Showing papers on "Dengue fever published in 2014"

Zika virus infection complicated by Guillain-BarrE syndrome – case report, French Polynesia, December 2013

Abstract: Zika fever, considered as an emerging disease of arboviral origin, because of its expanding geographic area, is known as a benign infection usually presenting as an influenza-like illness with cutaneous rash. So far, Zika virus infection has never led to hospitalisation. We describe the first case of Guillain-Barre syndrome (GBS) occurring immediately after a Zika virus infection, during the current Zika and type 1 and 3 dengue fever co-epidemics in French Polynesia.

Current Zika virus epidemiology and recent epidemics.

Abstract: The Zika virus (ZIKV) is a mosquito-borne flavivirus (Aedes), similar to other arboviruses, first identified in Uganda in 1947. Few human cases were reported until 2007, when a Zika outbreak occurred in Yap, Micronesia, even though ZIKV activity had been reported in Africa and in Asia through virological surveillance and entomological studies. French Polynesia has recorded a large outbreak since October 2013. A great number of cases and some with neurological and autoimmune complications have been reported in a context of concurrent circulation of dengue viruses. The clinical presentation is a "dengue-like syndrome". Until the epidemic in French Polynesia, no severe ZIKV disease had been described so far. The diagnosis is confirmed by viral genome detection by genomic amplification (RT- PCR) and viral isolation. These two large outbreaks occurred in a previously unaffected area in less than a decade. They should raise awareness as to the potential for ZIKV to spread especially since this emergent disease is not well known and that some questions remain on potential reservoirs and transmission modes as well as on clinical presentations and complications. ZIKV has the potential to spread to new areas where the Aedes mosquito vector is present and could be a risk for Southern Europe. Strategies for the prevention and control of ZIKV disease should include the use of insect repellent and mosquito vector eradication.

Zika virus, French Polynesia, South Pacific, 2013.

Abstract: To the Editor: We wish to clarify an inaccuracy in a letter in Emerging Infectious Diseases by Cao-Lormeau et al (1) The authors state “In 2007, the first ZIKV outbreak reported outside Africa and Asia was retrospectively documented from biological samples from patients on Yap Island, Federated States of Micronesia, North Pacific, who had received an incorrect diagnosis of dengue virus (DENV)” Although the first outbreak of Zika virus (ZIKV) infection reported outside Africa or Asia was in Yap, it was not retrospectively identified from serum samples incorrectly diagnosed as positive for dengue virus The outbreak was first identified by the Yap State Department of Health Services, and an investigation to determine the etiologic agent was initiated Although dengue was initially part of the differential diagnosis, and a few patients had evidence of IgM against dengue virus by a rapid diagnostic test, clinicians in Yap believed that the clinical syndrome was not consistent with dengue Thus, assistance was requested from the US Centers for Disease Control and Prevention and the World Health Organization to strengthen the epidemiologic investigation and provide confirmatory laboratory testing Serum samples collected during the active investigation were sent to the Arboviral Diseases Diagnostic Laboratory at the Centers for Disease Control and Prevention where testing determined that the cause of the infections was ZIKV (2) This discovery of ZIKV as the etiologic agent was not achieved through retrospective testing of serum from patients incorrectly diagnosed as having dengue, but rather the result of an active, coordinated investigation by the Yap State Department of Health Services with instrumental assistance from international partners

Concurrent outbreaks of dengue, chikungunya and Zika virus infections - an unprecedented epidemic wave of mosquito-borne viruses in the Pacific 2012-2014.

Abstract: Since January 2012, the Pacific Region has experienced 28 new documented outbreaks and circulation of dengue, chikungunya and Zika virus. These mosquito-borne disease epidemics seem to become more frequent and diverse, and it is likely that this is only the early stages of a wave that will continue for several years. Improved surveillance and response measures are needed to mitigate the already heavy burden on island health systems and limit further spread to other parts of the world.

