Evaluation of the performances of six commercial kits designed for dengue NS1 and anti-dengue IgM, IgG and IgA detection in urine and saliva clinical specimens

Urinary dengue NS1 detection on Au-decorated ZnO nanowire platform

Biodetection for non-invasive diagnostics of fluids, especially urine, remains a challenge to scientists due to low target concentrations. And biological complexes of the detection target may contain contaminants that also interfere with any assay. Dengue non-structural 1 protein (Dengue NS1) is an important biomarker for dengue hemorrhagic fever and dengue shock syndrome. Here, we developed an Au-decorated nanowire platform and applied it with a sandwich fluorophore-linked immunosorbent well plate assay (FLISA) to detect Dengue NS1 in urine. For the platform, we fabricated zinc oxide (ZnO) nanowires to provide a high surface area and then coated them with gold nanoparticles (ZnO/Au nanowires) to simply modify the Dengue NS1 antibody and enhance the fluorescence intensity. Our platform employs a sandwich FLISA that exhibits high sensitivity, specifically detecting Dengue NS1 with a limit of detection (LOD) of 1.35 pg/mL. This LOD was 4500-fold lower than the LOD of a commercially available kit for Dengue NS1 enzyme-linked immunosorbent assay. We believe that our ZnO/Au nanowire platform has the potential to revolutionize the field of non-invasive diagnostics for dengue.

Diagnostic performance of the bioline dengue duo rapid test on symptomatic patients assisted at Armed Forces Hospital (Hfa) in Brasília, Brazil

Dengue necessitates accurate diagnosis. Rapid tests such as Bioline™ DENGUE DUO have gained traction, but validation in specific populations is essential. This study aimed to evaluate the performance of the Bioline™ test, alongside assessing the socio-epidemiological profile of symptomatic patients in a Brasília Military Hospital. The serum of 404 symptomatic patients was analyzed by the Bioline™ DENGUE DUO test, followed by Dengue virus detection and discrimination of the four serotypes by RT-qPCR. Accuracy was assessed using parameters including sensitivity (S), specificity (E), positive and negative predictive values (PPV and NPV), and positive (RV +) and negative (RV-) likelihood ratios. The NS1 component exhibited a sensitivity of 70.37%, a specificity of 97.30%, and an overall efficiency of 90.10% when compared to RT-qPCR as the gold standard. The IgM component demonstrated a sensitivity of 26.85%, a specificity of 89.53%, and an overall efficiency of 72.77% when compared to RT-qPCR as the gold standard. The IgG component demonstrated a sensitivity of 23.15%, a specificity of 68.92%, and an overall efficiency of 56.68% when compared to RT-qPCR as the gold standard. Several rapid tests are commercially available. However, considering variations across regions and demographic groups, it is important to question their accuracy in specific populations. Rapid tests are important screening tools, but they can have limitations for the certainty of diagnosis. Bioline™ DENGUE DUO displayed good specificity, but sensitivity was slightly below optimal levels. While helpful for confirming dengue, improvements are needed to effectively rule out the disease.

The Role of NS1 Protein in the Diagnosis of Flavivirus Infections

Nonstructural protein 1 (NS1) is a glycoprotein among the flavivirus genus. It is found in both membrane-associated and soluble secreted forms, has an essential role in viral replication, and modulates the host immune response. NS1 is secreted from infected cells within hours after viral infection, and thus immunodetection of NS1 can be used for early serum diagnosis of dengue fever infections instead of real-time (RT)-PCR. This method is fast, simple, and affordable, and its availability could provide an easy point-of-care testing solution for developing countries. Early studies show that detecting NS1 in cerebrospinal fluid (CSF) samples is possible and can improve the surveillance of patients with dengue-associated neurological diseases. NS1 can be detected postmortem in tissue specimens. It can also be identified using noninvasive methods in urine, saliva, and dried blood spots, extending the availability and effective detection period. Recently, an enzyme-linked immunosorbent assay (ELISA) assay for detecting antibodies directed against Zika virus NS1 has been developed and used for diagnosing Zika infection. This NS1-based assay was significantly more specific than envelope protein-based assays, suggesting that similar assays might be more specific for other flaviviruses as well. This review summarizes the knowledge on flaviviruses' NS1's potential role in antigen and antibody diagnosis.

