Current advances in dengue diagnosis

Exploring Central Venous Thrombosis as a Rare Postinfectious Complication of Dengue: A Case Report

Dengue fever, caused by a flavivirus transmitted through Aedes mosquitoes, presents a spectrum of clinical manifestations ranging from mild to severe. Several neurological complications, including encephalopathy and encephalitis, have been increasingly recognized. Here, we report a case of central venous thrombosis (CVT) as a postinfectious complication of dengue fever. A 38-year-old previously healthy male presented with classic dengue symptoms and later developed persistent headaches and visual disturbances. Neurological examination revealed papilledema, and imaging confirmed CVT involving the superior straight sinus. Prompt initiation of anticoagulant therapy led to gradual improvement in neurological symptoms and partial recanalization of the thrombosed sinus. Our case underscores the importance of considering thrombotic complications in dengue infections, despite the predominance of hemorrhagic manifestations. Understanding pathophysiology and appropriate management of thrombotic events in dengue fever is crucial for favorable patient outcomes.

Comprehensive evaluation on progressive development strategies in DENV surveillance and monitoring infection rate among vector population

The elevated rise in dengue infection rate has been a health burden worldwide and it will continue to impact global health for years to come. Accumulated literature holds accountable the geographical expansion of the mosquito species transmitting the dengue virus DENV. The frequency of this viral disease outbreaks has increased rapidly in the recent years, owing to various geo-climatic and anthropological activities. Due to scarcity of any effective control measures, there has been a continuous traceable rise in mortality and morbidity rates. However, it has been reported that the spate of incidences is directly related to density of the virus infected vector (mosquito) population in a given region. In such a scenario, systems capable of detecting virus infected vector population would aid in estimating prediction of outbreak, as well as provide time to deploy suitable management strategies for vector control, and to break the vector-human transmission chain. This would also help in identifying areas, where much improvement is needed for vector management. To this context, we illustrate an exhaustive overview of both gold standards and as well as emerging advents for sensitive and specific mosquito population strategized viral detection technologies. We summarize the cutting-edge technologies and the challenges faced in pioneering to field application. Regardless the proven popularity of the gold standards for detection purpose, they offer certain limitations. Thus with the surge in the infection rate globally, approaches for development of newer advancements and technique upgradation to arrest the infection escalation and for early detection as a part of vector management should be prioritized.

Serological and molecular detection of dengue virus in animals: A systematic review and meta-analysis

Introduction

Dengue is a vector-borne disease, especially important in tropical and subtropical areas. The first presentation of many arboviral diseases occurred mainly in animals, including multiple Alphaviruses and Flaviviruses, such as dengue.

Objective

To determine the serological and molecular frequency of the dengue virus in animals.

Methods

A systematic literature review was carried out in five databases for the proportion of animals infected with dengue, defined by molecular and serological tests. A meta-analysis was performed using a random-effects model to calculate the pooled prevalence and 95% confidence intervals (CI). Cochran?s Q test and the I2 statistic were used to assess the heterogeneity between the two studies.

Results

The presence of dengue in bats, primates, birds, sheep, horses, cattle, pigs, rodents and buffaloes, according to serological methods, had a prevalence of 10%, 29%, 8%, 1%, 11%, 0%, 49%, 2%, 7%, respectively. According to molecular methods, the presence of dengue in bats had a seroprevalence of 6.0%.

Conclusion

The present study confirms the presence of the Dengue virus in a large group of animal species, with potential implications as possible reservoirs of this virus, raising the possibility of zoonotic transmission.

DengueSeq: a pan-serotype whole genome amplicon sequencing protocol for dengue virus

BACKGROUND

The increasing burden of dengue virus on public health due to more explosive and frequent outbreaks highlights the need for improved surveillance and control. Genomic surveillance of dengue virus not only provides important insights into the emergence and spread of genetically diverse serotypes and genotypes, but it is also critical to monitor the effectiveness of newly implemented control strategies. Here, we present DengueSeq, an amplicon sequencing protocol, which enables whole-genome sequencing of all four dengue virus serotypes.

RESULTS

We developed primer schemes for the four dengue virus serotypes, which can be combined into a pan-serotype approach. We validated both approaches using genetically diverse virus stocks and clinical specimens that contained a range of virus copies. High genome coverage (>95%) was achieved for all genotypes, except DENV2 (genotype VI) and DENV 4 (genotype IV) sylvatics, with similar performance of the serotype-specific and pan-serotype approaches. The limit of detection to reach 70% coverage was 10-100 RNA copies/μL for all four serotypes, which is similar to other commonly used primer schemes. DengueSeq facilitates the sequencing of samples without known serotypes, allows the detection of multiple serotypes in the same sample, and can be used with a variety of library prep kits and sequencing instruments.

CONCLUSIONS

DengueSeq was systematically evaluated with virus stocks and clinical specimens spanning the genetic diversity within each of the four dengue virus serotypes. The primer schemes can be plugged into existing amplicon sequencing workflows to facilitate the global need for expanded dengue virus genomic surveillance.

DengueSeq: A pan-serotype whole genome amplicon sequencing protocol for dengue virus

Background

The increasing burden of dengue virus on public health due to more explosive and frequent outbreaks highlights the need for improved surveillance and control. Genomic surveillance of dengue virus not only provides important insights into the emergence and spread of genetically diverse serotypes and genotypes, but it is also critical to monitor the effectiveness of newly implemented control strategies. Here, we present DengueSeq, an amplicon sequencing protocol, which enables whole-genome sequencing of all four dengue virus serotypes.

Results

We developed primer schemes for the four dengue virus serotypes, which can be combined into a pan-serotype approach. We validated both approaches using genetically diverse virus stocks and clinical specimens that contained a range of virus copies. High genome coverage (>95%) was achieved for all genotypes, except DENV2 (genotype VI) and DENV 4 (genotype IV) sylvatics, with similar performance of the serotype-specific and pan-serotype approaches. The limit of detection to reach 70% coverage was 101-102 RNA copies/μL for all four serotypes, which is similar to other commonly used primer schemes. DengueSeq facilitates the sequencing of samples without known serotypes, allows the detection of multiple serotypes in the same sample, and can be used with a variety of library prep kits and sequencing instruments.

Conclusions

DengueSeq was systematically evaluated with virus stocks and clinical specimens spanning the genetic diversity within each of the four dengue virus serotypes. The primer schemes can be plugged into existing amplicon sequencing workflows to facilitate the global need for expanded dengue virus genomic surveillance.

A novel colorimetric biosensor for rapid detection of dengue virus upon acid-induced aggregation of colloidal gold

The dengue virus, once transmitted to people through a mosquito bite, causes an infectious disease called dengue fever. Dengue fever can develop into two fatal syndromes, namely dengue shock syndrome and dengue hemorrhagic fever. The existing strategies for detecting dengue infection mainly employ serological immunoassays and a real time PCR technique. Along with the positive features of efficiency, accuracy, and reproducibility, these procedures are limited by being time-consuming, costly, requiring special equipment for analysis, and unable to be carried out at the point-of-care level. Herein, we developed a colorimetric nanosensor for detecting dengue virus in clinical samples that is rapid, accurate, sensitive, and less expensive. The sensing platform relies on the specific binding between the DNA-conjugated AuNPs and genomic RNA of dengue, which results in the DNA-RNA heteroduplex structure formation that turns the gold colloid's ruby red color to blue due to the nano-aggregation in an acidic environment, which can be detected by the naked eye or measuring the absorbance. The DNA probe was designed to bind to a genomic RNA conserved region recognized in all four dengue serotypes. Dengue virus serotype 1 was utilized as a framework for virus detection; the designed nanosensor exhibited great specificity and selectivity, with the detection limit of ∼1 pg μL-1 (∼1.66 × 106 RNA copies per reaction) and time of analysis of about 1 h including the RNA extraction step. The proposed colorimetric nanosensor offers an alternative tool for specific and highly sensitive detection of dengue that eliminates the requirement for thermal cycling and primer sets in PCR-based assays.