Flavivirus NS1 structures reveal surfaces for associations with membranes and the immune system.

Abstract: Flaviviruses, the human pathogens responsible for dengue fever, West Nile fever, tick-borne encephalitis, and yellow fever, are endemic in tropical and temperate parts of the world. The flavivirus nonstructural protein 1 (NS1) functions in genome replication as an intracellular dimer and in immune system evasion as a secreted hexamer. We report crystal structures for full-length, glycosylated NS1 from West Nile and dengue viruses. The NS1 hexamer in crystal structures is similar to a solution hexamer visualized by single-particle electron microscopy. Recombinant NS1 binds to lipid bilayers and remodels large liposomes into lipoprotein nanoparticles. The NS1 structures reveal distinct domains for membrane association of the dimer and interactions with the immune system and are a basis for elucidating the molecular mechanism of NS1 function.

Global temperature constraints on Aedes aegypti and Ae. albopictus persistence and competence for dengue virus transmission

Abstract: Dengue is a disease that has undergone significant expansion over the past hundred years. Understanding what factors limit the distribution of transmission can be used to predict current and future limits to further dengue expansion. While not the only factor, temperature plays an important role in defining these limits. Previous attempts to analyse the effect of temperature on the geographic distribution of dengue have not considered its dynamic intra-annual and diurnal change and its cumulative effects on mosquito and virus populations. Here we expand an existing modelling framework with new temperature-based relationships to model an index proportional to the basic reproductive number of the dengue virus. This model framework is combined with high spatial and temporal resolution global temperature data to model the effects of temperature on Aedes aegypti and Ae. albopictus persistence and competence for dengue virus transmission. Our model predicted areas where temperature is not expected to permit transmission and/or Aedes persistence throughout the year. By reanalysing existing experimental data our analysis indicates that Ae. albopictus, often considered a minor vector of dengue, has comparable rates of virus dissemination to its primary vector, Ae. aegypti, and when the longer lifespan of Ae. albopictus is considered its competence for dengue virus transmission far exceeds that of Ae. aegypti. These results can be used to analyse the effects of temperature and other contributing factors on the expansion of dengue or its Aedes vectors. Our finding that Ae. albopictus has a greater capacity for dengue transmission than Ae. aegypti is contrary to current explanations for the comparative rarity of dengue transmission in established Ae. albopictus populations. This suggests that the limited capacity of Ae. albopictus to transmit DENV is more dependent on its ecology than vector competence. The recommendations, which we explicitly outlined here, point to clear targets for entomological investigation.

Limited Dengue Virus Replication in Field-Collected Aedes aegypti Mosquitoes Infected with Wolbachia

Abstract: Introduction Dengue is one of the most widespread mosquito-borne diseases in the world. The causative agent, dengue virus (DENV), is primarily transmitted by the mosquito Aedes aegypti, a species that has proved difficult to control using conventional methods. The discovery that A. aegypti transinfected with the wMel strain of Wolbachia showed limited DENV replication led to trial field releases of these mosquitoes in Cairns, Australia as a biocontrol strategy for the virus. Methodology/Principal Findings Field collected wMel mosquitoes that were challenged with three DENV serotypes displayed limited rates of body infection, viral replication and dissemination to the head compared to uninfected controls. Rates of dengue infection, replication and dissemination in field wMel mosquitoes were similar to those observed in the original transinfected wMel line that had been maintained in the laboratory. We found that wMel was distributed in similar body tissues in field mosquitoes as in laboratory ones, but, at seven days following blood-feeding, wMel densities increased to a greater extent in field mosquitoes. Conclusions/Significance Our results indicate that virus-blocking is likely to persist in Wolbachia-infected mosquitoes after their release and establishment in wild populations, suggesting that Wolbachia biocontrol may be a successful strategy for reducing dengue transmission in the field.