Efficacy Assessment of Autodissemination Using Pyriproxyfen-Treated Ovitraps in the Reduction of Dengue Incidence in Parañaque City, Philippines: A Spatial Analysis

Dengue is one of the most important vector-borne diseases worldwide and is a significant public health problem in the tropics. Mosquito control continues to be the primary approach to reducing the disease burden and spread of dengue virus (DENV). Aside from the traditional larviciding and adulticiding interventions, autodissemination using pyriproxyfen-treated (AD-PPF) ovitraps is one of the promising methods to complement existing vector control strategies. Our paper assessed the efficacy of AD-PPF in reducing DENV infections in two barangays in Parañaque City. Using saliva samples from the participants from both the control and intervention sites, we collected the seroprevalence data for three months in each of the two years. Spatial analysis was conducted to determine hotspot areas and identify DENV infection distributions across the trial periods. The results showed that the intervention site was identified as having a clustering of DENV infections in Month 0 of Year 1 and shifted to a random dispersion of dengue cases at the end of Month 3 in Year 2. The disappearance of the clustering of the intervention site translates to a decrease in the cases of DENV infection relative to the control site. Furthermore, we also identified that DENV transmission occurred at a small-scale level that did not go beyond 86 m. In conclusion, AD-PPF is suggested to be an effective strategy and may be used as an additional vector control approach, albeit based on this short-term implementation.

Spin-Enhanced Lateral Flow Immunoassay for High-Sensitivity Detection of Nonstructural Protein NS1 Serotypes of the Dengue Virus

Dengue fever is a global mosquito-borne viral infectious disease that has, in recent years, rapidly spread to almost all regions of the world. Lack of vaccination and directed treatment makes detection at the infection's early stages extremely important for disease prevention and clinical care. In this paper, we developed a rapid and highly sensitive dengue detection tool using a novel platform of diagnosis, called spin-enhanced lateral flow immunoassay (SELFIA) with a fluorescent nanodiamond (FND) as a reporter. Taking advantage of the unique magneto-optical properties of negatively charged nitrogen-vacancy centers in the FND, the SELFIA platform utilizes alternating electromagnetic fields to modulate signals from FND's fluorescence to provide sensitive and specific results. With sandwich SELFIA, we could efficiently detect all four dengue non-structural protein (NS1) serotypes (DV1, DV2, DV3, and DV4). The lowest detection concentration of the dengue NS1 antigens varied from 0.1 to 1.3 ng/mL, which is among the lowest limits of detection to date. The FND-based SELFIA technique is up to 500 and 5000 times more sensitive than carbon black and conventional gold nanoparticles, respectively. By using different anti-NS1 antibodies, we could differentiate the NS1 antigen serotypes contained in the tested samples via three simultaneous assays. Proposed SELFIA allows for both qualitative and quantitative differentiation between different NS1 protein serotypes, which will assist in the development of a highly sensitive and specific detection platform for dengue screening that has the potential to detect the disease at its early stages, especially in high-risk and limited-resource areas.

Smartphone multiplex microcapillary diagnostics using Cygnus: Development and evaluation of rapid serotype-specific NS1 detection with dengue patient samples

Laboratory diagnosis of dengue virus (DENV) infection including DENV serotyping requires skilled labor and well-equipped settings. DENV NS1 lateral flow rapid test (LFT) provides simplicity but lacks ability to identify serotype. A simple, economical, point-of-care device for serotyping is still needed. We present a gravity driven, smartphone compatible, microfluidic device using microcapillary film (MCF) to perform multiplex serotype-specific immunoassay detection of dengue virus NS1. A novel device–termed Cygnus–with a stackable design allows analysis of 1 to 12 samples in parallel in 40 minutes. A sandwich enzyme immunoassay was developed to specifically detect NS1 of all four DENV serotypes in one 60-μl plasma sample. This test aims to bridge the gap between rapid LFT and laboratory microplate ELISAs in terms of sensitivity, usability, accessibility and speed. The Cygnus NS1 assay was evaluated with retrospective undiluted plasma samples from 205 DENV infected patients alongside 50 febrile illness negative controls. Against the gold standard RT-PCR, clinical sensitivity for Cygnus was 82% in overall (with 78, 78, 80 and 76% for DENV1-4, respectively), comparable to an in-house serotyping NS1 microplate ELISA (82% vs 83%) but superior to commercial NS1-LFT (82% vs 74%). Specificity of the Cygnus device was 86%, lower than that of NS1-microplate ELISA and NS1-LFT (100% and 98%, respectively). For Cygnus positive samples, identification of DENV serotypes DENV2-4 matched those by RT-PCR by 100%, but for DENV1 capillaries false positives were seen, suggesting an improved DENV1 capture antibody is needed to increase specificity. Overall performance of Cygnus showed substantial agreement to NS1-microplate ELISA (κ = 0.68, 95%CI 0.58–0.77) and NS1-LFT (κ = 0.71, 95%CI 0.63–0.80). Although further refinement for DENV-1 NS1 detection is needed, the advantages of multiplexing and rapid processing time, this Cygnus device could deliver point-of-care NS1 antigen testing including serotyping for timely DENV diagnosis for epidemic surveillance and outbreak prediction.