Diagnostic approaches for dengue infection

INTRODUCTION

Every year, a significant rise in dengue incidence observed is responsible for 10% of fever episodes in children and adolescents in endemic countries. Considering that the symptoms of dengue are similar to those of many other viruses, early diagnosis of the disease has long been difficult, and lack of sensitive diagnostic tools may be another factor contributing to a rise in dengue incidence.

AREAS COVERED

This review will highlight dengue diagnostics strategies and discuss other possible targets for dengue diagnosis. Understanding the dynamics of the immune response and how it affects viral infection has enabled informed diagnosis. As more technologies emerge, precise assays that include some clinical markers need to be included.

EXPERT OPINION

Future diagnostic strategies will require the use both viral and clinical markers in a serial manner with the use of artificial intelligence technology to determine from the first point of illness to better determine severity status and management. A definitive endpoint is not in the horizon as the disease as well as the virus is constantly evolving and hence many developed assays need to be constantly changing some of their reagents periodically as newer genotypes and probably too serotypes emerge.

Integrated clinical and metabolomic analysis of dengue infection shows molecular signatures associated with host-pathogen interaction in different phases of the disease

PURPOSE

Dengue is a mosquito vector-borne disease caused by the dengue virus, which affects 125 million people globally. The disease causes considerable morbidity. The disease, based on symptoms, is classified into three characteristic phases, which can further lead to complications in the second phase. Molecular signatures that are associated with the three phases have not been well characterized. We performed an integrated clinical and metabolomic analysis of our patient cohort and compared it with omics data from the literature to identify signatures unique to the different phases.

METHODS

The dengue patients are recruited by clinicians after standard-of-care diagnostic tests and evaluation of symptoms. Blood from the patients was collected. NS1 antigen, IgM, IgG antibodies, and cytokines in serum were analyzed using ELISA. Targeted metabolomics was performed using LC-MS triple quad. The results were compared with analyzed transcriptomic data from the GEO database and metabolomic data sets from the literature.

RESULTS

The dengue patients displayed characteristic features of the disease, including elevated NS1 levels. TNF-α was found to be elevated in all three phases compared to healthy controls. The metabolic pathways were found to be deregulated compared to healthy controls only in phases I and II of dengue patients. The pathways represent viral replication and host response mediated pathways. The major pathways include nucleotide metabolism of various amino acids and fatty acids, biotin, etc. CONCLUSION: The results show elevated TNF-α and metabolites that are characteristic of viral infection and host response. IL10 and IFN-γ were not significant, consistent with the absence of any complications.

Laboratory Evaluation and Field Testing of Dengue NS1 and IgM/IgG Rapid Diagnostic Tests in an Epidemic Context in Senegal

In Senegal, the burden of dengue is increasing and expanding. As case management and traditional diagnostic techniques can be difficult to implement, rapid diagnostic tests (RDTs) deployed at point of care are ideal for investigating active outbreaks. The aim of this study was to evaluate the diagnostic performance of the Dengue NS1 and Dengue IgM/IgG RDTs on the serum/plasma samples in a laboratory setting and in the field. During laboratory evaluation, performance of the NS1 RDT was assessed using NS1 ELISA as the gold standard. Sensitivity and specificity were 88% [75–95%] and 100% [97–100%], respectively. Performance of the IgM/IG RDT was assessed using the IgM Antibody Capture (MAC) ELISA, indirect IgG, and PRNT as gold standards. The IgM and IgG test lines respectively displayed sensitivities of 94% [83–99%] and 70% [59–79%] and specificities of 91% [84–95%] and 91% [79–98%]. In the field, the Dengue NS1 RDT sensitivity and specificity was 82% [60–95%] and 75% [53–90%], respectively. The IgM and IgG test lines displayed sensitivities of 86% [42–100%] and 78% [64–88%], specificities of 85% [76–92%] and 55% [36–73%], respectively. These results demonstrate that RDTs are ideal for use in a context of high prevalence or outbreak setting and can be implemented in the absence of a confirmatory test for acute and convalescent patients.

Serological cross-reactivity among common flaviviruses

The Flavivirus genus is made up of viruses that are either mosquito-borne or tick-borne and other viruses transmitted by unknown vectors. Flaviviruses present a significant threat to global health and infect up to 400 million of people annually. As the climate continues to change throughout the world, these viruses have become prominent infections, with increasing number of infections being detected beyond tropical borders. These include dengue virus (DENV), West Nile virus (WNV), Japanese encephalitis virus (JEV), and Zika virus (ZIKV). Several highly conserved epitopes of flaviviruses had been identified and reported to interact with antibodies, which lead to cross-reactivity results. The major interest of this review paper is mainly focused on the serological cross-reactivity between DENV serotypes, ZIKV, WNV, and JEV. Direct and molecular techniques are required in the diagnosis of Flavivirus-associated human disease. In this review, the serological assays such as neutralization tests, enzyme-linked immunosorbent assay, hemagglutination-inhibition test, Western blot test, and immunofluorescence test will be discussed. Serological assays that have been developed are able to detect different immunoglobulin isotypes (IgM, IgG, and IgA); however, it is challenging when interpreting the serological results due to the broad antigenic cross-reactivity of antibodies to these viruses. However, the neutralization tests are still considered as the gold standard to differentiate these flaviviruses.

Towards the diagnosis of dengue virus and its serotypes using designed CRISPR/Cas13 gRNAs

Dengue Virus (DENV) is a mosquito-borne virus that is prevalent in the world's tropical and subtropical regions. Therefore, early detection and surveillance can help in the management of this disease. Current diagnostic methods rely primarily on ELISA, PCR, and RT-PCR, among others, which can only be performed in specialized laboratories and require sophisticated instruments and technical expertise. CRISPR-based technologies on the other hand have field-deployable viral diagnostics capabilities that could be used in the development of point-of-care molecular diagnostics. The first step in the field of CRISPR-based virus diagnosis is to design and screen gRNAs for high efficiency and specificity. In the present study, we employed a bioinformatics approach to design and screen DENV CRISPR/Cas13 gRNAs for conserved and serotype-specific variable genomic regions in the DENV genome. We identified one gRNA sequence specific for each of the lncRNA and NS5 regions and identified one gRNA against each of DENV1, DENV2, DENV3, and DENV4 to distinguish the four DENV serotypes. These CRISPR/Cas13 gRNA sequences will be useful in diagnosing the dengue virus and its serotypes for in vitro validation and diagnostics.

Integrated view of molecular diagnosis and prognosis of dengue viral infection: future prospect of exosomes biomarkers

Dengue viruses (DENVs) are the viruses responsible for dengue infection which affects lungs, liver, heart and also other organs of individuals. DENVs consist of the group of four serotypically diverse dengue viruses transmitted in tropical and sub-tropical countries of world. Aedes mosquito is the principal vector which spread the infection from infected person to healthy humans. DENVs can cause different syndromes depending on serotype of virus which range from undifferentiated mild fever to dengue hemorrhagic fever resulting in vascular leakage due to release of cytokine and Dengue shock syndrome with fluid loss and hypotensive shock, or other severe manifestations such as bleeding and organ failure. Increase in dengue cases in pediatric population is a major concern. Transmission of dengue depends on various factors like temperature, rainfall, and distribution of Aedes aegypti mosquitoes. The present review describes a comprehensive overview of dengue, pathophysiology, diagnosis, treatment with an emphasis on potential of exosomes as biomarkers for early prediction of dengue in pediatrics.

