Dogma in classifying dengue disease

Utility of the WHO dengue guidelines in pediatric immunological studies

Dengue is a significant health problem due to the high burden of critical infections during outbreaks. In 1997, the World Health Organization (WHO) classified dengue as dengue fever (DF), dengue hemorrhagic fever (DHF), and dengue shock syndrome (DSS). It was revised in 2009 (updated in 2015), and the new guidelines recommended classifying patients as dengue without warning signs (DNS), dengue with warning signs (DWS), and severe dengue (SD). Although the utility of the revised 2009 classification for clinical studies is accepted, for immunological studies it needs to be clarified. We determined the usefulness of the 2009 classification for pediatric studies that analyze the circulating interleukin (IL)-6 and IL-8, two inflammatory cytokines. Plasma levels of IL-6 and IL-8 were evaluated in the acute and convalescent phases by flow cytometry in children with dengue classified using the 1997 and 2009 WHO guidelines. The plasma levels of IL-6 and IL-8 were elevated during the acute and decreased during convalescence, and both cytokines served as a good marker of acute dengue illness compared to convalescence. There were no differences in the plasma level of the evaluated cytokines among children with different clinical severity with any classification, except for the IL-8, which was higher in DWS than DNS. Based on the levels of IL-8, the 2009 classification identified DWS plus SD (hospital-treated children) compared to the DNS group [area under the curve (AUC): 0.7, p = 0.028]. These results support the utility of the revised 2009 (updated in 2015) classification in studies of immune markers in pediatric dengue.

Severe disease during both primary and secondary dengue virus infections in pediatric populations

Dengue is a global epidemic causing over 100 million cases annually. The clinical symptoms range from mild fever to severe hemorrhage and shock, including some fatalities. The current paradigm is that these severe dengue cases occur mostly during secondary infections due to antibody-dependent enhancement after infection with a different dengue virus serotype. India has the highest dengue burden worldwide, but little is known about disease severity and its association with primary and secondary dengue infections. To address this issue, we examined 619 children with febrile dengue-confirmed infection from three hospitals in different regions of India. We classified primary and secondary infections based on IgM:IgG ratios using a dengue-specific enzyme-linked immunosorbent assay according to the World Health Organization guidelines. We found that primary dengue infections accounted for more than half of total clinical cases (344 of 619), severe dengue cases (112 of 202) and fatalities (5 of 7). Consistent with the classification based on binding antibody data, dengue neutralizing antibody titers were also significantly lower in primary infections compared to secondary infections (P ≤ 0.0001). Our findings question the currently widely held belief that severe dengue is associated predominantly with secondary infections and emphasizes the importance of developing vaccines or treatments to protect dengue-naive populations.

Majority of pediatric dengue virus infections in Kenya do not meet 2009 WHO criteria for dengue diagnosis

From 1975-2009, the WHO guidelines classified symptomatic dengue virus infections as dengue fever, dengue hemorrhagic fever, and dengue shock syndrome. In 2009 the case definition was changed to a clinical classification after concern the original criteria was challenging to apply in resource-limited settings and not inclusive of a substantial proportion of severe dengue cases. Our goal was to examine how well the current WHO definition identified new dengue cases at our febrile surveillance sites in Kenya. Between 2014 and 2019 as part of a child cohort study of febrile illness in our four clinical study sites (Ukunda, Kisumu, Msambweni, Chulaimbo) we identified 369 dengue PCR positive symptomatic cases and characterized whether they met the 2009 revised WHO diagnostic criteria for dengue with and without warning signs and severe dengue. We found 62% of our PCR-confirmed dengue cases did not meet criteria per the guidelines. Our findings also correlate with our experience that dengue disease in children in Kenya is less severe as reported in other parts of the world. Although the 2009 clinical classification has recently been criticized for being overly inclusive and non-specific, our findings suggest the 2009 WHO dengue case definition may miss more than 50% of symptomatic infections in Kenya and may require further modification to include the African experience.