Diagnosis of the important mosquito-transmitted dengue virus (DENV) requires laboratory assays to detect viral genome (RT-PCR), viral NS1 protein (immunoassay) or DENV specific antibodies. Current point-of-care NS1 tests cannot distinguish serotype, so laboratory tests are still essential to determine which of 4 DENV serotypes is present. Here we present a rapid serotype-specific NS1 test in a portable microfluidic format. Ten parallel 0.2 mm tubes inside a flat plastic ribbon perform multiplex NS1 immunoassays. A simple cassette delivers sample and reagents sequentially through the microcapillaries by gravity. By stacking cassettes, 12 tests could be performed in under 40 minutes, with results recorded by smartphone. When evaluated with 205 patients plus 50 control samples, and results compared to conventional RT-PCR, the sensitivity for DENV1 to 4 was 78%, 78%, 80%, and 76%, respectively, with specificity of 100% for DENV2-4. DENV1 showed some false positives due to cross-reactivity of the capture antibody. Serotyping performance with MCF-Cygnus devices showed substantial agreement to the serotyping-NS1 microplate ELISA. Therefore, these simple and portable microcapillary immunoassay devices could support dengue NS1 serotyping with potential benefits for near-patient diagnosis, real-time epidemic surveillance and outbreak mapping.

Assessing Entomological and Epidemiological Efficacy of Pyriproxyfen-Treated Ovitraps in the Reduction of Aedes Species: A Quasi-Experiment on Dengue Infection Using Saliva Samples

Our study assessed the impact of using ovitraps with pyriproxyfen on mosquito populations and the feasibility of using human saliva samples to test for seroconversion to dengue virus (DENV). We used a quasi-experimental research design by forming the intervention (n = 220) and the control (n = 223) groups in neighboring Taguig City, Philippines, over 4 months. Socio-demographic data, entomological indices, and IgG antibodies against DENV were measured. Associations between the implementation of ovitraps dosed with pyriproxyfen and mosquito densities (percentage positive ovitraps and container indices) and DENV seroconversion were calculated post-intervention in Months 2, 3, and 4. Among the participants recruited at baseline, 17 and 13 were seropositive for dengue (DENV) in the intervention and control groups, respectively. Both entomological indices were lower in the treated area than the control site at post-intervention Months 2, 3, and 4, but not earlier. Dengue seroconversions rates decreased in the treated population, but not significantly so. In conclusion, the use of PPF-treated ovitraps may have impacted the mosquito population, but not seroconversion rates. Compliance in providing saliva samples and the ability to detect IgG antibodies within these samples was encouraging and suggests that further studies on larger populations for longer durations are warranted.

Urinary immunoglobulins in viral diagnosis: An overview

Antibody detection by serological methods gained a lot of interest in recent years and has become the backbone of virological diagnosis. Despite the detection of all five classes of immunoglobulins in urine, not much attention has been paid to the use of urine as a diagnostic sample to detect viral antibodies. Unlike venipuncture, this non-invasive mode of sample collection can help cover all age groups, especially paediatric and old age patients, where blood collection is difficult. Using urine as a sample is also economical and involves lesser risk in sample collection. The antibodies are found to be stable in urine at room temperature for a prolonged period, which makes the sample transport management easier as well. A few recent studies, have also shown that the detection limit of antibodies in urine is at par with serum or other clinical material. So, the ease in sample collection, availability of samples in large quantity and stability of immunoglobulins in urine for prolonged periods can make urine an ideal sample for viral diagnosis.

Aspects of Point-of-Care Diagnostics for Personalized Health Wellness

Advancements in analytical diagnostic systems for point-of-care (POC) application have gained considerable attention because of their rapid operation at the site required to manage severe diseases, even in a personalized manner. The POC diagnostic devices offer easy operation, fast analytical outcome, and affordable cost, which promote their advanced research and versatile adoptability. Keeping advantages in view, considerable efforts are being made to design and develop smart sensing components such as miniaturized transduction, interdigitated electrodes-based sensing chips, selective detection at low level, portable packaging, and sustainable durability to promote POC diagnostics according to the needs of patient care. Such effective diagnostics systems are in demand, which creates the challenge to make them more efficient in every aspect to generate a desired bio-informatic needed for better health access and management. Keeping advantages and scope in view, this mini review focuses on practical scenarios associated with miniaturized analytical diagnostic devices at POC application for targeted disease diagnostics smartly and efficiently. Moreover, advancements in technologies, such as smartphone-based operation, paper-based sensing assays, and lab-on-a-chip (LOC) which made POC more sensitive, informative, and suitable for major infectious disease diagnosis, are the main focus here. Besides, POC diagnostics based on automated patient sample integration with a sensing platform is continuously improving therapeutics interventions against specific infectious disease. This review also discussed challenges associated with state-of-the-art technology along with future research opportunities to design and develop next generation POC diagnostic systems needed to manage infectious diseases in a personalized manner.