Zika Virus Non-Structural Protein 1 Antigen-Capture Immunoassay

Infection with Zika virus (ZIKV), a member of the Flavivirus genus of the Flaviviridae family, typically results in mild self-limited illness, but severe neurological disease occurs in a limited subset of patients. In contrast, serious outcomes commonly occur in pregnancy that affect the developing fetus, including microcephaly and other major birth defects. The genetic similarity of ZIKV to other widespread flaviviruses, such as dengue virus (DENV), presents a challenge to the development of specific ZIKV diagnostic assays. Nonstructural protein 1 (NS1) is established for use in immunodiagnostic assays for flaviviruses. To address the cross-reactivity of ZIKV NS1 with proteins from other flaviviruses we used site-directed mutagenesis to modify putative epitopes. Goat polyclonal antibodies to variant ZIKV NS1 were affinity-purified to remove antibodies binding to the closely related NS1 protein of DENV. An antigen-capture ELISA configured with the affinity-purified polyclonal antibody showed a linear dynamic range between approximately 500 and 30 ng/mL, with a limit of detection of between 1.95 and 7.8 ng/mL. NS1 proteins from DENV, yellow fever virus, St. Louis encephalitis virus and West Nile virus showed significantly reduced reactivity in the ZIKV antigen-capture ELISA. Refinement of approaches similar to those employed here could lead to development of ZIKV-specific immunoassays suitable for use in areas where infections with related flaviviruses are common.

Molecular techniques for the genomic viral RNA detection of West Nile, Dengue, Zika and Chikungunya arboviruses: a narrative review

Introduction: Molecular technology has played an important role in arboviruses diagnostics. PCR-based methods stand out in terms of sensitivity, specificity, cost, robustness, and accessibility, and especially the isothermal amplification (IA) method is ideal for field-adaptable diagnostics in resource-limited settings (RLS).Areas covered: In this review, we provide an overview of the various molecular methods for West Nile, Zika, Dengue and Chikungunya. We summarize literature works reporting the assessment and use of in house and commercial assays. We describe limitations and challenges in the usage of methods and opportunities for novel approaches such as NNext-GenerationSequencing (NGS).Expert opinion: The rapidity and accuracy of differential diagnosis is essential for a successful clinical management, particularly in co-circulation area of arboviruses. Several commercial diagnostic molecular assays are available, but many are not affordable by RLS and not usable as Point-of-care/Point-of-need (POC/PON) such as RReal-TimeRT-PCR, Array-based methods and NGS. In contrast, the IA-based system fits better for POC/PON but it is still not ideal for the multiplexing detection system. Improvement in the characterization and validation of current molecular assays is needed to optimize their translation to the point of care.

Rapid diagnostic tests for the detection of recent dengue infections: An evaluation of six kits on clinical specimens

Introduction

Early and rapid confirmation of dengue infections strengthens disease surveillance program and are critical to the success of vector control measures. Rapid diagnostics tests (RDTs) are increasingly used to confirm recent dengue infections due to their ease of use and short turnaround time for results. Several studies undertaken in dengue-endemic Southeast Asia have reported the performance of RDTs against enzyme-linked immunosorbent assay (ELISA), reverse transcriptase polymerase chain reaction (RT-PCR) and virus isolation methods. However, few studies have compared multiple RDTs for the detection of dengue NS1 antigen and IgM antibody in a single combo cassette. We evaluated six RDTs in Singapore for their utility in routine clinical testing to detect recent dengue infections.

Methods

The evaluation comprised two phases. The first phase sought to determine each RDT’s specificity to dengue NS1 and IgM using zika and chikungunya virus supernatant and zika convalescent samples. RDTs that cross-reacted with zika or chikungunya were not further tested in phase 2. The second phase sought to determine the sensitivity and specificity of the remaining RDTs to dengue NS1 and IgM using pre-characterised dengue specimens and non-dengue/chikungunya febrile clinical specimens.

Results

None of the RDTs cross-reacted with zika IgM in Phase 1. Truquick and Quickprofile cross reacted with zika and chikungunya viruses and were not evaluated thereafter. Standard Q had the highest dengue NS1 and IgM sensitivity at 87.0% and 84.3% respectively whereas Bioline (68.5%) and Multisure (58.3%) had the lowest dengue NS1 and IgM sensitivity respectively. Combining dengue NS1/IgM detection results greatly improved the RDT ability to detect recent dengue infection; Standard Q had the highest sensitivity at 99.1% while Multisure had the lowest at 92.6%. All the RDTs were highly specific for dengue NS1 and IgM (96.7% to 100%). All the RDTs had high positive predictive values (98.4% to 100%) for NS1, IgM and combined NS1/IgM parameters whereas Standard Q had the highest negative predictive values at 68.2% (NS1), 63.8% (IgM) and 96.8% (NS1/IgM). For the RDTs, detection of NS1 declined from acute to convalescent phase of illness whereas IgM detection rate gradually increased over time.

Conclusion

In our study, several RDTs were evaluated for their diagnostic accuracy and capability in detecting recent dengue infection. Standard Q demonstrated a high degree of diagnostic accuracy and capability in the detection of NS1 and IgM biomarkers. RDTs can provide rapid and accurate confirmation of recent dengue infections and augment dengue surveillance and control programmes. Further studies are required to assess the usefulness of these RDTs in other epidemiology settings.

A modified IgG avidity assay for reliability improvement of an in-house capture ELISA to discriminate primary from secondary dengue virus infections

Although discrimination between primary and secondary dengue infections can be performed using commercially available immunoassays or in-house tests, the evaluation of these methods is important, but is often problematic due to incomplete clinical data. In many cases, patients' sera submitted to the laboratory may not include the date of onset of illness which is necessary to discriminate primary and secondary dengue infections. This study reports improvement of an in-house capture ELISA using IgG avidity to discriminate primary and secondary dengue virus infection. Modified definition criteria were applied to characterize 99 single sera based on their IgM/IgG ratios. Regressive analysis indicated that the avidity test results (avidity index of 60 % as cutoff) for the discrimination showed good agreement (96 %) and a high correlation (r = -0.81) with those of the in-house capture ELISA (IgM/IgG ratio at 1.2 as cutoff). To further evaluate the in-house tests, 318 convalescent sera were compared with a Focus Diagnostics' anti-dengue IgM ELISA. Compared with the Focus Diagnostics system, the sensitivity of an in-house IgM determination was 83 %, whereas using both IgM and IgG capture ELISAs the sensitivity increased to 95 %.

Sero-epidemiological study on Dengue fever virus in humans and camels at Upper Egypt

BACKGROUND AND AIM

Dengue fever (DF) is an important mosquito-borne viral zoonosis affecting over 100 countries worldwide and putting about 3.9 billion people at risk of infection. The disease has re-emerged in Egypt since 2011; however, there is a paucity of recent epidemiological data available. Therefore, in this study, we employed a cross-sectional study to determine DF prevalence in humans and camels in Asyut and Sohag Governorates, Egypt, during 2019.

MATERIALS AND METHODS

A total of 91 humans and a similar number of dromedary camels were utilized in this study. Sera were obtained and analyzed for the presence of specific antibodies against DF virus using enzyme-linked immunosorbent assay. Related epidemiological data affecting the disease spread in humans and camels were recorded and statistically analyzed.

RESULTS

The seroprevalence of DF in humans and camels was 12.09% and 3.3%, respectively. The disease varied significantly by the species examined as humans were found to be at a higher risk of acquiring the infection compared to camels. Nearly equal odds of exposure (odds ratio [OR]) were seen in the individuals with close contact with camels compared to those without; however, individuals exposed to mosquitoes were at approximately 3 times higher risk of infection (OR=2.95 [95% confidence interval [CI], 0.73-11.93]) compared to individuals who were not exposed to mosquitoes (OR=0.033 [95% CI, 0.084-1.37]). Interestingly, DF seropositivity in camels was significantly related to the presence or absence of symptoms within 2 weeks before sampling (p=0.02) where symptomatic animals had higher odds of exposure (OR=19.51 [95%, 0.97-392.3]) compared to asymptomatic ones (OR=0.05 [95%, 0.002-1.03]).

CONCLUSION

The current study reports the presence of specific antibodies against dengue virus (DENV) in humans residing within Asyut and Sohag Governorates, Egypt. Furthermore, it provides the first serological evidence of DENV circulation in camels which is alarming. A more comprehensive study is needed; however, this baseline investigation underscores the urgent need for increasing awareness among people residing in the area as well as application of the appropriate mosquito control measures to avoid further spread of the disease.