Limited dengue virus replication in field-collected Aedes aegypti mosquitoes infected with Wolbachia

Abstract: Introduction Dengue is one of the most widespread mosquito-borne diseases in the world The causative agent, dengue virus (DENV), is primarily transmitted by the mosquito Aedes aegypti, a species that has proved difficult to control using conventional methods The discovery that A aegypti transinfected with the wMel strain of Wolbachia showed limited DENV replication led to trial field releases of these mosquitoes in Cairns, Australia as a biocontrol strategy for the virus Methodology/Principal Findings Field collected wMel mosquitoes that were challenged with three DENV serotypes displayed limited rates of body infection, viral replication and dissemination to the head compared to uninfected controls Rates of dengue infection, replication and dissemination in field wMel mosquitoes were similar to those observed in the original transinfected wMel line that had been maintained in the laboratory We found that wMel was distributed in similar body tissues in field mosquitoes as in laboratory ones, but, at seven days following blood-feeding, wMel densities increased to a greater extent in field mosquitoes Conclusions/Significance Our results indicate that virus-blocking is likely to persist in Wolbachia-infected mosquitoes after their release and establishment in wild populations, suggesting that Wolbachia biocontrol may be a successful strategy for reducing dengue transmission in the field

Assessing the Relationship between Vector Indices and Dengue Transmission: A Systematic Review of the Evidence

Abstract: Background Despite doubts about methods used and the association between vector density and dengue transmission, routine sampling of mosquito vector populations is common in dengue-endemic countries worldwide This study examined the evidence from published studies for the existence of any quantitative relationship between vector indices and dengue cases Methodology/Principal Findings From a total of 1205 papers identified in database searches following Cochrane and PRISMA Group guidelines, 18 were included for review Eligibility criteria included 3-month study duration and dengue case confirmation by WHO case definition and/or serology A range of designs were seen, particularly in spatial sampling and analyses, and all but 3 were classed as weak study designs Eleven of eighteen studies generated Stegomyia indices from combined larval and pupal data Adult vector data were reported in only three studies Of thirteen studies that investigated associations between vector indices and dengue cases, 4 reported positive correlations, 4 found no correlation and 5 reported ambiguous or inconclusive associations Six out of 7 studies that measured Breteau Indices reported dengue transmission at levels below the currently accepted threshold of 5 Conclusions/Significance There was little evidence of quantifiable associations between vector indices and dengue transmission that could reliably be used for outbreak prediction This review highlighted the need for standardized sampling protocols that adequately consider dengue spatial heterogeneity Recommendations for more appropriately designed studies include: standardized study design to elucidate the relationship between vector abundance and dengue transmission; adult mosquito sampling should be routine; single values of Breteau or other indices are not reliable universal dengue transmission thresholds; better knowledge of vector ecology is required

Dengue Antibody-Dependent Enhancement: Knowns and Unknowns

Abstract: Dengue provides the most abundant example in human medicine and the greatest human illness burden caused by the phenomenon of intrinsic antibody-dependent infection enhancement (iADE). In this immunopathological phenomenon infection of monocytes or macrophages using infectious immune complexes suppresses innate antiviral systems, permitting logarithmic intracellular growth of dengue virus. The four dengue viruses evolved from a common ancestor yet retain similar ecology and pathogenicity, but although infection with one virus provides short-term cross-protection against infection with a different type, millions of secondary dengue infections occur worldwide each year. When individuals are infected in the virtual absence of cross-protective dengue antibodies, the dengue vascular permeability syndrome (DVPS) may ensue. This occurs in around 2 to 4% of second heterotypic dengue infections. A complete understanding of the biologic mechanism of iADE, dengue biology, and the mechanism of host responses to dengue infection should lead to a comprehensive and complete understanding of the pathogenesis of DVPS. A crucial emphasis must be placed on understanding ADE. Clinical and epidemiological observations of DVPS define the research questions and provide research parameters. This article will review knowledge related to dengue ADE and point to areas where there has been little research progress. These observations relate to the two stages of dengue illnesses: afferent phenomena are those that promote the success of the microorganism to infect and survive; efferent phenomena are those mounted by the host to inhibit infection and replication and to eliminate the infectious agent and infected tissues. Data will be discussed as "knowns" and "unknowns."