Evaluation of immunoglobulin M-specific capture enzyme-linked immunosorbent assays and commercial tests for flaviviruses diagnosis by a National Reference Laboratory

Zika and Dengue viruses present considerable immunological cross-reactivity, resulting in a troublesome serodiagnosis due to occurrence of false positive results. Due to Brazil's wide variety of circulating flaviviruses we aimed to access the use of in house serological tests adapted by National Reference Laboratory for Arboviruses in Brazil and evaluate commercial tests available. We evaluated in house IgM ELISAs for the individual detection of anti-ZIKV, -DENV, and -YFV IgM, against a panel of samples positive for dengue, zika, yellow fever, Rocio, Ilheus, Saint Louis encephalitis, West Nile and chikungunya. We also evaluated two commercial kits for dengue and zika IgM detection recommended by the Brazilian Ministry of Health in 2015. The sensitivity and specificity for the in house ZIKV IgM ELISA was 60.0 % and 88.6 % and for the in house DENV IgM ELISA was 100 % and 82.2 %, respectively. The in house YFV IgM ELISA presented 100 % for both sensitivity and specificity. The Novagnost Zika Virus IgM test presented a sensitivity of 47.3 % and specificity of 85.3 % and the Serion ELISA classic Dengue Virus IgM, 92.8 % and 58.9 %, respectively. Overall, both in house ELISAs for ZIKV and DENV adapted and evaluated here, presented better performances than the commercial kits tested.

Label-Free Electrochemical Biosensors for the Determination of Flaviviruses: Dengue, Zika, and Japanese Encephalitis

A highly effective way to improve prognosis of viral infectious diseases and to determine the outcome of infection is early, fast, simple, and efficient diagnosis of viral pathogens in biological fluids. Among a wide range of viral pathogens, Flaviviruses attract a special attention. Flavivirus genus includes more than 70 viruses, the most familiar being dengue virus (DENV), Zika virus (ZIKV), and Japanese encephalitis virus (JEV). Haemorrhagic and encephalitis diseases are the most common severe consequences of flaviviral infection. Currently, increasing attention is being paid to the development of electrochemical immunological methods for the determination of Flaviviruses. This review critically compares and evaluates recent research progress in electrochemical biosensing of DENV, ZIKV, and JEV without labelling. Specific attention is paid to comparison of detection strategies, electrode materials, and analytical characteristics. The potential of so far developed biosensors is discussed together with an outlook for further development in this field.

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.

ELISA Saliva for Trypanosoma cruzi Antibody Detection: An Alternative for Serological Surveys in Endemic Regions

Chagas is a neglected disease endemic in Latin America. Vector transmission control had been aggressively performed. Recent entomological surveillance in Brazil has revealed natural infection rates ranging from 0.40% to 0.52%. Although serological surveys are complex to develop, they are important for disease control. In this study, we validated the use of saliva in ELISA commercial kits with a cohort of 100 patients with Chagas disease followed at Hospital das Clinicas in São Paulo, Brazil, and 50 healthy controls. Five ELISA kits for detecting antibodies against Trypanosoma cruzi were tested. The best discrimination between Chagas patients and controls was observed with the Wiener kit, which yielded a sensitivity of 97% and a specificity of 100%. Our findings reveal that the use of saliva may be an alternative to large-scale screening surveys in detecting T. cruzi antibodies; it is a noninvasive sample collection method potentially key to large-scale screening in children.

Profiling of flaviviral NS2B-NS3 protease specificity provides a structural basis for the development of selective chemical tools that differentiate Dengue from Zika and West Nile viruses

West Nile virus (WNV) and Dengue virus (DENV) are mosquito-borne pathogenic flaviviruses. The NS2B-NS3 proteases found in these viruses are responsible for polyprotein processing and are therefore considered promising medical targets. Another ortholog of these proteases is found in Zika virus (ZIKV). In this work, we applied a combinatorial chemistry approach - Hybrid Combinatorial Substrate Library (HyCoSuL), to compare the substrate specificity profile at the P4-P1 positions of the NS2B-NS3 proteases found in all three viruses. The obtained data demonstrate that Zika and West Nile virus NS2B-NS3 proteases display highly overlapping substrate specificity in all binding pockets, while the Dengue ortholog has slightly different preferences toward natural and unnatural amino acids at the P2 and P4 positions. We used this information to extract specific peptide sequences recognized by the Dengue NS2B-NS3 protease. Next, we applied this knowledge to design a selective substrate and activity-based probe for the Dengue NS2B-NS3 protease. Our work provides a structural framework for the design of inhibitors, which could be used as a lead structure for drug development efforts.