Determining Risk Factors for Dengue Fever Severity in Jeddah City, a Case-Control Study (2017)

Dengue fever is a major public health problem in Saudi Arabia. Unfortunately, preventive strategies are still deficient. It can progress to severe and lethal forms, and available knowledge does not allow early prediction of which cases of dengue fever (DF) will progress to dengue hemorrhagic fever (DHF). The aim of this study was to evaluate the host and viral factors that could play a role in the progression of severe dengue cases in the frame of the revised 2009 WHO classification. Data were compiled from the Jeddah Dengue Fever Operation Room (DFOR) in the Maden Al-Fahd primary healthcare center in Jeddah. An unmatched case-control study was conducted on 123 severe cases, and 245 controls (non-severe cases) diagnosed during 2014-2016. Risk factors for severe dengue fever were secondary infection (p = 0.02), and co-morbidities, particularly diabetes and hypertension (p < 0.001). Age, gender, nationality, socioeconomic status, viral serotype, and access to health care were not significantly associated with severe disease. The main risk factors for severe dengue fever were secondary infection, and co-morbidities (hypertension and diabetes). We recommend disseminating these data to stakeholders to improve dengue control interventions in periods with anticipated high incidence.

Severe dengue categories as research endpoints-Results from a prospective observational study in hospitalised dengue patients

Severe dengue was perceived as one clinical disease entity until the WHO 2009 classification stratified it into severe vascular leakage, severe bleeding, and severe organ dysfunction. The objectives of this study were to investigate the potential use of severe dengue categories as endpoints for intervention research. 271 patients with severe dengue among 1734 confirmed dengue patients were followed prospectively in this hospital-based observational study in Latin America and Asia. We compared the distribution of severe dengue categories according to gender and age (below/above 15y), and determined the relative frequency and the overlap of severe dengue categories in the same patients. In a next step, we extended the analysis to candidate moderate severity categories, based on recently suggested definitions which were adapted for our purposes. Severe vascular leakage occurred in 244 (90%), severe bleeding in 39 (14%), and severe organ dysfunction in 28 (10%) of 271 severe dengue patients. A higher frequency of severe leakage was seen in children or adolescents (<15y) compared to adults. More than 80% of the severe leakage cases, and 30-50% of the cases with severe bleeding or severe organ dysfunction, were defined as severe on the basis of that feature alone. In 136 out of 213 patients with severe leakage alone, neither moderate bleeding manifestation nor hepatic involvement was recorded. On the other hand, moderate leakage manifestations were detected in 4 out of 12 cases that were classified as severe based on bleeding alone. A major proportion of severe dengue patients exhibited clinical manifestations of severe vascular leakage only, which may constitute a useful endpoint for intervention research or pathophysiology studies. Severe bleeding and severe organ manifestation were recorded less frequently and exhibited a higher degree of overlap with severe leakage. Severe bleeding without leakage may be associated with individual predisposition or the presence of comorbidities. More detailed assessments are needed to explore this hypothesis. Candidate moderate disease endpoints were investigated and need to be further validated.

Yellow fever (YF) vaccination does not increase dengue severity: A retrospective study based on 11,448 dengue notifications in a YF and dengue endemic region

BACKGROUND

We study the association between prior yellow fever immunization and clinical outcomes of dengue infections in individuals of varying sexes and ages. Serological interactions between dengue virus and other flaviviruses could drive antibody dependent enhancement, which is associated with disease severity in dengue infections. This effect may influence disease severity in individuals subsequently affected by related flaviviruses, such as dengue. We compare the severity of dengue episodes between patients vaccinated and non-vaccinated against yellow fever.

METHODS

We evaluated the severity of 11,448 lab-confirmed dengue cases reported in São José do Rio Preto, Brazil, in 7370 YF vaccinated patients compared to 4043 unvaccinated patients. We regressed dengue severity against YF vaccine status and a number of demographic, clinical, and laboratory variables as controls. We also evaluated the association between YF vaccination status and the clinical and laboratory symptoms of dengue patients.

RESULTS

We did not find any evidence of increased risk for severe dengue in patients vaccinated against YF (odds ratio = 1.00; 95% confidence interval = 0.87-1.14). Most of the variables analyzed did not have a statistically significant association with YF vaccination status.

CONCLUSIONS

We found no evidence that YF vaccination in dengue-endemic areas increases the risk of severe dengue fever.

