Secondary dengue serotype 1 infection causing dengue shock syndrome with rhombencephalitis and bleeding associated with refractory thrombocytopenia: A case report.

Background: Dengue has a wide spectrum of manifestations, from an asymptomatic condition to dengue shock syndrome. Extensive plasma leakage, severe bleeding, or both, could lead to dengue shock syndrome, a common cause of death in dengue-infected patients. Thrombocytopenia is a common laboratory finding in dengue, which correlates with the disease severity and rapidly resolves during the recovery phase. Therefore, refractory thrombocytopenia is rare in patients with dengue. Rhombencephalitis is an inflammatory disease affecting the hindbrain, rarely associated with dengue. We report the second case of dengue-associated rhombencephalitis, wherein the patient developed dengue shock syndrome and severe bleeding associated with refractory thrombocytopenia. Case report: A 47-year-old Thai female with secondary dengue serotype 1 infection developed dengue shock syndrome with rhombencephalitis, manifested as altered sensorium and status epilepticus in the critical phase. Cerebrospinal fluid analysis showed pleocytosis with predominantly mononuclear cells and high protein levels. Magnetic resonance imaging of the brain showed multifocal brain signal abnormalities involving the medulla oblongata, pons, midbrain, bilateral hippocampi, thalami, posterior limb of internal capsules, external capsules, and deep hemispheric white matter. The patient had partial neurological recovery following rhombencephalitis for one month. During the recovery phase, severe bleeding with refractory thrombocytopenia and acute kidney injury were observed. Methylprednisolone with eltrombopag was administered, which resulted in an increased the platelet count, cessation of bleeding and recovery of kidney function within 4 days. Conclusions: Dengue is a potential cause of rhombencephalitis. Dengue-associated rhombencephalitis develops during the critical phase, with only partial neurological recovery. However, severe bleeding and refractory thrombocytopenia were also observed during the recovery phase. Methylprednisolone with a thrombopoietin receptor agonist could be an effective treatment for increasing platelet count and stopping bleeding in dengue.

Predictors of plasma leakage among dengue patients in Thailand: A plasma-leak score analysis.

Delayed plasma leakage recognition could lead to improper fluid administration resulting in dengue shock syndrome, subsequently, multi-organ failure, and death. This prospective observational study was conducted in Bangkok, Thailand, between March 2018 and February 2020 to determine predictors of plasma leakage and develop a plasma leakage predictive score among dengue patients aged ≥15 years. Of 667 confirmed dengue patients, 318 (47.7%) developed plasma leakage, and 349 (52.3%) had no plasma leakage. Multivariate analysis showed three independent factors associated with plasma leakage, including body mass index ≥25.0 kg/m2 (odds ratio [OR] = 1.784; 95% confidence interval [CI] = 1.040-3.057; P = 0.035), platelet count <100,000/mm3 on fever days 3 to 4 (OR = 2.151; 95% CI = 1.269-3.647; P = 0.004), and aspartate aminotransferase or alanine aminotransferase ≥100 U/l on fever days 3 to 4 (OR = 2.189; 95% CI = 1.231-3.891; P = 0.008). Because these three parameters had evidence of equality, each independent factor was weighted to give a score of 1 with a total plasma-leak score of 3. Higher scores were associated with increased plasma leakage occurrence, with ORs of 2.017 (95% CI = 1.052-3.869; P = 0.035) for score 1, 6.158 (95% CI = 2.914-13.015; P <0.001) for score 2, and 6.300 (95% CI = 2.419-16.407; P <0.001) for score 3. The area under the receiver operating characteristics curves for predicting plasma leakage was good (0.677 [95% CI = 0.616-0.739]). Patients with a plasma-leak score ≥1 had high sensitivity (88.8%), and those with a plasma-leak score of 3 had high specificity (93.4%) for plasma leakage occurrence. This simple and easily accessible clinical score might help physicians provide early and timely appropriate clinical dengue management in endemic areas.

Risk predictors of progression to severe disease during the febrile phase of dengue: a systematic review and meta-analysis.