Chromobacterium Csp_P Reduces Malaria and Dengue Infection in Vector Mosquitoes and Has Entomopathogenic and In Vitro Anti-pathogen Activities

Abstract: Plasmodium and dengue virus, the causative agents of the two most devastating vector-borne diseases, malaria and dengue, are transmitted by the two most important mosquito vectors, Anopheles gambiae and Aedes aegypti, respectively. Insect-bacteria associations have been shown to influence vector competence for human pathogens through multi-faceted actions that include the elicitation of the insect immune system, pathogen sequestration by microbes, and bacteria-produced anti-pathogenic factors. These influences make the mosquito microbiota highly interesting from a disease control perspective. Here we present a bacterium of the genus Chromobacterium (Csp_P), which was isolated from the midgut of field-caught Aedes aegypti. Csp_P can effectively colonize the mosquito midgut when introduced through an artificial nectar meal, and it also inhibits the growth of other members of the midgut microbiota. Csp_P colonization of the midgut tissue activates mosquito immune responses, and Csp_P exposure dramatically reduces the survival of both the larval and adult stages. Ingestion of Csp_P by the mosquito significantly reduces its susceptibility to Plasmodium falciparum and dengue virus infection, thereby compromising the mosquito's vector competence. This bacterium also exerts in vitro anti-Plasmodium and anti-dengue activities, which appear to be mediated through Csp_P -produced stable bioactive factors with transmission-blocking and therapeutic potential. The anti-pathogen and entomopathogenic properties of Csp_P render it a potential candidate for the development of malaria and dengue control strategies.

First case of Zika virus infection in a returning Canadian traveler.

Abstract: A woman who recently traveled to Thailand came to a local emergency department with a fever and papular rash. She was tested for measles, malaria, and dengue. Positive finding for IgM antibody against dengue and a failure to seroconvert for IgG against dengue for multiple blood samples suggested an alternate flavivirus etiology. Amplification of a conserved region of the non-structural protein 5 gene of the genus Flavivirus yielded a polymerase chain reaction product with a matching sequence of 99% identity with Zika virus. A urine sample and a nasopharygeal swab specimen obtained for the measles investigation were also positive for this virus by reverse transcription polymerase chain reaction. Subsequently, the urine sample yielded a Zika virus isolate in cell culture. This case report describes a number of novel clinical and laboratory findings, the first documentation of this virus in Canada, and the second documentation from this region in Thailand.

Emergency department management of mosquito-borne illness: malaria, dengue, and West Nile virus.

Abstract: Up to 700 million people are infected and more than a million die each year from mosquito-borne illness. While the vast majority of cases occur in endemic tropical and subtropical regions, international travel and migration patterns have increased their prevalence in North America. This review discusses the diagnosis and treatment of the 3 most common mosquito-borne illnesses seen in the United States: Plasmodium falciparum malaria, dengue, and West Nile virus. With no pathognomonic findings, it is critical that emergency clinicians in nonendemic areas maintain a high index of suspicion, conduct a thorough history/travel history, and interpret indirect findings to initiate prompt and appropriate treatment. This review gathers the best evidence from international public health resources, surveillance studies, guidelines, and academic research to give emergency clinicians tools to combat these potentially lethal infections.

First case of laboratory-confirmed Zika virus infection imported into Europe, November 2013.

Abstract: In November 2013, an acute Zika virus (ZIKV) infection was diagnosed in a German traveller returning from Thailand. The patient reported a clinical picture resembling dengue fever. Serological investigations revealed anti-ZIKV-IgM and -IgG, as well as ZIKV-specific neutralising antibodies in the patient's blood. In Europe, viraemic travellers may become a source of local transmission of ZIKV, because Aedes albopictus (Skuse) and Ae. aegypti (Linnaeus) are invasive mosquitoes and competent vectors for ZIKV. .