The detection of anti-dengue virus IgM in urine in participants enrolled in an acute febrile illness study in Puerto Rico

BACKGROUND

Dengue is an important arboviral disease with about 100 million dengue cases per year, of which, ~5% result in severe disease. Clinical differentiation of dengue from other acute febrile illnesses (AFI) is difficult, and diagnostic blood tests are costly. We evaluated the utility of anti-DENV IgM in urine to identify dengue cases among AFI patients enrolled in a clinical study.

METHODS

Between May 2012-March 2013, 1538 study participants with fever for ≤7 days were enrolled, a medical history was obtained, and serum and urine specimens were collected. Serum was tested for DENV RNA and anti-DENV IgM. Urine was tested for anti-DENV IgM, and its sensitivity and specificity to detect sera laboratory-positive dengue cases were calculated. We evaluated if urine anti-DENV IgM positivity early (≤5 days post-illness onset [DPO]) and late (6-14 DPO) in the clinical course was associated with dengue severity.

RESULTS

Urine anti-DENV IgM sensitivity and specificity were 47.4% and 98.5%, respectively, when compared with serum anti-DENV IgM ELISA results, and 29.7% and 91.1% when compared with serum rRT-PCR results. There was no correlation between urine anti-DENV IgM positivity and patient sex or pre-existing chronic disease. Early in the clinical course, a significantly higher proportion of those who developed dengue with warning signs had anti-DENV IgM in their urine when compared to those without warning signs (20.4% vs. 4.3%). There was no difference in the proportion with urine anti-DENV IgM positivity between severity groups late in the clinical course.

CONCLUSION

While detection of urine anti-DENV IgM lacked adequate diagnostic sensitivity, it is a highly specific marker for laboratory-positive dengue, and its presence early in the clinical course may distinguish those with more severe disease. Further assessment of urine anti-DENV IgM by DPO is warranted to determine its utility as an early diagnostic (and possibly prognostic) marker for dengue.

Comparison of Six Commercial Diagnostic Tests for the Detection of Dengue Virus Non-Structural-1 Antigen and IgM/IgG Antibodies

ELISAs and rapid diagnostic tests (RDTs) are widely used for diagnosing dengue virus (DENV) infection. Using 138 single blood samples, we compared the ability to detect non-structural (NS)-1 antigen and anti-DENV IgM/IgG antibodies among (1) DENV Detect NS1 ELISA, DENV Detect IgM capture ELISA and DENV Detect IgG ELISA (InBios International, Inc.); (2) Anti-Dengue virus IgM Human ELISA and Anti-Dengue virus IgG Human ELISA (Abcam); (3) Dengue virus NS1 ELISA, Anti-Dengue virus ELISA (IgM) and Anti-Dengue virus ELISA (IgG) (Euroimmun); (4) Asan Easy Test Dengue NS1 Ag 100 and Asan Easy Test Dengue IgG/IgM (Asan Pharm); (5) SD BIOLINE Dengue Duo (Standard Diagnostics); and (6) Ichroma Dengue NS1 and Ichroma Dengue IgG/IgM (Boditech Med). For NS1 antigen detection, InBios and Euroimmun showed higher sensitivities (100%) than the RDTs (42.9–64.3%). All tests demonstrated variable sensitivities for IgM (38.1–90.5%) and IgG (65.7–100.0%). InBios and Boditech Med demonstrated higher sensitivity (95.6% and 88.2%, respectively) than the other tests for combined NS1 antigen and IgM antibody. Five NS1 antigen tests had good agreement (92.8–98.6%) without showing positivity for chikungunya. However, all IgG tests demonstrated potential false-positivity with variable ranges. Clinical laboratories should note performance variations across tests and potential cross-reactivity.

Projected costs associated with school-based screening to inform deployment of Dengvaxia: Vietnam as a case study

Background

After new analysis, Sanofi Pasteur now recommends their dengue vaccine (Dengvaxia) should only be given to individuals previously infected with dengue and the World Health Organization's recommendations regarding its use are currently being revised. As a result, the potential costs of performing large-scale individual dengue screening and/or dengue serosurveys have become an important consideration for decision making by policymakers in dengue-endemic areas.

