as the disease is detected is advisable. In the present paper, we recommend environmentally friendly dengue management strategies, which, when combined with a reasonable number of vector control approaches, may help to avoid the dengue havoc as well as help in maintaining the integrity of the ecosystem.

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

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

Viremia and Inflammatory Cytokines in Dengue: Interleukin-2 as a Biomarker of Infection, and Interferon-α and -γ as Markers of Primary versus Secondary Infection

The pathogenesis of Dengue virus (DENV) infection is complex and involves viral replication that may trigger an inflammatory response leading to severe disease. Here, we investigated the correlation between viremia and cytokine levels in the serum of DENV-infected patients. Between 2013 and 2014, 138 patients with a diagnosis of acute-phase DENV infection and 22 patients with a non-dengue acute febrile illness (AFI) were enrolled. Through a focus-forming assay (FFU), we determined the viremia levels in DENV-infected patients and observed a peak in the first two days after the onset of symptoms. A higher level of viremia was observed in primary versus secondary DENV-infected patients. Furthermore, no correlation was observed between viremia and inflammatory cytokine levels in DENV-infected patients. Receiver operating characteristic (ROC) curve analysis revealed that IL-2 has the potential to act as a marker to distinguish dengue from other febrile illnesses and is positively correlated with Th1 cytokines. IFN-α and IFN-γ appear to be potential markers of primary versus secondary infection in DENV-infected patients, respectively. The results also indicate that viremia levels are not the main driving force behind inflammation in dengue and that cytokines could be used as infection biomarkers and for differentiation between primary versus secondary infection.

Antibody Profiling of Dengue Severities Using Flavivirus Protein Microarrays

Dengue is a viral disease transmitted by Aedes aegypti mosquitoes. According to the World Health Organization, about half of the world's population is at risk of dengue. There are four serotypes of the dengue virus. After infection with one serotype, it will be immune to such a serotype. However, subsequent infection with other serotypes will increase the risk of severe outcomes, e.g., dengue hemorrhagic fever, dengue shock syndrome, and even death. Since severe dengue is challenging to predict and lacks molecular markers, we aim to build a multiplexed Flavivirus protein microarray (Flaviarray) that includes all of the common Flaviviruses to profile the humoral immunity and cross-reactivity in the dengue patients with different outcomes. The Flaviarrays we fabricated contained 17 Flavivirus antigens with high reproducibility (R-square = 0.96) and low detection limits (172-214 pg). We collected serums from healthy subjects (n = 36) and dengue patients within 7 days after symptom onset (mild dengue (n = 21), hospitalized nonsevere dengue (n = 29), and severe dengue (n = 36)). After profiling the serum antibodies using Flaviarrays, we found that patients with severe dengue showed higher IgG levels against multiple Flavivirus antigens. With logistic regression, we found groups of markers with high performance in distinguishing dengue patients from healthy controls as well as hospitalized from mild cases (AUC > 0.9). We further reported some single markers that were suitable to separate dengue patients from healthy controls (AUC > 0.9) and hospitalized from mild outcomes (AUC > 0.8). Together, Flaviarray is a valuable tool to profile antibody specificities, uncover novel markers for decision-making, and shed some light on early preventions and treatments.

Utility of CDC DENV1-4 real time PCR assay and trioplex assay for the diagnosis of dengue in patients with acute febrile illness

Nucleic acid amplification tests (NAATs) have revolutionized reliable detection of dengue virus (DENV) during acute phase of infection. The study evaluated performance of CDC DENV-1-4 real-time assay, trioplex RT-PCR and heminested conventional RT-PCR assay in the diagnosis of DENV. The three NAATs were performed on 107 consecutive samples collected from patients suspected of DENV infection during acute phase of illness. Their performance was compared against composite reference standard, consisting of DENV NS1 antigen ELISA and DENV IgM ELISA. 88/107 study samples were positive by DENV ELISA, either NS1Ag (80), IgM (3) or both (5). The overall sensitivity of CDC DENV-1-4 RT-PCR assay, trioplex RT-PCR assay and conventional multiplex RT-PCR was 68.18%, 54.55% and 38.64%, respectively in diagnosing dengue during acute phase, with an area under the curve of 0.841, 0.773 and 0.693 respectively when compared against composite reference standard. The sensitivity was 82.93%, 73.17% and 51.22%, respectively within three days of illness and 60%, 42.86% and 28.57%, respectively between 4 and 5th day of illness. All the three molecular assays had 100% specificity. Maximum concordance values of 86.9% were recorded among CDC DENV-1-4 rRT-PCR assay and trioplex assay with kappa value of 0.74, suggestive of substantial agreement. CDC DENV-1-4 rRT-PCR assay can be used as a reliable and accurate test for diagnosis of DENV during acute phase of illness.