A Comprehensive Study of Dengue Epidemics and Persistence of Anti-Dengue Virus Antibodies in District Swat, Pakistan

BACKGROUND

Dengue fever is one of the most common human arbovirus infections worldwide. In Pakistan, dengue initially became endemic in the big cities and then expanded to remote areas of the country. The current study reports the dengue epidemics, anti-DENV antibodies prevalence during the active and post-dengue infection, risk factors, disease symptoms, and spotting dengue infection densities in district Swat of Pakistan.

METHODS

Clinical signs and demographic data of dengue suspected individuals were collected at the time of screening through non-structural protein-1 antigen detection test during 2013-2015. Moreover, selected dengue confirmed individuals were screened for the presence of anti-dengue immunoglobulin (Ig) M and G during the active infection period and post-dengue infection.

RESULTS

A total of 8,770 individuals were infected with dengue in 2013 with 36 (0.41%) case fatalities, 307 in 2014 with no case fatality, and 13 in 2015 with no case fatality. The number of male and female cases were 6,139 and 2,631 in 2013, 183 and 124 in 2014, and only 10 and 3 in 2015, respectively. Among all the localities, Tehsil Babozai, an urban setting, reported the highest number of dengue patients during all the study years, that is, 7,673 (87.49% of the total cases) in 2013, 294 (95.76% of the total cases) in 2014, and 13 (100% cases) in 2015. Among 6 age groups, 21-30 years was found to be highly infected in 2013 (37.13% of all cases) and 2014 (33.55%). Furthermore, 1,231 (21.94% of all cases) had IgM antibodies and 71 (1.26%) had IgG antibodies in 2013, 78 (26% of all cases) had IgM antibodies and 7 (2.33%) had IgG antibodies in 2014, and only 4 (30.76%) patients had IgM and 0 (0%) had IgG antibodies in 2015. Furthermore, urban areas had the highest infection density in district Swat. The majority of the patients in rural areas had a traveling history to the urban areas before their illness.

CONCLUSION

To sum up, male gender, young individuals, and those living in urban areas were at the greater risk of dengue infection.

Rapid immunochromatographic tests for the diagnosis of dengue: a systematic review and meta-analysis

Dengue is an important arthropod-borne viral disease in terms of morbidity, mortality, economic impact and challenges in vector control. Benchmarks are expensive, time consuming and require trained personnel. Preventing dengue complications with rapid diagnosis has been based on the testing of easy-to-perform optimized immunochromatographic methods (ICT). This is a systematic meta-analysis review of the diagnostic accuracy of IgA, NS1, IgM and/or IgG ICT studies in suspected cases of acute or convalescent dengue, using a combination of RT-PCR, ELISA NS1, IgM IgG or viral isolation as a reference standard. This protocol was registered in PROSPERO (CRD42014009885). Two pairs of reviewers searched the PubMed, BIREME, Science Direct, Scopus, Web of Science, Ovid MEDLINE JBrigs, SCIRUS and EMBASE databases, selected, extracted, and quality-assessed by QUADAS 2. Of 3,783 studies, we selected 57, of which 40 in meta-analyses according to the analyte tested, with high heterogeneity (I2 > 90%), as expected for diagnostic tests. We detected higher pooled sensitivity in acute phase IgA (92.8%) with excellent (90%) specificity. ICT meta-analysis with NS1/IgM/IgG showed 91% sensitivity and 96% specificity. Poorer screening performance was for IgM/IgG ICT (sensitivity = 56%). Thus, the studies with NS1/IgM/IgG ICT showed the best combined performance in the acute phase of the disease.

Comparative specificity and sensitivity of NS1-based serological assays for the detection of flavivirus immune response

Flaviviruses are relevant animal and human pathogens of increasing importance worldwide. The similarities of the initial clinical symptoms and the serological cross-reactivity of viral structural antigens make a laboratory diagnosis of flavivirus infection problematic. The main aim of the present study was the comparative specificity and sensitivity analysis of the non-structural protein NS1 as an antigen to detect flavivirus antibodies in sera from exposed individuals. A strategy for the purification of native recombinant non-structural protein 1 of representative flaviviruses including tick-borne encephalitis, West Nile, Zika and dengue virus was developed. The immunological properties of the purified antigens were analyzed using sera of immunized mice and of infected individuals in comparison with standard commercial assays. Recombinant NS1 protein was confirmed as a valuable option for the detection of flavivirus antibodies with reduced cross-reactivity and high sensitivity offering additional advantages for the detection of vaccine breakthrough cases.

A cross sectional study of dengue virus infection in febrile patients presumptively diagnosed of malaria in Maiduguri and Jos plateau, Nigeria

Background

In Nigeria, where malaria is endemic, greater than 70% of febrile illnesses are treated presumptively as malaria, often without a laboratory evaluation for other possible causes of fever. This cross-sectional study evaluated the presence of dengue virus infection in febrile patients, presumptively diagnosed of malaria infections in the clinic.

Methodology

Blood samples were collected from 529 febrile patients (246 in Jos and 283 in Maiduguri) attending the general outpatient clinics of the Jos University Teaching Hospital (JUTH) and the University of Maiduguri Teaching Hospital (UMTH) and tested for anti-dengue immunoglobulin M (IgM) and immunoglobulin G (IgG), as well as anti-non-structural protein (NS1) by ELISA. The samples were also evaluated for presence of P. falciparum malaria parasites by microscopic examination of Giemsa-stained blood smears.

Results

The prevalence of confirmed, highly suggestive and probable dengue virus infections categorized in relation to duration of illness since onset of fever were 2.3%, 5.5% and 1.5% respectively, while the prevalence of anti-flavivirus IgG and IgM seropositivity was 11.7%. In a total of 117 (22.1%) patients (32 in Jos, 85 in Maiduguri), malaria parasites were detected by blood smear microscopy, out of which 7 (6%) also had a positively confirmed, highly suggestive or probable dengue test result.

Conclusion

Although the high cross-reactivity of anti-flavivirus antibodies should be taken into account in the interpretation of the seroprevalence data, our findings suggest a significant presence of dengue virus in this environment, some of which may otherwise be misdiagnosed as malaria. These findings are strong enough to recommend serological screening for anti-dengue virus titer and NS1 antigen for all febrile patients, as part of fever diagnostic protocols in tropical regions. Given the prevalence of dengue virus infections, there is also a need for a dengue control program and public education to prevent outbreaks and occurrence of severe dengue complications.

Selective Detection of Dengue Virus Serotypes Using Tandem Toehold-Mediated Displacement Reactions

Dengue virus (DENV) is the most common human arboviral infection worldwide and can present with severe clinical manifestations. Timely DENV detection improves clinical outcomes, and identification of the DENV serotype (DENV-1-4) may provide beneficial epidemiologic data to inform the initiation of control measures. Here, DENV RNA-triggered, enzyme-free tandem toehold-mediated displacement reactions were developed to identify and serotype DENV in RNA controls and contrived samples through the amplification of a fluorescent signal detected by the use of a fluorescent scanner and a confocal microscope. Each DENV serotype was detected selectively using both imaging methods. In addition, a 384-well plate was used to prepare an array for diagnosis of the four DENV RNA serotypes from contrived clinical samples. The four serotypes of dengue virus were detected using novel enzyme-free amplification reactions, which are more facile than amplification using reverse transcriptase PCR.

Sylvatic cycles of arboviruses in non-human primates

Arboviruses infecting people primarily exist in urban transmission cycles involving urban mosquitoes in densely populated tropical regions. For dengue, chikungunya, Zika and yellow fever viruses, sylvatic (forest) transmission cycles also exist in some regions and involve non-human primates and forest-dwelling mosquitoes. Here we review the investigation methods and available data on sylvatic cycles involving non-human primates and dengue, chikungunya, Zika and yellow fever viruses in Africa, dengue viruses in Asia and yellow fever virus in the Americas. We also present current putative data that Mayaro, o'nyong'nyong, Oropouche, Spondweni and Lumbo viruses exist in sylvatic cycles.