Methods

We used an ingredients-based approach to estimate the financial costs for conducting both a school-based dengue serosurvey and school-based individual dengue screening within a typical province in Vietnam, using an existing commercial indirect immunoglobulin G enzyme-linked immunosorbent assay kit. This costing is hypothetical and based on estimates regarding the resources that would be required to perform such activities.

Results

We estimated that performing a school-based individual screening of 9-year-olds would cost US$9.25 per child tested or US$197,827 in total for a typical province. We also estimated that a school-based serosurvey would cost US$10,074, assuming one class from each of the grades that include 8- to 11-year-olds are sampled at each of the 12 selected schools across the province.

Conclusions

The study indicates that using this vaccine safely on a large-scale will incur noteworthy operational costs. It is crucial that these be considered in future cost-effectiveness analyses informing how and where the vaccine is deployed.

A cross-sectional study of acute dengue infection in paediatric clinics in Cameroon

BACKGROUND

Dengue fever is the world's fastest spreading mosquito borne viral infection. It is prevalent throughout both subtropical and tropical region, and affects over 128 countries. Dengue virus (DENV) infection poses a serious global public health challenge to three billion people, resulting in approximately 200 million cases of morbidity and 50,000 cases of mortality annually. In Cameroon like in most sub-Saharan African countries, DENV infection occur concurrently with other infectious diseases whose symptoms often overlap, rendering differential diagnosis challenging. This study aims at determining the frequency of acute dengue among febrile children under 15 years attending hospitals in some areas of Cameroon.

METHODS

A total of 961 children under the age of 15 were recruited in a cross-sectional study using systematic sampling technique and by selecting each subject out of the three. The study was conducted in 10 public health centers in Cameroon. Demographic data and risk factors of the subjects were obtained using well-structured questionnaires. Dengue virus NS1 antigen, IgM and IgG were analysed using a Tell me fast® Combo Dengue NS1-IgG/IgM Rapid Test. An in-house ELISA test for dengue specific IgM antibody was equally performed for confirmation. Descriptive statistical analysis was performed using Graph pad version 6.0.

RESULTS

A prevalence of 6.14% acute dengue virus infection was observed among children with febrile illness with a significant difference (p = 0.0488) between males (4.7%) and females (7.7%). In addition, children who reportedly were unprotected from vectors, showed a comparatively higher prevalence of the disease seropositivity than those practicing protective measures.

CONCLUSION

DENV infection therefore is an important cause of fever among children in Cameroon. Thus, there is a need to include differential screening for DENV infections as a tool in the management of fever in children in the country.

Asymptomatic Dengue Virus Infections, Cambodia, 2012-2013

We investigated dengue virus (DENV) and asymptomatic DENV infections in rural villages of Kampong Cham Province, Cambodia, during 2012 and 2013. We conducted perifocal investigations in and around households for 149 DENV index cases identified through hospital and village surveillance. We tested participants 0.5-30 years of age by using nonstructural 1 rapid tests and confirmed DENV infections using quantitative reverse transcription PCR or nonstructural 1-capture ELISA. We used multivariable Poisson regressions to explore links between participants' DENV infection status and household characteristics. Of 7,960 study participants, 346 (4.4%) were infected with DENV, among whom 302 (87.3%) were <15 years of age and 225 (65.0%) were <9 years of age. We identified 26 (7.5%) participants with strictly asymptomatic DENV infection at diagnosis and during follow-up. We linked symptomatic DENV infection status to familial relationships with index cases. During the 2-year study, we saw fewer asymptomatic DENV infections than expected based on the literature.

Efficacy of the In2Care® auto-dissemination device for reducing dengue transmission: study protocol for a parallel, two-armed cluster randomised trial in the Philippines

Background

Mosquito-borne viruses are imposing an ever increasing health burden worldwide. In addition to the recent Zika and chikungunya virus epidemics, dengue viruses have become the fastest growing problem with a 40-fold increase in the number of reported cases over the past five decades. Current mosquito control techniques involving larval source reduction, larviciding, and space spray of adulticides are costly, laborious, and of debatable efficacy. There remains an urgent need for the development of intervention methods that can be reasonably implemented in the context of modern day urbanisation. Auto-dissemination (AD) of insecticide by adult mosquitoes offers a potentially practical and useful tool in an integrated vector control programme. Recently, an immediately employable AD device, the In2Care® mosquito trap, has been commercialised and shows promise as an effective tool. However, there remains a lack of demonstration of epidemiological efficacy.

Methods/design

This trial aims to assess the extent to which implementation of In2Care® mosquito traps can reduce vector Aedes (Stegomyia) spp. adult mosquito densities and dengue virus transmission as measured by sequential sero-conversion rates in children 6–16 years of age in a dengue endemic location: Lipa City, Philippines. To achieve this, we will carry out a parallel, two-armed cluster randomised trial evaluating AD efficacy for reducing the incidence of dengue over a 2-year period with 4 consecutive months of vector control during peak dengue transmission each year.