Dengue

Mortality from severe dengue is low, but the economic and resource burden on health services remains substantial in endemic settings. Unfortunately, progress towards development of effective therapeutics has been slow, despite notable advances in the understanding of disease pathogenesis and considerable investment in antiviral drug discovery. For decades antibody-dependent enhancement has been the prevalent model to explain dengue pathogenesis, but it was only recently demonstrated in vivo and in clinical studies. At present, the current mainstay of management for most symptomatic dengue patients remains careful observation and prompt but judicious use of intravenous hydration therapy for those with substantial vascular leakage. Various new promising technologies for diagnosis of dengue are currently in the pipeline. New sample-in, answer-out nucleic acid amplification technologies for point-of-care use are being developed to improve performance over current technologies, with the potential to test for multiple pathogens using a single specimen. The search for biomarkers that reliably predict development of severe dengue among symptomatic individuals is also a major focus of current research efforts. The first dengue vaccine was licensed in 2015 but its performance depends on serostatus. There is an urgent need to identify correlates of both vaccine protection and disease enhancement. A crucial assessment of vector control tools should guide a research agenda for determining the most effective interventions, and how to best combine state-of-the-art vector control with vaccination.

Development of standard clinical endpoints for use in dengue interventional trials: introduction and methodology

Background

As increasing numbers of dengue vaccines and therapeutics are in clinical development, standardized consensus clinical endpoint definitions are urgently needed to assess the efficacy of different interventions with respect to disease severity. We aimed to convene dengue experts representing various sectors and dengue endemic areas to review the literature and propose clinical endpoint definitions for moderate and severe disease based on the framework provided by the WHO 2009 classification.

Methods

The endpoints were first proposed and discussed in a structured expert consultation. After that, the Delphi method was carried out to assess the usefulness, validity and feasibility of the standardized clinical disease endpoints for interventional dengue research.

Results

Most respondents (> 80%) agreed there is a need for both standardized clinical endpoints and operationalization of severe endpoints. Most respondents (67%) felt there is utility for moderate severity endpoints, but cited challenges in their development. Hospitalization as a moderate endpoint of disease severity or measure of public health impact was deemed to be useful by only 47% of respondents, but 89% felt it could bring about supplemental information if carefully contextualized according to data collection setting. Over half of the respondents favored alignment of the standard endpoints with the WHO guidelines (58%), but cautioned that the endpoints could have ramifications for public health practice. In terms of data granularity of the endpoints, there was a slight preference for a categorical vs numeric system (e.g. 1–10) (47% vs 34%), and 74% of respondents suggested validating the endpoints using large prospective data sets.

Conclusion

The structured consensus-building process was successful taking into account the history of the debate around potential endpoints for severe dengue. There is clear support for the development of standardized endpoints for interventional clinical research and the need for subsequent validation with prospective data sets. Challenges include the complexity of developing moderate disease research endpoints for dengue.

Development of standard clinical endpoints for use in dengue interventional trials

Dengue is a major public health problem worldwide. Although several drug candidates have been evaluated in randomized controlled trials, none has been effective and at present, early recognition of severe dengue and timely supportive care are used to reduce mortality. While the first dengue vaccine was recently licensed, and several other candidates are in late stage clinical trials, future decisions regarding widespread deployment of vaccines and/or therapeutics will require evidence of product safety, efficacy and effectiveness. Standard, quantifiable clinical endpoints are needed to ensure reproducibility and comparability of research findings. To address this need, we established a working group of dengue researchers and public health specialists to develop standardized endpoints and work towards consensus opinion on those endpoints. After discussion at two working group meetings and presentations at international conferences, a Delphi methodology-based query was used to finalize and operationalize the clinical endpoints. Participants were asked to select the best endpoints from proposed definitions or offer revised/new definitions, and to indicate whether contributing items should be designated as optional or required. After the third round of inquiry, 70% or greater agreement was reached on moderate and severe plasma leakage, moderate and severe bleeding, acute hepatitis and acute liver failure, and moderate and severe neurologic disease. There was less agreement regarding moderate and severe thrombocytopenia and moderate and severe myocarditis. Notably, 68% of participants agreed that a 50,000 to 20,000 mm³ platelet range be used to define moderate thrombocytopenia; however, they remained divided on whether a rapid decreasing trend or one platelet count should be case defining. While at least 70% agreement was reached on most endpoints, the process identified areas for further evaluation and standardization within the context of ongoing clinical studies. These endpoints can be used to harmonize data collection and improve comparability between dengue clinical trials.