Evaluation of commercially available three dengue rapid diagnostic test kits for diagnosis of acute dengue virus infection at the point-of-care setting in Myanmar

Early and accurate diagnosis of dengue virus (DENV) infection is very important and Rapid Diagnostic Test (RDT) Kits are been used as a point-of-care test to check DENV infection. A Hospital and Laboratory-based descriptive study was conducted at 550-bedded Mandalay Children Hospital in 2018. Acute-phase serum samples were collected from 202 dengue suspected patients to evaluate the efficacy of RDT Kits for the diagnosis of DENV infection. Commercially available three test kits which include: ((i) CareUs Dengue Combo, Korea, (ii) Humasis Dengue Combo, Korea and (iii) Wondfo Dengue Combo, China) were validated against WHO-based reference standard tests. 140/202 patients (69.3%) was confirmed to have DENV infection. All four serotypes of dengue viruses (57 DENV-1, 7 DENV-2, 6 DENV-3 and 10 DENV-4) were identified from 80 dengue confirmed patients and DENV-1 was the dominant serotype. Combining the NS-1 antigen and IgM antibody results from the CareUs Dengue Combo Kit gave the best sensitivity (92.1%, 95% CI 86.4%-96.0%) and specificity (75.8%, 95%CI 63.3%-85.8%). Among the three RDT Kits, the performance of CareUS Kit was better than the other two. This study explored the evidence of the usefulness of RDT Kits at the point-of-care setting for diagnosis of acute dengue infection.

Role of Interleukin-10 and Abdominopelvic Ultrasound as a Potential Predictor of Disease Severity in Dengue Hemorrhagic Fever

Introduction

Dengue viral infections are a major cause of morbidity and mortality in tropical/subtropical countries. Early and prompt detection of dengue hemorrhagic fever (DHF), though challenging, is helpful to identify an individual that would benefit from intensive therapy.

Objective

The goal of this study was to determine the plasma interleukin-10 (IL-10) levels in DHF patients at four to seven days of disease onset and 24 hours after the first sample. We also aimed to determine the association of plasma IL-10 levels and abdominopelvic ultrasound findings.

Methods

A total of 50 registered DHF patients aged 15 to 50 years were recruited. Plasma IL-10 concentration measurements and abdominopelvic ultrasounds were performed. Patients were also categorized based on ultrasound grading I to IV (based on severity). Outcomes were described as recovery and shock. Platelet count and hematocrit percentages were also recorded.

Results

Plasma IL-10 levels were elevated in DHF patients and associated with fatal outcomes (p = 0.00). Binary regression-coefficient showed the direct effect of high levels of plasma IL-10 on the fatal outcome of patients 24 hours after the first sample (p = 0.04). Disease severity was predicted by a positive correlation between ultrasound grades and outcomes (p = 0.00). Spearman’s correlation coefficient found a highly significant inverse relationship between plasma IL-10 levels and platelet count after 24 hours (p = 0.01). However, a significant positive relationship was observed between elevated plasma IL-10 levels and hematocrit percentage after 24 hours (p = 0.01).

Conclusion

Elevated plasma IL-10 levels and abdominopelvic ultrasonography are promising potential predictors of disease progression and fatal outcome in DHF patients.

Diagnostic Performance of Dengue Virus Envelope Domain III in Acute Dengue Infection

Dengue, one of the most prevalent illnesses caused by dengue viruses that are members of the genus Flavivirus, is a significant global health problem. However, similar clinical symptoms and high antigenic homologies with other Flaviviruses in the endemic area pose difficulties for differential diagnosis of dengue from other arbovirus infections. Here, we investigated four types of recombinant envelope protein domain III (DV-rED III) derived from four dengue virus (DENV) serotypes for diagnostic potential in detecting IgM in acute phase (mainly 2–3 days after onset of fever). Each independent DV-1, -3, and -4-rED III-ELISA showed less than 60% sensitivity, but the combined results of DV-1, -3, and -4-rED III-ELISA led to sensitivity of 81.82% (18/22) (95% CI, 59.72 to 94.81) and 100% specificity (46/46) (95% CI, 92.29 to 100.00) as each antigen compensated the other antigen-derived negative result. In conclusion, the independent combination of data derived from each recombinant antigen (DV1-, DV3-, and DV4-rED III) showed comparable efficacy for the detection of IgM in patients with acute-phase dengue infection.

Electrochemical biosensing of mosquito-borne viral disease, dengue: A review

Dengue virus is a mosquito-borne, single positive-stranded RNA virus that spread human being through infected female Aedes mosquito bite and causes dengue fever. The demand for early detection of this virus has increased to control the widespread of infectious diseases and protect humankind from its harmful effects. Recently, biosensors are found to the potential tool to detect and quantify the virus with fast detection, relatively cost-effective, high sensitivity and selectivity than the conventional diagnostic methods such as immunological and molecular techniques. Mostly, the biosensors employ electrochemical detection technique with transducers, owing to its easy construction, low-cost, ease of use, and portability. Here, we review the current trends and advancement in the electrochemical diagnosis of dengue virus and discussed various types of electrochemical biosensing techniques such as; amperometric, potentiometric, impedometric, and voltammetric sensing. Apart from these, we discussed the role of biorecognition molecules such as nucleic acid, antibodies, and lectins in electrochemical sensing of dengue virus. In addition, the review highlighted the benefits of the electrochemical approach in comparison with traditional diagnostic methods. We expect that these dengue virus diagnostic techniques will continue to evolve and grow in future, with exciting new possibilities stemming from advancement in the rational design of electrochemical biosensors.

Biological evaluation of a series of benzothiazole derivatives as mosquitocidal agents

Aedes aegypti is associated with the transmission of numerous human and animal diseases, such as yellow fever, dengue fever, chikungunya, and more recently Zika virus. Emerging insecticide resistance has created a need to develop new mosquitocidal agents for effective control operations. A series of benzothiazole-piperidine derivatives (1-24) were investigated for their larvicidal and adulticidal effects on Ae. aegypti It was observed that compounds 2, 4, 6, 7, 8, 11 and 13 showed notable larvicidal activity. Furthermore, compounds 6 and 10 showed promising adulticidal activity. Based on the mosquitocidal properties of these compounds, docking studies were also carried out in the active site of the AeSCP2 enzyme to explore any insights into further in vitro enzyme studies. Docking results indicated that all these active compounds showed reasonable interactions with critical residues in the active site of this enzyme. This outcome suggested that these compounds might show their larvicidal and adulticidal effects via the inhibition of AeSCP2. According to in vitro and in silico studies, compounds 2, 4, 6, 7, 8, 10, 11 and 13 stand out as candidates for further studies.

A Mismatch-Tolerant Reverse Transcription Loop-Mediated Isothermal Amplification Method and Its Application on Simultaneous Detection of All Four Serotype of Dengue Viruses

Loop-mediated isothermal amplification (LAMP) has been widely used in the detection of pathogens causing infectious diseases. However, mismatches between primers (especially in the 3′-end) and templates significantly reduced the amplification efficiency of LAMP, and limited its application to genetically diverse viruses. Here, we reported a novel mismatch-tolerant LAMP assay and its application in the detection of dengue viruses (DENV). The novel method features the addition of as little as 0.15 U of high-fidelity DNA polymerase to the standard 25 μl LAMP reaction mixture. This amount was sufficient to remove the mismatched bases at the 3′-end of primers, thereby resulting in excellent tolerance for various mismatches occurring at the 3′-end of the LAMP primers during amplification. This novel LAMP assay has a markedly improved amplification efficiency especially for the mutants forming mismatches with internal primers (FIP/BIP) and loop primers (FLP/BLP). The reaction time of the novel method was about 5.6–22.6 min faster than the conventional LAMP method regardless of the presence or absence of mismatches between primers and templates. Using the novel method, we improved a previously established pan-serotype assay for DENV, and demonstrated greater sensitivity for detection of four DENV serotypes than the previous one. The limit of detection (LOD) of the novel assay was 74, 252, 78, and 35 virus RNA copies per reaction for DENV-1, DENV-2, DENV-3, and DENV-4, respectively. Among 153 clinical samples from patients with suspected DENV infection, the novel assay detected 94.8% samples being DENV positive, higher than that detected by the commercial NS1 antigen assay (92.2%), laboratory-based RT-PCR method (78.4%), and the conventional RT-LAMP assay (86.9%). Furthermore, the novel RT-LAMP assay has been developed into a visual determination method by adding colorimetric dyes. Because of its simplicity, all LAMP-based diagnostic assays may be easily updated to the newly improved version. The novel mismatch-tolerant LAMP method represents a simple, sensitive and promising approach for molecular diagnosis of highly variable viruses, and it is especially suited for application in resource-limited settings.