Serotype-associated immune response and network immunoclusters in children and adults during acute Dengue virus infection

The present study was designed as an exploratory investigation to characterize the overall profile of chemokines, growth factors, and pro-inflammatory/regulatory cytokines during acute DENV infection according to DENV-1, DENV-2, DENV-4 serotypes and age: children: <1-10-year-old (yo); adolescents:11-20 yo; adults 21-40 yo; and older adults: 41-75 yo. The levels of soluble immunemediators were measured in serum by high-throughput microbeads array in 636 subjects including 317 DENV-infected and 319 age-matching non-infected control (NI). Overall, most soluble mediators were increased in DENV-infected patients as compared to NI group regardless of age and DENV serotype, with high magnitude order of increase for CCL2, CXCL10, IL-1β, IFN-γ, IL1-Ra (fold change >3x), except PDGF in which no fold change was observed. Moreover, despite the age ranges, DENV-1 and DENV-4 presented increased levels of VEGF, IL-6, and TNF-α in serum but decreased levels of PDGF, while DENV-2 exhibited increased levels of CXCL8, CCL4, and IL-12. Noteworthy was that DENV-2 showed increased levels of IL-12, IL-15, IL-17, IL-4, IL-9, and IL-13, and maintained an unaltered levels of PDGF at younger ages (<1-10 yo and 11-20 yo), whereas in older ages (21-40 yo and 41-75 yo), the results showed increased levels of CCL2, IL-6, and TNF-α, but lower levels of PDGF. In general, DENV infection at younger age groups exhibited more complex network immunoclusters as compared to older age groups. Multivariate analysis revealed a clustering of DENV cases according to age for a set of soluble mediators especially in subjects infected with DENV-2 serotype. Altogether, our findings demonstrate that the profile of circulating soluble mediators differs substantially in acute DENV according to age and DENV serotypes suggesting the participation of serotype-associated immune response, which may represent a potential target for development of therapeutics and could be used to assist medical directive for precise clinical management of severe cases.

The increasing complexity of arbovirus serology: An in-depth systematic review on cross-reactivity

Diagnosis of arbovirus infection or exposure by antibody testing is becoming increasingly difficult due to global expansion of arboviruses, which induce antibodies that may (cross-)react in serological assays. We provide a systematic review of the current knowledge and knowledge gaps in differential arbovirus serology. The search included Medline, Embase and Web of Science databases and identified 911 publications which were reduced to 102 after exclusion of studies not providing data on possible cross-reactivity or studies that did not meet the inclusion criteria regarding confirmation of virus exposure of reference population sets. Using a scoring system to further assess quality of studies, we show that the majority of the selected papers (N = 102) provides insufficient detail to support conclusions on specificity of serological outcomes with regards to elucidating antibody cross-reactivity. Along with the lack of standardization of assays, metadata such as time of illness onset, vaccination, infection and travel history, age and specificity of serological methods were most frequently missing. Given the critical role of serology for diagnosis and surveillance of arbovirus infections, better standards for reporting, as well as the development of more (standardized) specific serological assays that allow discrimination between exposures to multiple different arboviruses, are a large global unmet need.

Antiviral Activities of Streptomyces KSF 103 Methanolic Extracts against Dengue Virus Type-2

Dengue has long been a serious health burden to the global community, especially for those living in the tropics. Despite the availability of vaccines, effective treatment for the infection is still needed and currently remains absent. In the present study, the antiviral properties of the Streptomyces sp. KSF 103 methanolic extract (Streptomyces KSF 103 ME), which consists of a number of potential antiviral compounds, were investigated against dengue virus serotype 2 (DENV-2). The effects of this extract against DENV-2 replication were determined using the quantitative Real Time-Polymerase Chain Reaction (qRT-PCR). Findings from the study suggested that the Streptomyces KSF 103 ME showed maximum inhibitory properties toward the virus during the virus entry stage at concentrations of more than 12.5 µg/mL. Minimal antiviral activities were observed at other virus replication stages; adsorption (42% reduction at 50 µg/mL), post-adsorption (67.6% reduction at 50 µg/mL), prophylactic treatment (68.4% and 87.7% reductions at 50 µg/mL and 25 µg/mL, respectively), and direct virucidal assay (48% and 56.8% reductions at 50 µg/mL and 25 µg/mL, respectively). The Streptomyces KSF 103 ME inhibited dengue virus replication with a 50% inhibitory concentration (IC50) value of 20.3 µg/mL and an International System of Units (SI) value of 38.9. The Streptomyces KSF 103 ME showed potent antiviral properties against dengue virus (DENV) during the entry stage. Further studies will be needed to deduce the antiviral mechanisms of the Streptomyces KSF 103 ME against DENV.