Dengue is a major public health problem worldwide. Although several drug candidates have been evaluated in randomized controlled trials, none has been effective, and early recognition of severe dengue and timely supportive care remain the only means to reduce mortality. While the first dengue vaccine was recently licensed, and several other candidates are in late stage clinical trials, future decisions regarding deployment of such vaccines or therapeutics will require evidence of product safety, efficacy and effectiveness. Standard, quantifiable clinical endpoints are needed to ensure reproducibility and comparability of research findings. To address this need, we established a working group of dengue researchers, vaccine developers, and public health specialists to develop endpoints. After two working group meetings and discussions at international meetings, the Delphi methodology was used to clarify and further develop endpoints such that 70% or greater agreement was reached on most endpoint definitions including moderate and severe plasma leakage, moderate and severe bleeding, acute hepatitis and acute liver failure, and moderate and severe neurologic disease. The process identified areas for further evaluation and standardization within the context of ongoing clinical studies. The endpoints can be used to harmonize data collection and improve comparability between dengue clinical trials.

Development of a Prognostic Prediction Model to Determine Severe Dengue in Children

OBJECTIVE

To develop a prognostic prediction model using the seven warning signs highlighted by WHO revised Dengue fever classification 2009 to determine severe dengue in children.

METHODS

In this prospective analytical study conducted in a tertiary care centre, consecutive sampling of all children aged 1mo to 12y admitted with serologically confirmed Dengue was done from May 2015 through August 2016. After excluding 27 patients with co-infections and co-morbidities, 359 patients were followed up daily to assess clinical and laboratory progression till discharge/ death. Independent predictors were abdominal pain or tenderness, persistent vomiting, lethargy, mucosal bleed, clinical fluid accumulation, hepatomegaly >2 cm and rising hematocrit concurrent with platelet count <100 × 10⁹/L. Outcome measure was severe dengue defined as per WHO guidelines 2009.

RESULTS

Among 359 children, 93 progressed to severe dengue. In univariate analysis, significant predictors were clinical fluid accumulation (OR 4.773, p = 0.000, 95%CI 2.511-9.075), persistent vomiting (OR 1.944, p = 0.010, 95%CI 1.170-3.225), mucosal bleed (OR 2.045, p = 0.019, 95%CI 1.127-3.711) and hematocrit ≥0.40 concurrent with platelet count <100 × 10⁹/L (OR 2.985, p = 0.000, 95%CI 1.783-4.997). The final multivariable model included clinical fluid accumulation (aOR 3.717, p = 0.000, 95%CI 1.901-7.269), hematocrit ≥0.40 concurrent with platelet count <100 × 10⁹/L (aOR 2.252, p = 0.004, 95%CI 1.302-3.894) and persistent vomiting (p = 0.056) as predictors of severe dengue.

CONCLUSIONS

Among seven WHO warning signs, predictors of severe dengue as suggested by the present multivariable prediction model include clinical fluid accumulation, persistent vomiting and hematocrit ≥0.40 concurrent with platelet count <100 × 10⁹/L.

A New Look at an Old Disease: Recent Insights into the Global Epidemiology of Dengue

PURPOSE OF REVIEW

By all measures, the morbidity and mortality due to dengue are continuing to worsen worldwide. Although both early and recent studies have demonstrated regional differences in how dengue affects local populations, these findings were to varying extents related to disparate surveillance approaches.

RECENT FINDINGS

Recent studies have broadened the recognized spectrum of disease resulting from DENV infection, particularly in adults, and have also demonstrated new mechanisms of DENV spread both within and between populations. New results regarding the frequency and duration of homo- and heterotypic anti-DENV antibodies have provided important insights relevant to vaccine design and implementation.

SUMMARY

These observations and findings as well as difficulties in comparing the epidemiology of dengue within and between regions of the world underscore the need for population-based dengue surveillance worldwide. Enhanced surveillance should be implemented to complement passive surveillance in countries in the tropics to establish baseline data in order to define affected populations and evaluate the impact of dengue vaccines and novel vector control interventions.