Definitive tests for dengue fever: when and which should I use?

Dengue is a mosquito-borne viral disease that has established itself globally in both endemic and epidemic transmission cycles. While diagnostic decision-making for dengue is often guided by clinical judgement, definitive laboratory tests, including rapid point-of-care tests, have many advantages in the primary care setting. These include providing epidemiological data and diagnostic clarity for atypical cases, as well as contributing to patient education and compliance. This article discussed the types of diagnostic methods for dengue, when to use them and the appropriateness of each test. Viral detection diagnostic methods such as NS1 antigen assays are generally used within the first week of illness onset, whereas dengue serology testing is most appropriate after that time frame. Locally available rapid point-of-care tests, which include both assays in one convenient test kit, can enhance dengue diagnosis in an endemic setting.

Dengue infection in India: A systematic review and meta-analysis

INTRODUCTION

Dengue is the most extensively spread mosquito-borne disease; endemic in more than 100 countries. Information about dengue disease burden, its prevalence, incidence and geographic distribution is critical in planning appropriate control measures against dengue fever. We conducted a systematic review and meta-analysis of dengue fever in India.

METHODS

We searched for studies published until 2017 reporting the incidence, the prevalence or case fatality of dengue in India. Our primary outcomes were (a) prevalence of laboratory confirmed dengue infection among clinically suspected patients, (b) seroprevalence in the general population and (c) case fatality ratio among laboratory confirmed dengue patients. We used binomial-normal mixed effects regression model to estimate the pooled proportion of dengue infections. Forest plots were used to display pooled estimates. The metafor package of R software was used to conduct meta-analysis.

RESULTS

Of the 2285 identified articles on dengue, we included 233 in the analysis wherein 180 reported prevalence of laboratory confirmed dengue infection, seven reported seroprevalence as evidenced by IgG or neutralizing antibodies against dengue and 77 reported case fatality. The overall estimate of the prevalence of laboratory confirmed dengue infection among clinically suspected patients was 38.3% (95% CI: 34.8%-41.8%). The pooled estimate of dengue seroprevalence in the general population and CFR among laboratory confirmed patients was 56.9% (95% CI: 37.5-74.4) and 2.6% (95% CI: 2-3.4) respectively. There was significant heterogeneity in reported outcomes (p-values<0.001).

CONCLUSIONS

Identified gaps in the understanding of dengue epidemiology in India emphasize the need to initiate community-based cohort studies representing different geographic regions to generate reliable estimates of age-specific incidence of dengue and studies to generate dengue seroprevalence data in the country.

Targeting vaccinations for the licensed dengue vaccine: Considerations for serosurvey design

BACKGROUND

The CYD-TDV vaccine was unusual in that the recommended target population for vaccination was originally defined not only by age, but also by transmission setting as defined by seroprevalence. WHO originally recommended countries consider vaccination against dengue with CYD-TDV vaccine in geographic settings only where prior infection with any dengue serotype, as measured by seroprevalence, was >170% in the target age group. Vaccine was not recommended in settings where seroprevalence was <50%. Test-and-vaccinate strategies suggested following new analysis by Sanofi will still require age-stratified seroprevalence surveys to optimise age-group targeting. Here we address considerations for serosurvey design in the context of vaccination program planning.

METHODS

To explore how the design of seroprevalence surveys affects estimates of transmission intensity, 100 age-specific seroprevalence surveys were simulated using a beta-binomial distribution and a simple catalytic model for different combinations of age-range, survey size, transmission setting, and test sensitivity/specificity. We then used a Metropolis-Hastings Markov Chain Monte-Carlo algorithm to estimate the force of infection from each simulated dataset.

RESULTS

Sampling from a wide age-range led to more accurate estimates than merely increasing sample size in a narrow age-range. This finding was consistent across all transmission settings. The optimum test sensitivity and specificity given an imperfect test differed by setting with high sensitivity being important in high transmission settings and high specificity important in low transmission settings.

CONCLUSIONS

When assessing vaccination suitability by seroprevalence surveys, countries should ensure an appropriate age-range is sampled, considering epidemiological evidence about the local burden of disease.

Validation of the Pockit Dengue Virus Reagent Set for Rapid Detection of Dengue Virus in Human Serum on a Field-Deployable PCR System

Dengue virus (DENV) infection, a mosquito-borne disease, is a major public health problem in tropical countries. Point-of-care DENV detection with good sensitivity and specificity enables timely early diagnosis of DENV infection, facilitating effective disease management and control, particularly in regions of low resources. The Pockit dengue virus reagent set (GeneReach Biotech), a reverse transcription insulated isothermal PCR (RT-iiPCR), is available to detect all four serotypes of DENV on the field-deployable Pockit system, which is ready for on-site applications. In this study, analytical and clinical performances of the assay were evaluated. The index assay did not react with 14 non-DENV human viruses, indicating good specificity. Compared to the U.S. CDC DENV-1-4 real-time quantitative RT-PCR (qRT-PCR) assay, testing with serial dilutions of virus-spiked human sera demonstrated that the index assay had detection endpoints that were separately comparable with the 4 serotypes. Excellent reproducibility was observed among repeat tests done by six operators at three sites. In clinical performance, 195 clinical sera collected around Kaohsiung city in 2012 and 21 DENV-4-spiked sera were tested with the RT-iiPCR and qRT-PCR assays in parallel. The 121 (11 DENV-1, 78 DENV-2, 11 DENV-3, and 21 DENV-4) qRT-PCR-positive and 95 qRT-PCR-negative samples were all positive and negative by the RT-iiPCR reagent results, respectively, demonstrating high (100%) interrater agreement (95% confidence interval [CI_95%], ∼98.81% to 100%; κ = 1). With analytical and clinical performance equivalent to those of the reference qRT-PCR assay, the index PCR assay on the field-deployable system can serve as a highly sensitive and specific on-site tool for DENV detection.

History, epidemiology and diagnostics of dengue in the American and Brazilian contexts: a review

Dengue virus (DENV), an arbovirus transmitted by mosquitoes, has become a major threat to American human life, reaching approximately 23 million cases from 1980 to 2017. Brazil is among the countries most affected by this terrible viral disease, with 13.6 million cases. DENV has four different serotypes, DENV1-4, which show a broad clinical spectrum. Dengue creates a staggering epidemiological and economic burden for endemic countries. Without a specific therapy and with a commercial vaccine that presents some problems relative to its full effectiveness, initiatives to improve vector control strategies, early disease diagnostics and the development of vaccines and antiviral drugs are priorities. In this study, we present the probable origins of dengue in America and the trajectories of its spread. Overall, dengue diagnostics are costly, making the monitoring of dengue epidemiology more difficult and affecting physicians' therapeutic decisions regarding dengue patients, especially in developing countries. This review also highlights some recent and important findings regarding dengue in Brazil and the Americas. We also summarize the existing DENV polymerase chain reaction (PCR) diagnostic tests to provide an improved reference since these tests are useful and accurate at discriminating DENV from other flaviviruses that co-circulate in the Americas. Additionally, these DENV PCR assays ensure virus serotyping, enabling epidemiologic monitoring.

Prolonged persistence of IgM against dengue virus detected by commonly used commercial assays

BACKGROUND

Initial symptoms of dengue fever are non-specific, and thus definite diagnosis requires laboratory confirmation. Detection of IgM against dengue virus (DENV) has become widely used for dengue diagnosis. Understanding the persistence of anti-DENV IgM in subjects after acute infection is essential in order to interpret test results correctly. Although the longevity of anti-DENV IgM has been vehemently investigated in symptomatic children, anti-DENV IgM persistence in adults and in asymptomatically infected people have seldom been reported.