Discussion

For decades, it has been commonly accepted that an integrated approach to mosquito control is required. The World Health Organization (WHO) Global Strategic Framework for Integrated Vector Management recommends a range of interventions, in combination, to increase control impact to reduce transmission. This efficacy trial of the first commercial product using the AD approach will be informative in assessing the general utility of AD in reducing not only adult vector densities but, more importantly, reducing the incidence of dengue. The AD technique may complement source reduction and larviciding campaigns by more efficiently targeting the most productive containers and those beyond human reach. If successful, this mosquito control strategy could prove an invaluable tool in the fight against urban mosquito vectors and a reduction in the burden of associated disease.

Trial registration

ISRCTN44272773. Registered on 31 January 2019.

Electronic supplementary material

The online version of this article (10.1186/s13063-019-3376-6) contains supplementary material, which is available to authorized users.

A new immunoassay of hybrid nanomater conjugated to aptamers for the detection of dengue virus

A new immunosensor using hybrid nanomaterials for the detection of dengue virus was demonstrated in this work. This immunosensor composed of nanoparticles of γ-Fe₂O₃(SAMN) modified with MPA- SAMN@MPA was characterized by FTIR spectroscopy, transmission electron microscopy,quartz crystal microbalance, UV-vis and LSPR technique. The binding of SAMN@MPA with AuNPs conjugated with aptamers(SAMN@MPA@AuNPs@aptamer) provides specific chemical bonds to four dengue serotypes. Colorimetric changes in the modification steps provided rapid visual detection of the virus without the use of equipment. Variations of aptamers concentrations 1.0-10.0 μM where the 3.0 μM aptamer concentration is sufficient to completely cover the surface of the modified AuNPs with an R² value of> 0.99. This new proposed methodology presenting some advantages in relation to traditional detection methods such as time optimization and cost,can be used as a diagnostic method.

Find the right sample: A study on the versatility of saliva and urine samples for the diagnosis of emerging viruses

BACKGROUND

The emergence of different viral infections during the last decades like dengue, West Nile, SARS, chikungunya, MERS-CoV, Ebola, Zika and Yellow Fever raised some questions on quickness and reliability of laboratory diagnostic tests for verification of suspected cases. Since sampling of blood requires medically trained personal and comprises some risks for the patient as well as for the health care personal, the sampling by non-invasive methods (e.g. saliva and/ or urine) might be a very valuable alternative for investigating a diseased patient.

MAIN BODY

To analyse the usefulness of alternative non-invasive samples for the diagnosis of emerging infectious viral diseases, a literature search was performed on PubMed for alternative sampling for these viral infections. In total, 711 papers of potential relevance were found, of which we have included 128 in this review.

CONCLUSIONS

Considering the experience using non-invasive sampling for the diagnostic of emerging viral diseases, it seems important to perform an investigation using alternative samples for routine diagnostics. Moreover, during an outbreak situation, evaluation of appropriate sampling and further processing for laboratory analysis on various diagnostic platforms are very crucial. This will help to achieve optimal diagnostic results for a good and reliable case identification.

Salivary Detection of Dengue Virus NS1 Protein with a Label-Free Immunosensor for Early Dengue Diagnosis

Dengue virus (DENV) is a highly pathogenic, arthropod-borne virus transmitted between people by Aedes mosquitoes. Despite efforts to prevent global spread, the potential for DENV epidemics is increasing world-wide. Annually, 3.6 billion people are at risk of infection. With no licensed vaccine, early diagnosis of dengue infection is critical for clinical management and patient survival. Detection of DENV non-structural protein 1 (NS1) is a clinically accepted biomarker for the early detection of DENV infection. Unfortunately, virtually all of the laboratory and commercial DENV NS1 diagnostic methods require a blood draw for sample analysis, limiting point-of-care diagnostics and decreases patient willingness. Alternatively, NS1 in human saliva has been identified for the potential early diagnosis of DENV infection. The collection of saliva is simple, non-invasive, painless, and inexpensive, even by minimally trained personnel. In this study, we present a label-free chemiresistive immunosensor for the detection of the DENV NS1 protein utilizing a network of single-walled carbon nanotubes functionalized with anti-dengue NS1 monoclonal antibodies. NS1 was successfully detected in adulterated artificial human saliva over the range of clinically relevant concentrations with high sensitivity and selectivity. It has potential application in clinical diagnosis and the ease of collection allows for self-testing, even within the home.