Dengue infection

Dengue is widespread throughout the tropics and local spatial variation in dengue virus transmission is strongly influenced by rainfall, temperature, urbanization and distribution of the principal mosquito vector Aedes aegypti. Currently, endemic dengue virus transmission is reported in the Eastern Mediterranean, American, South-East Asian, Western Pacific and African regions, whereas sporadic local transmission has been reported in Europe and the United States as the result of virus introduction to areas where Ae. aegypti and Aedes albopictus, a secondary vector, occur. The global burden of the disease is not well known, but its epidemiological patterns are alarming for both human health and the global economy. Dengue has been identified as a disease of the future owing to trends toward increased urbanization, scarce water supplies and, possibly, environmental change. According to the WHO, dengue control is technically feasible with coordinated international technical and financial support for national programmes. This Primer provides a general overview on dengue, covering epidemiology, control, disease mechanisms, diagnosis, treatment and research priorities.

Knowledge, attitudes, and practices regarding dengue infection among public sector healthcare providers in Machala, Ecuador

Background

Dengue fever is a rapidly emerging infection throughout the tropics and subtropics with extensive public health burden. Adequate training of healthcare providers is crucial to reducing infection incidence through patient education and collaboration with public health authorities. We examined how public sector healthcare providers in a dengue-endemic region of Ecuador view and manage dengue infections, with a focus on the 2009 World Health Organization (WHO) Dengue Guidelines.

Methods

A 37-item questionnaire of dengue knowledge, attitudes, and practices was developed and administered to dengue healthcare providers in Machala, Ecuador. Survey focus areas included: “Demographics,” “Infection and Prevention of Dengue,” “Dengue Diagnosis and the WHO Dengue Guide,” “Laboratory Testing,” “Treatment of Dengue,” and “Opinions Regarding Dengue.”

Results

A total of 76 healthcare providers participated in this study, of which 82 % were medical doctors and 14 % were nurses. Fifty-eight percent of healthcare professionals practiced in ambulatory clinics and 34 % worked in a hospital. Eighty-nine percent of respondents were familiar with the 2009 WHO Dengue Guidelines, and, within that group, 97 % reported that the WHO Dengue Guide was helpful in dengue diagnosis and clinical management. Knowledge gaps identified included Aedes aegypti mosquito feeding habits and dengue epidemiology. Individuals with greater dengue-related knowledge were more likely to consider dengue a major health problem. Only 22 % of respondents correctly reported that patients with comorbidities and dengue without warning signs require hospital admission, and 25 % of providers reported never admitting patients with dengue to the hospital. Twenty percent of providers reported rarely (≤25 % of cases) obtaining laboratory confirmation of dengue infection. Providers reported patient presumptive self-medication as an ongoing problem. Thirty-one percent of healthcare providers reported inadequate access to resources needed to diagnose and treat dengue.

Conclusion

Participants demonstrated a high level of knowledge of dengue symptoms and treatment, but additional training regarding prevention, diagnosis, and admission criteria is needed. Interventions should not only focus on increasing knowledge, but also encourage review of the WHO Dengue Guidelines, avoidance of presumptive self-medication, and recognition of dengue as a major health problem. This study provided an assessment tool that effectively captured healthcare providers’ knowledge and identified critical gaps in practice.

Electronic supplementary material

The online version of this article (doi:10.1186/s40794-016-0024-y) contains supplementary material, which is available to authorized users.

Recent advances in dengue pathogenesis and clinical management

This review describes and commentates on recent advances in the understanding of dengue pathogenesis and immunity, plus clinical research on vaccines and therapeutics. We expand specifically on the role of the dermis in dengue virus infection, the contribution of cellular and humoral immune responses to pathogenesis and immunity, NS1 and mechanisms of virus immune evasion. Additionally we review a series of therapeutic intervention trials for dengue, as well as recent clinical research aimed at improving clinical diagnosis, risk prediction and disease classification.

Reviewing dengue: still a neglected tropical disease?