Dengue and dengue vectors in the WHO European region: past, present, and scenarios for the future

Abstract: After 55 years of absence, dengue has re-emerged in the WHO European region both as locally transmitted sporadic cases and as an outbreak in Madeira, driven by the introduction of people infected with the virus and the invasion of the vector mosquito species Aedes aegypti and Aedes albopictus. Models predict a further spread of A albopictus, particularly under climate change conditions. Dengue transmission models suggest a low risk in Europe, but these models too rarely include transmission by A albopictus (the main established vector). Further information gaps exist with regard to the Caucasus and central Asian countries of the WHO European region. Many European countries have implemented surveillance and control measures for invasive mosquitoes, but only a few include surveillance for dengue. As long as no dengue-specific prophylaxis or therapeutics are available, integrated vector management is the most sustainable control option. The rapid elimination of newly introduced A aegypti populations should be targeted in the European region, particularly in southern Europe and the Caucasus, where the species was present for decades until the 1950s.

RNA structures that resist degradation by Xrn1 produce a pathogenic Dengue virus RNA

Abstract: More than 40% of people around the globe are at risk of being bitten by mosquitoes infected with the virus that causes Dengue fever. Every year, more than 100 million of these individuals are infected. Many develop severe headaches, pain, and fever, but some develop a life-threatening condition where tiny blood vessels in the body begin to leak. If not treated quickly, this more severe manifestation of the illness can lead to death. There are currently no specific therapies or vaccines against Dengue or many other closely related viruses such as West Nile and Japanese Encephalitis. These viruses use instructions encoded in a single strand of RNA to take over an infected cell and to reproduce. The viruses also exploit an enzyme that cells use to destroy RNA to instead produce short stretches of RNA called sfRNAs that, among other things, may help the virus to avoid the immune system of its host. Understanding exactly how Dengue and other viruses thwart this enzyme—which is called Xrn1—may help scientists develop treatments or vaccines for these diseases. Chapman et al. have now shown that Dengue virus RNA contains a number of RNA elements that prevent it being completely degraded by the Xrn1 enzyme. In particular, a junction formed by three RNA helixes is critical for stopping the enzyme in its tracks, leaving the disease-associated sfRNA behind. A single mutation in the Dengue RNA disrupts the structure of the three-helix junction and allows the enzyme to completely destroy the RNA. A similar mutation was also made in the West Nile virus RNA and when human cells were infected with the mutated West Nile virus, the short sfRNAs were not produced. Treatments or vaccines targeting this structure may therefore help reduce illness associated with Dengue and related viruses.

Aedes hensilli as a potential vector of Chikungunya and Zika viruses.

Abstract: An epidemic of Zika virus (ZIKV) illness that occurred in July 2007 on Yap Island in the Federated States of Micronesia prompted entomological studies to identify both the primary vector(s) involved in transmission and the ecological parameters contributing to the outbreak. Larval and pupal surveys were performed to identify the major containers serving as oviposition habitat for the likely vector(s). Adult mosquitoes were also collected by backpack aspiration, light trap, and gravid traps at select sites around the capital city. The predominant species found on the island was Aedes (Stegomyia) hensilli. No virus isolates were obtained from the adult field material collected, nor did any of the immature mosquitoes that were allowed to emerge to adulthood contain viable virus or nucleic acid. Therefore, laboratory studies of the probable vector, Ae. hensilli, were undertaken to determine the likelihood of this species serving as a vector for Zika virus and other arboviruses. Infection rates of up to 86%, 62%, and 20% and dissemination rates of 23%, 80%, and 17% for Zika, chikungunya, and dengue-2 viruses respectively, were found supporting the possibility that this species served as a vector during the Zika outbreak and that it could play a role in transmitting other medically important arboviruses.