METHODS

We prospectively investigated 44 adults with detectable anti-DENV IgM in a serosurvey conducted in the 2015 dengue epidemic in Tainan, Taiwan. Among subjects within the cohort, 17 were classified to be symptomatic and 27 were asymptomatic. The enzyme-linked immunosorbent assay (ELISA) from Standard Diagnostic (SD) and Focus Diagnostic were used to detect anti-DENV IgM for specimens collected initially, at 6 and 12 months. Regression analyses were used to estimate the duration of anti-DENV IgM fell below the detectable level. Rapid dengue tests from Standard Diagnostics had been widely adopted to detect anti-DENV IgM in Taiwan during the 2015 dengue outbreak. As such, collected specimens were also evaluated with the SD rapid dengue test in parallel.

RESULTS

Anti-DENV IgM was detectable in 70.5 and 46.2% of the 44 subjects at 6 months and 12 months by the SD ELISA, respectively, while 13.6 and 7.7%, respectively, by the Focus ELISA. There was no significant difference in anti-DENV IgM detection for the follow-up specimens between subjects with symptomatic and asymptomatic infections. The regression analysis estimated that anti-DENV IgM persistence fell to the undetectable level at 338.3 days (95% CI 279.7-446.9) by SD ELISA, while at 175.7 days (95% CI 121.9-221.1) by Focus ELISA. The detectable frequency of anti-DENV IgM by rapid tests was 86.4%, 68.2 and 35.9% at initial, 6 and 12 months, respectively.

CONCLUSION

Anti-DENV IgM was found to persist much longer than previously thought, suggesting a necessity of re-evaluation of the use of anti-DENV IgM for both the diagnosis of dengue and serological surveillance, especially when large outbreaks have occurred in the preceding year.

Dengue fever: Report from the task force on tropical diseases by the World Federation of Societies of Intensive and Critical Care Medicine

Dengue is an arbovirus affecting humans and spread by mosquitoes. Severe dengue follows a secondary infection with a different virus serotype. The problem is truly global as it is endemic in over 100 countries. Severe dengue can be a life-threatening because of increased vascular permeability, resulting in leakage of fluid from the intravascular compartment to the extravascular space. When major bleeding does occur, it is almost invariably combined with profound shock since this, in combination with thrombocytopenia, hypoxia, and acidosis, can lead to multiple organ failure and disseminated intravascular coagulation. Dengue hemorrhagic fever and dengue shock syndrome are among the leading causes of morbidity and mortality in patients suffering from Dengue. Commercial rapid tests and ELISA kits are freely available, ensuring early diagnosis. The basis of management of severe dengue is effective fluid replacement. Future directions in management will involve vector control and development of effective vaccination.

A novel indirect ELISA for diagnosis of dengue fever

Background & objectives:

Dengue fever (DF) is associated with significant morbidity and mortality in the tropical and sub-tropical regions of the world. Since there are no effective antiviral drugs for treatment, clinicians often rely on the accurate diagnosis of dengue fever to begin supportive therapy at early stages of the illness. The objective of this study was to develop an in-house dengue virus serotype 2 (DENV-2) non-structural protein- 5 (NS5) based indirect ELISA.

Methods:

DENV-2 was raised in Vero cells and the viral proteins were separated and subsequently the NS5 protein was eluted. Serum samples from primary and secondary dengue fever patients; and acute and convalescent samples from Japanese encephalitis (JE) and West Nile virus (WNV) cases were used to validate the ELISA.

Results:

The assay was found to be 100 per cent specific in detecting DENV-2 specific antibodies from patient's serum. However, in terms of sensitivity, the assay could detect IgM antibodies only from 90 per cent of the primary dengue samples. The IgM/IgG ratio of the primary and secondary samples was 7.24 and 0.64, respectively.

Interpretation & conclusions:

The results indicate that the DENV-2 NS5 ELISA is dengue group specific and can be used to differentiate dengue infection from other circulating Flavivirus infections. This NS5 ELISA can also be used to distinguish between primary and secondary dengue fever on the basis of IgM/IgG ratios. Further studies with larger sample sizes and different DENV serotypes are required to validate the ELISA.

The value of daily platelet counts for predicting dengue shock syndrome: Results from a prospective observational study of 2301 Vietnamese children with dengue

BACKGROUND

Dengue is the most important mosquito-borne viral infection to affect humans. Although it usually manifests as a self-limited febrile illness, complications may occur as the fever subsides. A systemic vascular leak syndrome that sometimes progresses to life-threatening hypovolaemic shock is the most serious complication seen in children, typically accompanied by haemoconcentration and thrombocytopenia. Robust evidence on risk factors, especially features present early in the illness course, for progression to dengue shock syndrome (DSS) is lacking. Moreover, the potential value of incorporating serial haematocrit and platelet measurements in prediction models has never been assessed.

METHODOLOGY/PRINCIPAL FINDINGS

We analyzed data from a prospective observational study of Vietnamese children aged 5-15 years admitted with clinically suspected dengue to the Hospital for Tropical Diseases in Ho Chi Minh City between 2001 and 2009. The analysis population comprised all children with laboratory-confirmed dengue enrolled between days 1-4 of illness. Logistic regression was the main statistical model for all univariate and multivariable analyses. The prognostic value of daily haematocrit levels and platelet counts were assessed using graphs and separate regression models fitted on each day of illness. Among the 2301 children included in the analysis, 143 (6%) progressed to DSS. Significant baseline risk factors for DSS included a history of vomiting, higher temperature, a palpable liver, and a lower platelet count. Prediction models that included serial daily platelet counts demonstrated better ability to discriminate patients who developed DSS from others, than models based on enrolment information only. However inclusion of daily haematocrit values did not improve prediction of DSS.

CONCLUSIONS/SIGNIFICANCE

Daily monitoring of platelet counts is important to help identify patients at high risk of DSS. Development of dynamic prediction models that incorporate signs, symptoms, and daily laboratory measurements, could improve DSS prediction and thereby reduce the burden on health services in endemic areas.

Evaluation and optimization of SYBR Green real-time reverse transcription polymerase chain reaction as a tool for diagnosis of the Flavivirus genus in Brazil

INTRODUCTION

The genus Flavivirus includes several pathogenic species that cause severe illness in humans. Therefore, a rapid and accurate molecular method for diagnosis and surveillance of these viruses would be of great importance. Here, we evaluate and optimize a quantitative real-time reverse transcription polymerase chain reaction (RT-PCR) method for the diagnosis of the Flavivirus genus.

METHODS

We evaluated different commercial kits that use the SYBR Green system for real-time RT-PCR with a primer set that amplifies a fragment of the NS5 flavivirus gene. The specificity and sensitivity of the assay were tested using twelve flaviviruses and ribonucleic acid (RNA) transcribed from the yellow fever virus. Additionally, this assay was evaluated using the sera of 410 patients from different regions of Brazil with acute febrile illness and a negative diagnosis for the dengue virus.

RESULTS

The real-time RT-PCR amplified all flaviviruses tested at a melting temperature of 79.92 to 83.49°C. A detection limit of 100 copies per ml was determined for this assay. Surprisingly, we detected dengue virus in 4.1% (17/410) of samples from patients with febrile illness and a supposedly negative dengue infection diagnosis. The viral load in patients ranged from 2.1×107to 3.4×103copies per ml.

CONCLUSIONS

The real-time RT-PCR method may be very useful for preliminary diagnoses in screenings, outbreaks, and other surveillance studies. Moreover, this assay can be easily applied to monitor viral activity and to measure viral load in pathogenesis studies.