Dengue is currently listed as a “neglected tropical disease” (NTD). But is dengue still an NTD or not? Classifying dengue as an NTD may carry advantages, but is it justified? This review considers the criteria for the definition of an NTD, the current diverse lists of NTDs by different stakeholders, and the commonalities and differences of dengue with other NTDs. We also review the current research gaps and research activities and the adequacy of funding for dengue research and development (R&D) (2003–2013). NTD definitions have been developed to a higher precision since the early 2000s, with the following main features: NTDs are characterised as a) poverty related, b) endemic to the tropics and subtropics, c) lacking public health attention, d) having poor research funding and shortcomings in R&D, e) usually associated with high morbidity but low mortality, and f) often having no specific treatment available. Dengue meets most of these criteria, but not all. Although dengue predominantly affects resource-limited countries, it does not necessarily only target the poor and marginalised in those countries. Dengue increasingly attracts public health attention, and in some affected countries it is now a high profile disease. Research funding for dengue has increased exponentially in the past two decades, in particular in the area of dengue vaccine development. However, despite advances in dengue research, dengue epidemics are increasing in frequency and magnitude, and dengue is expanding to new areas. Specific treatment and a highly effective vaccine remain elusive. Major research gaps exist in the area of integrated surveillance and vector control. Hence, although dengue differs from many of the NTDs, it still meets important criteria commonly used for NTDs. The current need for increased R&D spending, shared by dengue and other NTDs, is perhaps the key reason why dengue should continue to be considered an NTD.

Evaluation of host and viral factors associated with severe dengue based on the 2009 WHO classification

BACKGROUND

Dengue fever (DF) is the most prevalent arthropod-borne viral disease affecting humans. The World Health Organization (WHO) proposed a revised classification in 2009 to enable the more effective identification of cases of severe dengue (SD). This was designed primarily as a clinical tool, but it also enables cases of SD to be differentiated into three specific subcategories (severe vascular leakage, severe bleeding, and severe organ dysfunction). However, no study has addressed whether this classification has advantage in estimating factors associated with the progression of disease severity or dengue pathogenesis. We evaluate in a dengue outbreak associated risk factors that could contribute to the development of SD according to the 2009 WHO classification.

METHODS

A prospective cross-sectional study was performed during an epidemic of dengue in 2009 in Chiapas, Mexico. Data were analyzed for host and viral factors associated with dengue cases, using the 1997 and 2009 WHO classifications. The cost-benefit ratio (CBR) was also estimated.

RESULTS

The sensitivity in the 1997 WHO classification for determining SD was 75%, and the specificity was 97.7%. For the 2009 scheme, these were 100% and 81.1%, respectively. The 2009 classification showed a higher benefit (537%) with a lower cost (10.2%) than the 1997 WHO scheme. A secondary antibody response was strongly associated with SD. Early viral load was higher in cases of SD than in those with DF. Logistic regression analysis identified predictive SD factors (secondary infection, disease phase, viral load) within the 2009 classification. However, within the 1997 scheme it was not possible to differentiate risk factors between DF and dengue hemorrhagic fever or dengue shock syndrome. The critical clinical stage for determining SD progression was the transition from fever to defervescence in which plasma leakage can occur.

CONCLUSIONS

The clinical phenotype of SD is influenced by the host (secondary response) and viral factors (viral load). The 2009 WHO classification showed greater sensitivity to identify SD in real time. Timely identification of SD enables accurate early decisions, allowing proper management of health resources for the benefit of patients at risk for SD. This is possible based on the 2009 WHO classification.

Approaches to refining estimates of global burden and economics of dengue

Dengue presents a formidable and growing global economic and disease burden, with around half the world's population estimated to be at risk of infection. There is wide variation and substantial uncertainty in current estimates of dengue disease burden and, consequently, on economic burden estimates. Dengue disease varies across time, geography and persons affected. Variations in the transmission of four different viruses and interactions among vector density and host's immune status, age, pre-existing medical conditions, all contribute to the disease's complexity. This systematic review aims to identify and examine estimates of dengue disease burden and costs, discuss major sources of uncertainty, and suggest next steps to improve estimates. Economic analysis of dengue is mainly concerned with costs of illness, particularly in estimating total episodes of symptomatic dengue. However, national dengue disease reporting systems show a great diversity in design and implementation, hindering accurate global estimates of dengue episodes and country comparisons. A combination of immediate, short-, and long-term strategies could substantially improve estimates of disease and, consequently, of economic burden of dengue. Suggestions for immediate implementation include refining analysis of currently available data to adjust reported episodes and expanding data collection in empirical studies, such as documenting the number of ambulatory visits before and after hospitalization and including breakdowns by age. Short-term recommendations include merging multiple data sources, such as cohort and surveillance data to evaluate the accuracy of reporting rates (by health sector, treatment, severity, etc.), and using covariates to extrapolate dengue incidence to locations with no or limited reporting. Long-term efforts aim at strengthening capacity to document dengue transmission using serological methods to systematically analyze and relate to epidemiologic data. As promising tools for diagnosis, vaccination, vector control, and treatment are being developed, these recommended steps should improve objective, systematic measures of dengue burden to strengthen health policy decisions.