The Pathology of Severe Dengue in Multiple Organs of Human Fatal Cases: Histopathology, Ultrastructure and Virus Replication

Abstract: Dengue is a public health problem, with several gaps in understanding its pathogenesis. Studies based on human fatal cases are extremely important and may clarify some of these gaps. In this work, we analyzed lesions in different organs of four dengue fatal cases, occurred in Brazil. Tissues were prepared for visualization in optical and electron microscopy, with damages quantification. As expected, we observed in all studied organ lesions characteristic of severe dengue, such as hemorrhage and edema, although other injuries were also detected. Cases presented necrotic areas in the liver and diffuse macro and microsteatosis, which were more accentuated in case 1, who also had obesity. The lung was the most affected organ, with hyaline membrane formation associated with mononuclear infiltrates in patients with pre-existing diseases such as diabetes and obesity (cases 1 and 2, respectively). These cases had also extensive acute tubular necrosis in the kidney. Infection induced destruction of cardiac fibers in most cases, with absence of nucleus and loss of striations, suggesting myocarditis. Spleens revealed significant destruction of the germinal centers and atrophy of lymphoid follicles, which may be associated to decrease of T cell number. Circulatory disturbs were reinforced by the presence of megakaryocytes in alveolar spaces, thrombus formation in glomerular capillaries and loss of endothelium in several tissues. Besides histopathological and ultrastructural observations, virus replication were investigated by detection of dengue antigens, especially the non-structural 3 protein (NS3), and confirmed by the presence of virus RNA negative strand (in situ hybridization), with second staining for identification of some cells. Results showed that dengue had broader tropism comparing to what was described before in literature, replicating in hepatocytes, type II pneumocytes and cardiac fibers, as well as in resident and circulating monocytes/macrophages and endothelial cells.

Efficacy and safety of celgosivir in patients with dengue fever (CELADEN): a phase 1b, randomised, double-blind, placebo-controlled, proof-of-concept trial.

Abstract: Summary Background Dengue infection is the most common mosquito-borne viral disease worldwide, but no suitable antiviral drugs are available. We tested the α-glucosidase inhibitor celgosivir as a treatment for acute dengue fever. Methods To establish eligibility for inclusion in a phase 1b, randomised, double-blind, placebo-controlled, proof-of-concept trial, individuals aged 21–65 years who had had a fever (≥38°C) for less than 48 h, met at least two criteria indicating probable dengue infection, and had a positive result on a dengue point-of-care test kit or PCR assay were referred for screening at a centre in Singapore between July 30, 2012, and March 4, 2013. Using a web-based system, we randomly assigned patients who met full inclusion criteria after screening (1:1; random permuted block length four) to celgosivir (initial 400 mg loading dose within 6 h of randomisation, followed by 200 mg every 12 h for a total of nine doses) or matched placebo. Patients and the entire study team were masked to group assignment. The primary endpoints were mean virological log reduction (VLR) from baseline for days 2, 3, and 4, and area under the fever curve (AUC) for a temperature above 37°C from 0 h to 96 h. Efficacy analyses were by intention to treat. This study is registered with ClinicalTrials.gov, number NCT01619969. Findings We screened 69 patients and randomly assigned 50 (24 to celgosivir, 26 to placebo). Mean VLR was greater in the celgosivir group (–1·86, SD 1·07) than in the placebo group (–1·64, 0·75), but the difference was non-significant (–0·22, 90% CI −0·65 to 0·22; one-sided p=0·203). The mean AUC was also higher in the celgosivir group (54·92, SD 31·04) than in the placebo group (40·72, 18·69), but again the difference was non-significant (14·20, 90% CI 2·16–26·25; one-sided p=0·973). We noted similar incidences of adverse events between groups. Interpretation Although generally safe and well tolerated, celgosivir does not seem to reduce viral load or fever burden in patients with dengue. Funding STOP Dengue Translational Clinical Research.