Accuracy of immunoglobulin M and immunoglobulin A of saliva in early diagnosis of dengue: Systematic Review and Meta-analysis

The objective of the study was to conduct a systematic review to synthesize the current evidence on the accuracy of IgM and IgA to early diagnosis the dengue virus. The review protocol was registered at PROSPERO (CRD 42015024808). We searched for studies in the following electronic database from 1990 to January 2018. The search identified 3507 studies. Five studies were included for quantitative analysis. Three studies included evaluations of salivary IgM provided a sensitivity of 86% and specificity of 93%. Two studies included evaluating of IgA salivary showed a combined sensitivity of 69% and a combined specificity of 98%. Despite the results found and the low methodological quality of the studies included in the meta-analysis it is still soon to claim that IgA is better than IgM to diagnosis Dengue.

Rapid antigen tests for dengue virus serotypes and Zika virus in patient serum

The recent Zika virus (ZIKV) outbreak demonstrates that cost-effective clinical diagnostics are urgently needed to detect and distinguish viral infections to improve patient care. Unlike dengue virus (DENV), ZIKV infections during pregnancy correlate with severe birth defects, including microcephaly and neurological disorders. Because ZIKV and DENV are related flaviviruses, their homologous proteins and nucleic acids can cause cross-reactions and false-positive results in molecular, antigenic, and serologic diagnostics. We report the characterization of monoclonal antibody pairs that have been translated into rapid immunochromatography tests to specifically detect the viral nonstructural 1 (NS1) protein antigen and distinguish the four DENV serotypes (DENV1-4) and ZIKV without cross-reaction. To complement visual test analysis and remove user subjectivity in reading test results, we used image processing and data analysis for data capture and test result quantification. Using a 30-μl serum sample, the sensitivity and specificity values of the DENV1-4 tests and the pan-DENV test, which detects all four dengue serotypes, ranged from 0.76 to 1.00. Sensitivity/specificity for the ZIKV rapid test was 0.81/0.86, respectively, using a 150-μl serum input. Serum ZIKV NS1 protein concentrations were about 10-fold lower than corresponding DENV NS1 concentrations in infected patients; moreover, ZIKV NS1 protein was not detected in polymerase chain reaction-positive patient urine samples. Our rapid immunochromatography approach and reagents have immediate application in differential clinical diagnosis of acute ZIKV and DENV cases, and the platform can be applied toward developing rapid antigen diagnostics for emerging viruses.

Emerging souvenirs-clinical presentation of the returning traveller with imported arbovirus infections in Europe

BACKGROUND

Arboviruses are an emerging group of viruses that are causing increasing health concerns globally, including in Europe. Clinical presentation usually consists of a nonspecific febrile illness that may be accompanied by rash, arthralgia and arthritis, with or without neurological or haemorrhagic syndromes. The range of differential diagnoses of other infectious and noninfectious aetiologies is broad, presenting a challenge for physicians. While knowledge of the geographical distribution of pathogens and the current epidemiological situation, incubation periods, exposure risk factors and vaccination history can help guide the diagnostic approach, the nonspecific and variable clinical presentation can delay final diagnosis.

AIMS AND SOURCES

This narrative review aims to summarize the main clinical and laboratory-based findings of the three most common imported arboviruses in Europe. Evidence is extracted from published literature and clinical expertise of European arbovirus experts.

CONTENT

We present three cases that highlight similarities and differences between some of the most common travel-related arboviruses imported to Europe. These include a patient with chikungunya virus infection presenting in Greece, a case of dengue fever in Turkey and a travel-related case of Zika virus infection in Romania.

IMPLICATIONS

Early diagnosis of travel-imported cases is important to reduce the risk of localized outbreaks of tropical arboviruses such as dengue and chikungunya and the risk of local transmission from body fluids or vertical transmission. Given the global relevance of arboviruses and the continuous risk of (re)emerging arbovirus events, clinicians should be aware of the clinical syndromes of arbovirus fevers and the potential pitfalls in diagnosis.

Progress and Challenges towards Point-of-Care Diagnostic Development for Dengue

Dengue detection strategies involve viral RNA, antigen, and/or antibody detection. Each strategy has its advantages and disadvantages. Optimal, user-friendly, rapid diagnostic tests based on immunochromatographic assays are pragmatic point-of-care tests (POCTs) in regions where dengue is endemic where there are limited laboratory capabilities and optimal storage conditions. Increasingly, there is a greater public health significance for a multiplexing assay that differentiates dengue from Zika or pathogens with similar clinical presentations. Although there have been many assay/platform developments toward POCTs, independent validation and implementation remain very limited. This review highlights the current key progress and challenges toward the development of a dengue POCT.