Enhancing the sensitivity of Dengue virus serotype detection by RT-PCR among infected children in India

Dengue surveillance relies on reverse transcription-polymerase chain reaction (RT-PCR), for confirmation of dengue virus (DENV) serotypes. We compared efficacies of published and modified primer sets targeting envelope (Env) and capsid-premembrane (C-prM) genes for detection of circulating DENV serotypes in southern India. Acute samples from children with clinically-diagnosed dengue were used for RT-PCR testing. All samples were also subjected to dengue serology (NS1 antigen and anti-dengue-IgM/IgG rapid immunochromatographic assay). Nested RT-PCR was performed on viral RNA using three methods targeting 654bp C-prM, 511bp C-prM and 641bp Env regions, respectively. RT-PCR-positive samples were validated by population sequencing. Among 171 children with suspected dengue, 121 were dengue serology-positive and 50 were dengue serology-negative. Among 121 serology-positives, RT-PCR detected 91 (75.2%) by CprM654, 72 (59.5%) by CprM511, and 74 (61.1%) by Env641. Among 50 serology-negatives, 10 (20.0%) were detected by CprM654, 12 (24.0%) by CprM511, and 11 (22.0%) by Env641. Overall detection rate using three methods sequentially was 82.6% (100/121) among serology-positive and 40.0% (20/50) among serology-negative samples; 6.6% (8/120) had co-infection with multiple DENV serotypes. We conclude that detection of acute dengue was enhanced by a modified RT-PCR method targeting the 654bp C-prM region, and further improved by using all three methods sequentially.

CLINICAL MANIFESTATION APPROACH OF DENGUE VIRAL INFECTION

Currently by an estimated 50-100 million dengue fever cases per year in worldwide, 500.000 were in the form of a disease is heavyDengue Hemorraghic Fever (DHF) and Dengue Shock Syndrome (DSS). Survey serology in Indonesia show that DEN-1 and DEN-2 arethe dominant serotipe virus until the end of the 1980s but the recent shift has occurred epizoötic where viruses DEN-3 dominant. (DosSantos, 2004; Malavige, 2004; Stephenson, 2005). Dengue virus infection induces transient immune aberrant activation of CD4/CD8ratio inversion and cytokine overproduction, and infection of endothelial cells and hepatocytes causes apoptosis and dysfunction ofthese cells. The aberrant immune responses not only impaire the immune response to clear the virus, but also result in overproductionof cytokines that affect monocytes, endothelial cells, and hepatocytes. Dengue-virus-induced vasculopathy and coagulopathy must beinvolved in the pathogenesis of hemorrhage, and the unbalace between coagulation and fibrinolysis activation, and prolonged durationof shock increase the likelihood of severe hemorrhage in DHF/DSS. Capillary leakage is triggered by the dengue virus itself or byantibodies to its antigen. To date, there are no effective strategies to prevent the progression of DHF/DSS. The control of dengue willbe possible only after an efficient vaccine has been developed

Retrospective analysis of prognostic factors in dengue infected patients with intracranial bleed

BACKGROUND

Dengue is one of the most common mosquito-transmitted arboviral disease of tropical and a few subtropical areas in the world. It is estimated that approximately 100 million cases occur per year and approximately 2.5 billion people are at risk of developing dengue infection. Hemorrhagic complications causing encephalopathy are quite rare but fatal consequences of this deadly disease. This study was conducted to discuss the prognostic factors in the management of intracranial hemorrhage in dengue infected patients.

METHODS

This retrospective study was conducted in the neurosurgery department of our tertiary healthcare centre. Duration of the study was 1 year, and 18 patients who presented with intracranial bleed and required neurosurgical care were included in this study. All patients had deranged coagulation profile and were thrombocytopenic. All the patients were given platelet concentrates for correction of thrombocytopenia. Eight of these patients had deterioration in their neurological status, and 6 of them underwent surgery.

RESULTS

Out of 18 patients, 12 (66.66%) were managed conservatively, including one case of cervical extradural hemorrhage. Five patients who were conservatively managed died because they had deep-seated bleed and rapid deterioration. The remaining 7 patients who were managed conservatively improved well with few residual deficits. Six (33.33%) patients who underwent surgery had excellent outcome with one case of mortality.

CONCLUSION

Very high index of suspicion is required in dengue infected patients for neurological complications, especially during the convalescence period. Special attention should be given to those patients who have altered sensorium, and should not be misinterpreted as fever delirium or toxic encephalopathy. It requires immediate attention and further neurological investigation (including thorough clinical examination). Timely diagnosis using a computed tomography scan and early neurosurgical intervention after rapid correction of thrombocytopenia can save many lives.

A Luminex-based single DNA fragment amplification assay as a practical tool for detecting and serotyping dengue virus

Dengue is a mosquito-borne viral infection that can evolve from subclinical to severe forms of disease. Early recognition during initial primary and secondary infections correlates with a reduced case-fatality rate in susceptible groups. The aim of this study was to standardize a DNA hybridization assay based on the Luminex technology for detecting and serotyping dengue virus (DENV). Reference DENVs representing the four different serotypes were used as controls to standardize the test. For validation, 16 DENV isolates obtained from a reference laboratory were analyzed in a double-blind manner to validate the test. Sixty blood samples from patients suspected of having dengue fever were used to evaluate the methodology after the validation step, and the results were compared with the reference semi-nested RT-PCR. Additionally, five human samples of each Zika and Chikungunya confirmed patients were used for specificity analysis. The Luminex-based assay correctly identified all 16 DENV isolates. In the evaluation step, the results of the RT-PCR/Luminex assay showed a concordance of 86.7% with those of the semi-nested RT-PCR. None of other virus infection samples was amplified. This is the first description of a hybridization assay that can discriminate the four DENV serotypes using probes against a single DENV sequence. The results indicated that the RT-PCR/Luminex DENV assay designed and evaluated in this study is a valuable additional tool for the early and rapid detection and serotyping of DENV, which could, in the future, be applied to new targets such as the Zika and Chikungunya viruses.

Is Reactive Dengue NS1Antigen Test a Warning Call for Hospital Admissions?

INTRODUCTION

Dengue fever is a major public health problem worldwide. The 2011 revised World Health Organization (WHO) guidelines have emphasized on early diagnosis and intervention to reduce the case fatality rate due to dengue fever. Rapid diagnostic tests like NS1 antigen assays have improved the detection of cases in early clinical phase of illness but its role as a predictor of severe dengue infection is not very clear.

AIM

To evaluate the utility of NS1 Ag assay as an early diagnostic marker and predictor of severe dengue infection.

MATERIALS AND METHODS

All children (0-12 years of age) diagnosed and confirmed with dengue fever at a tertiary care hospital in Puducherry between 01(st) August 2012 and 31(st) July 2015 were reviewed retrospectively from hospital case records as per the revised WHO guidelines for dengue fever. The diagnosis was confirmed by NS1antigen-based ELISA test or dengue serology for IgM and IgG antibodies and the data were analysed using SPSS 16.0 statistical software. After collecting all the data, all the variables were summarised by descriptive statistics. Categorical variables were expressed as frequencies and percentages, and then analysed by the χ(2) test or fishers exact test, where appropriate. Significance was taken at p-value< 0.05.

RESULTS

Among the 261 confirmed cases of dengue fever non-severe dengue and severe dengue infection was seen in 60.9% and 39.1% respectively. The mean age of presentation was 6.9 years and M:F ratio was 1.2:1. NS1 Ag was positive in 217 cases (83.1%) and among them non-severe dengue and severe dengue was seen in 65.9% and 34.1% cases respectively. A total of 44 cases (16.9%) were negative for NS1 Ag assay and positive for IgM MAC ELISA and among them 16 children (36.4%) had non-severe dengue infection where as 28 children (63.6%) had severe dengue infection. Secondary infection with (MAC-ELISA IgG) was seen in 17 cases (6.5%). NS1Ag assay was predominantly positive in acute phase sera, where as IgM/IgG MAC ELISA was predominantly positive in convalescent phase sera. There were six deaths (2.3%) and the common causes of poor outcome were multiorgan failure, encephalopathy and refractory shock.

CONCLUSION

NS1 Ag assay is a useful early diagnostic marker for dengue fever but cannot be used as an early predictor of severe dengue infection. The criteria for admission in hospitals of cases of dengue fever should be based on clinical warning signs rather than positive NS1 Antigen test.