Comparing the usefulness of the 1997 and 2009 WHO dengue case classification: a systematic literature review

The 1997 and 2009 WHO dengue case classifications were compared in a systematic review with 12 eligible studies (4 prospective). Ten expert opinion articles were used for discussion. For the 2009 WHO classification studies show: when determining severe dengue sensitivity ranges between 59-98% (88%/98%: prospective studies), specificity between 41-99% (99%: prospective study) - comparing the 1997 WHO classification: sensitivity 24.8-89.9% (24.8%/74%: prospective studies), specificity: 25%/100% (100%: prospective study). The application of the 2009 WHO classification is easy, however for (non-severe) dengue there may be a risk of monitoring increased case numbers. Warning signs validation studies are needed. For epidemiological/pathogenesis research use of the 2009 WHO classification, opinion papers show that ease of application, increased sensitivity (severe dengue) and international comparability are advantageous; 3 severe dengue criteria (severe plasma leakage, severe bleeding, severe organ manifestation) are useful research endpoints. The 2009 WHO classification has clear advantages for clinical use, use in epidemiology is promising and research use may at least not be a disadvantage.

Clinical presentation of dengue by serotype and year of epidemic in Martinique

During the last decade Martinique experienced four dengue epidemics, each characterized by the predominance of 1 or 2 serotypes. In this retrospective database analysis, we investigated the relationship between dengue serotype and disease severity. Data on dengue were collected from 715 patients (male/female ratio 0.87), 14 to 91 years of age (median 35 years) examined in the adult emergency department between 2005 and 2010. In this series, DENV-4 infections more frequently had a milder clinical presentation. The DENV-2 infections were most often secondary infections admitted at the critical phase of dengue illness with signs of plasma leakage. The DENV-1 infections were disabling, particularly in females, and most often led to disease of intermediate severity, without overt plasma leakage. These data were consistent with there being differences in virulence between serotypes, regardless of the host's immune status. However, secondary DENV-2 infections showed an increased risk of plasma leakage.

Comparative performance of the probable case definitions of dengue by WHO (2009) and the WHO-SEAR expert group (2011)

BACKGROUND

The primary objective of this study was to find the performance of the 2009 probable case definition of dengue and compare it with the definition given by the WHO-SEAR expert group in 2011.

METHODS

A cross-sectional study was conducted in Thiruvananthapuram district of Kerala, which is hyperendemic for dengue. A consecutive series of 851 participants defined by the selection criteria were recruited from the primary, secondary, and tertiary health care settings. Sensitivity, specificity, predictive values, and likelihood ratios of the clinical case definitions were calculated using reverse transcriptase-polymerized chain reaction (RT-PCR) as gold standard in case of fever less than or equal to 5 days and serology (IgM positivity) for fever >5 days. Diagnostic odds ratio (DOR) was also calculated as a single indicator of performance of the case definition.

RESULTS

The 2009 World Health Organization (WHO) case definition had a sensitivity of 76·4% (69·6-82·1) and negative predictive value of 87·5%. The 2011 WHO-SEAR expert group case definition had a higher sensitivity of 87·9% (82·2-91·9) but lower negative predictive value of 86·6%. The three independent criteria which were significantly associated with dengue were thrombocytopenia less than 150,000 (OR 2·80), leukopenia (OR 2·28), and absence of backache (OR 2·68). The performance of 2009 case definition was better (DOR 2·4) than the 2011 WHO-SEAR expert group case definition. This was further enhanced when thrombocytopenia was specified as platelet count less than 150,000 (DOR2·7). When 'no backahe' was added as an additional criteria, the performance of both definitions improved.

CONCLUSIONS

The 2009 WHO case definition has better discriminatory power than the 2011 WHO-SEAR expert group case definition. The performance of 2009 WHO case definition is enhanced by specifying thrombocytopenia as platelet count less than 150,000. The inclusion of 'no backache' further improves the discriminatory power. This may be more useful in primary care settings, to rule out dengue.