A Shorter Time Interval Between First and Second Dengue Infections Is Associated With Protection From Clinical Illness in a School-based Cohort in Thailand

Abstract: Background. Despite the strong association between secondary dengue virus (DENV) infections and dengue hemorrhagic fever (DHF), the majority of secondary infections are subclinical or mild. The determinants of clinical severity remain unclear, though studies indicate a titer-dependent and time-dependent role of cross-protective anti-DENV antibodies. Methods. Data from 2 sequential prospective cohort studies were analyzed for subclinical and symptomatic DENV infections in schoolchildren in Kamphaeng Phet, Thailand (1998–2002 and 2004–2007). Children experiencing ≥1 DENV infection were selected as the population for analysis (contributing 2169 person-years of follow-up). Results. In total, 1696 children had ≥1 DENV infection detected during their enrollment; 268 experienced 2 or more infections. A shorter time interval between infections was associated with subclinical infection in children seronegative for DENV at enrollment, for whom a second-detected DENV infection is more likely to reflect a true second infection (average of 2.6 years between infections for DHF, 1.9 for DF, and 1.6 for subclinical infections). Conclusions. These findings support a pathogenesis model where cross-reactive antibodies wane from higher-titer, protective levels to lower-titer, detrimental levels. This is one of the first studies of human subjects to suggest a window of cross-protection following DENV infection since Sabin's challenge studies in the 1940s.

Ultrastructural Characterization and Three-Dimensional Architecture of Replication Sites in Dengue Virus-Infected Mosquito Cells

Abstract: During dengue virus infection of host cells, intracellular membranes are rearranged into distinct subcellular structures such as double-membrane vesicles, convoluted membranes, and tubular structures. Recent electron tomographic studies have provided a detailed three-dimensional architecture of the double-membrane vesicles, representing the sites of dengue virus replication, but temporal and spatial evidence linking membrane morphogenesis with viral RNA synthesis is lacking. Integrating techniques in electron tomography and molecular virology, we defined an early period in virus-infected mosquito cells during which the formation of a virus-modified membrane structure, the double-membrane vesicle, is proportional to the rate of viral RNA synthesis. Convoluted membranes were absent in dengue virus-infected C6/36 cells. Electron tomographic reconstructions elucidated a high-resolution view of the replication complexes inside vesicles and allowed us to identify distinct pathways of particle formation. Hence, our findings extend the structural details of dengue virus replication within mosquito cells and highlight their differences from mammalian cells. IMPORTANCE Dengue virus induces several distinct intracellular membrane structures within the endoplasmic reticulum of mammalian cells. These structures, including double-membrane vesicles and convoluted membranes, are linked, respectively, with viral replication and viral protein processing. However, dengue virus cycles between two disparate animal groups with differing physiologies: mammals and mosquitoes. Using techniques in electron microscopy, we examined the differences between intracellular structures induced by dengue virus in mosquito cells. Additionally, we utilized techniques in molecular virology to temporally link events in virus replication to the formation of these dengue virus-induced membrane structures.

Evaluation of commercially available diagnostic tests for the detection of dengue virus NS1 antigen and anti-dengue virus IgM antibody.