BACKGROUND: The ability to accurately predict early progression of dengue to severe disease is crucial for patient triage and clinical management. Previous systematic reviews and meta-analyses have found significant heterogeneity in predictors of severe disease due to large variation in these factors during the time course of the illness. We aimed to identify factors associated with progression to severe dengue disease that are detectable specifically in the febrile phase. METHODS: We did a systematic review and meta-analysis to identify predictors identifiable during the febrile phase associated with progression to severe disease defined according to WHO criteria. Eight medical databases were searched for studies published from Jan 1, 1997, to Jan 31, 2020. Original clinical studies in English assessing the association of factors detected during the febrile phase with progression to severe dengue were selected and assessed by three reviewers, with discrepancies resolved by consensus. Meta-analyses were done using random-effects models to estimate pooled effect sizes. Only predictors reported in at least four studies were included in the meta-analyses. Heterogeneity was assessed using the Cochrane Q and I2 statistics, and publication bias was assessed by Egger's test. We did subgroup analyses of studies with children and adults. The study is registered with PROSPERO, CRD42018093363. FINDINGS: Of 6643 studies identified, 150 articles were included in the systematic review, and 122 articles comprising 25 potential predictors were included in the meta-analyses. Female patients had a higher risk of severe dengue than male patients in the main analysis (2674 [16·2%] of 16 481 vs 3052 [10·5%] of 29 142; odds ratio [OR] 1·13 [95% CI 1·01-1·26) but not in the subgroup analysis of studies with children. Pre-existing comorbidities associated with severe disease were diabetes (135 [31·3%] of 431 with vs 868 [16·0%] of 5421 without; crude OR 4·38 [2·58-7·43]), hypertension (240 [35·0%] of 685 vs 763 [20·6%] of 3695; 2·19 [1·36-3·53]), renal disease (44 [45·8%] of 96 vs 271 [16·0%] of 1690; 4·67 [2·21-9·88]), and cardiovascular disease (nine [23·1%] of 39 vs 155 [8·6%] of 1793; 2·79 [1·04-7·50]). Clinical features during the febrile phase associated with progression to severe disease were vomiting (329 [13·5%] of 2432 with vs 258 [6·8%] of 3797 without; 2·25 [1·87-2·71]), abdominal pain and tenderness (321 [17·7%] of 1814 vs 435 [8·1%] of 5357; 1·92 [1·35-2·74]), spontaneous or mucosal bleeding (147 [17·9%] of 822 vs 676 [10·8%] of 6235; 1·57 [1·13-2·19]), and the presence of clinical fluid accumulation (40 [42·1%] of 95 vs 212 [14·9%] of 1425; 4·61 [2·29-9·26]). During the first 4 days of illness, platelet count was lower (standardised mean difference -0·34 [95% CI -0·54 to -0·15]), serum albumin was lower (-0·5 [-0·86 to -0·15]), and aminotransferase concentrations were higher (aspartate aminotransferase [AST] 1·06 [0·54 to 1·57] and alanine aminotransferase [ALT] 0·73 [0·36 to 1·09]) among individuals who progressed to severe disease. Dengue virus serotype 2 was associated with severe disease in children. Secondary infections (vs primary infections) were also associated with severe disease (1682 [11·8%] of 14 252 with vs 507 [5·2%] of 9660 without; OR 2·26 [95% CI 1·65-3·09]). Although the included studies had a moderate to high risk of bias in terms of study confounding, the risk of bias was low to moderate in other domains. Heterogeneity of the pooled results varied from low to high on different factors. INTERPRETATION: This analysis supports monitoring of the warning signs described in the 2009 WHO guidelines on dengue. In addition, testing for infecting serotype and monitoring platelet count and serum albumin, AST, and ALT concentrations during the febrile phase of illness could improve the early prediction of severe dengue. FUNDING: Wellcome Trust, National Institute for Health Research, Collaborative Project to Increase Production of Rural Doctors, and Royal Thai Government.

Major Histocompatibility Complex Class I Chain-Related A and B (MICA and MICB) Gene, Allele, and Haplotype Associations With Dengue Infections in Ethnic Thais.