Abstract: Commercially available diagnostic test kits for detection of dengue virus (DENV) non-structural protein 1 (NS1) and anti-DENV IgM were evaluated for their sensitivity and specificity and other performance characteristics by a diagnostic laboratory network developed by World Health Organization (WHO), the UNICEF/UNDP/World Bank/WHO Special Programme for Research and Training in Tropical Diseases (TDR) and the Pediatric Dengue Vaccine Initiative (PDVI). Each network laboratory contributed characterized serum specimens for the panels used in the evaluation. Microplate enzyme-linked immunosorbent assay (ELISA) and rapid diagnostic test (RDT formats) were represented by the kits. Each ELISA was evaluated by 2 laboratories and RDTs were evaluated by at least 3 laboratories. The reference tests for IgM anti-DENV were laboratory developed assays produced by the Armed Forces Research Institute for Medical Science (AFRIMS) and the Centers for Disease Control and Prevention (CDC), and the NS1 reference test was reverse transcriptase polymerase chain reaction (RT-PCR). Results were analyzed to determine sensitivity, specificity, inter-laboratory and inter-reader agreement, lot-to-lot variation and ease-of-use. NS1 ELISA sensitivity was 60–75% and specificity 71–80%; NS1 RDT sensitivity was 38–71% and specificity 76–80%; the IgM anti-DENV RDTs sensitivity was 30–96%, with a specificity of 86–92%, and IgM anti-DENV ELISA sensitivity was 96–98% and specificity 78–91%. NS1 tests were generally more sensitive in specimens from the acute phase of dengue and in primary DENV infection, whereas IgM anti-DENV tests were less sensitive in secondary DENV infections. The reproducibility of the NS1 RDTs ranged from 92-99% and the IgM anti-DENV RDTs from 88–94%.

Evaluation of dengue NS1 antigen rapid tests and ELISA kits using clinical samples.

Abstract: Background Early diagnosis of dengue virus (DENV) infection can improve clinical outcomes by ensuring close follow-up, initiating appropriate supportive therapies and raising awareness to the potential of hemorrhage or shock. Non-structural glycoprotein-1 (NS1) has proven to be a useful biomarker for early diagnosis of dengue. A number of rapid diagnostic tests (RDTs) and enzyme-linked immunosorbent assays (ELISAs) targeting NS1 antigen (Ag) are now commercially available. Here we evaluated these tests using a well-characterized panel of clinical samples to determine their effectiveness for early diagnosis. Methodology/Principal Findings Retrospective samples from South America were used to evaluate the following tests: (i) “Dengue NS1 Ag STRIP” and (ii) “Platelia Dengue NS1 Ag ELISA” (Bio-Rad, France), (iii) “Dengue NS1 Detect Rapid Test (1st Generation)” and (iv) “DENV Detect NS1 ELISA” (InBios International, United States), (v) “Panbio Dengue Early Rapid (1st generation)” (vi) “Panbio Dengue Early ELISA (2nd generation)” and (vii) “SD Bioline Dengue NS1 Ag Rapid Test” (Alere, United States). Overall, the sensitivity of the RDTs ranged from 71.9%–79.1% while the sensitivity of the ELISAs varied between 85.6–95.9%, using virus isolation as the reference method. Most tests had lower sensitivity for DENV-4 relative to the other three serotypes, were less sensitive in detecting secondary infections, and appeared to be most sensitive on Day 3–4 post symptom onset. The specificity of all evaluated tests ranged from 95%–100%. Conclusions ELISAs had greater overall sensitivity than RDTs. In conjunction with other parameters, the performance data can help determine which dengue diagnostics should be used during the first few days of illness, when the patients are most likely to present to a clinic seeking care.

Incubation periods of mosquito-borne viral infections: a systematic review.

Abstract: Mosquito-borne viruses are a major public health threat, but their incubation periods are typically uncited, non-specific, and not based on data. We systematically review the published literature on six mosquito-borne viruses selected for their public health importance: chikungunya, dengue, Japanese encephalitis, Rift Valley fever, West Nile, and yellow fever viruses. For each, we identify the literature's consensus on the incubation period, evaluate the evidence for this consensus, and provide detailed estimates of the incubation period and distribution based on published experimental and observational data. We abstract original data as doubly interval-censored observations. Assuming a log-normal distribution, we estimate the median incubation period, dispersion, 25th and 75th percentiles by maximum likelihood. We include bootstrapped 95% confidence intervals for each estimate. For West Nile and yellow fever viruses, we also estimate the 5th and 95th percentiles of their incubation periods.