BACKGROUND: Major histocompatibility complex class I chain-related (MIC) A and B (MICA and MICB) are polymorphic stress molecules recognized by natural killer cells. This study was performed to analyze MIC gene profiles in hospitalized Thai children with acute dengue illness. METHODS: MIC allele profiles were determined in a discovery cohort of patients with dengue fever or dengue hemorrhagic fever (DHF) (n = 166) and controls (n = 149). A replication cohort of patients with dengue (n = 222) was used to confirm specific MICB associations with disease. RESULTS: MICA*045 and MICB*004 associated with susceptibility to DHF in secondary dengue virus (DENV) infections (odds ratio [OR], 3.22; [95% confidence interval (CI), 1.18-8.84] and 1.99 [1.07-2.13], respectively), and MICB*002 with protection from DHF in secondary DENV infections (OR, 0.41; 95% CI, .21-.68). The protective effect of MICB*002 against secondary DHF was confirmed in the replication cohort (OR, 0.43; 95% CI, .22-.82) and was stronger when MICB*002 is present in individuals also carrying HLA-B*18, B*40, and B*44 alleles which form the B44 supertype of functionally related alleles (0.29, 95% CI, .14-.60). CONCLUSIONS: Given that MICB*002 is a low expresser of soluble proteins, these data indicate that surface expression of MICB*002 with B44 supertype alleles on DENV-infected cells confer a protective advantage in controlling DENV infection using natural killer cells.

Use of structural equation models to predict dengue illness phenotype.

BACKGROUND: Early recognition of dengue, particularly patients at risk for plasma leakage, is important to clinical management. The objective of this study was to build predictive models for dengue, dengue hemorrhagic fever (DHF), and dengue shock syndrome (DSS) using structural equation modelling (SEM), a statistical method that evaluates mechanistic pathways. METHODS/FINDINGS: We performed SEM using data from 257 Thai children enrolled within 72 h of febrile illness onset, 156 with dengue and 101 with non-dengue febrile illnesses. Models for dengue, DHF, and DSS were developed based on data obtained three and one day(s) prior to fever resolution (fever days -3 and -1, respectively). Models were validated using data from 897 subjects who were not used for model development. Predictors for dengue and DSS included age, tourniquet test, aspartate aminotransferase, and white blood cell, % lymphocytes, and platelet counts. Predictors for DHF included age, aspartate aminotransferase, hematocrit, tourniquet test, and white blood cell and platelet counts. The models showed good predictive performances in the validation set, with area under the receiver operating characteristic curves (AUC) at fever day -3 of 0.84, 0.67, and 0.70 for prediction of dengue, DHF, and DSS, respectively. Predictive performance was comparable using data based on the timing relative to enrollment or illness onset, and improved closer to the critical phase (AUC 0.73 to 0.94, 0.61 to 0.93, and 0.70 to 0.96 for dengue, DHF, and DSS, respectively). CONCLUSIONS: Predictive models developed using SEM have potential use in guiding clinical management of suspected dengue prior to the critical phase of illness.

Activation of Peripheral T Follicular Helper Cells During Acute Dengue Virus Infection.

Background: Follicular helper T cells (TFH) are specialized CD4 T cells required for B-cell help and antibody production. Methods: Given the postulated role of immune activation in dengue disease, we measured the expansion and activation of TFH in the circulation (peripheral TFH [pTFH]) collected from Thai children with laboratory-confirmed acute dengue virus (DENV) infection. Results: We found significant expansion and activation of pTFH subsets during acute infection with the highest frequencies of activated pTFH (PD1hi pTFH and PD1+CD38+ pTFH) detected during the critical phase of illness. Numbers of activated pTFH were higher in patients with secondary compared with primary infections and in patients with more severe disease. We also found a positive correlation between the frequencies of activated pTFH and the frequencies of plasmablasts. Conclusions: To our knowledge, this is the first ex vivo analysis of pTFH activation during acute DENV infection. Overall, our study supports the model that pTFH contribute to disease evolution during the critical stage of illness.

Case Management of Dengue: Lessons Learned.

The global burden of dengue and its geographic distribution have increased over the past several decades. The introduction of dengue in new areas has often been accompanied by high case-fatality rates. Drawing on the experience in managing dengue cases at the Queen Sirikit National Institute of Child Health in Bangkok, Thailand, this article provides the authors' perspectives on key clinical lessons to improve dengue-related outcomes. Parallels between this clinical experience and outcomes reported in randomized controlled trials, results of efforts to disseminate practice recommendations, and suggestions for areas for further research are also discussed.

Dengue diversity across spatial and temporal scales: Local structure and the effect of host population size.

A fundamental mystery for dengue and other infectious pathogens is how observed patterns of cases relate to actual chains of individual transmission events. These pathways are intimately tied to the mechanisms by which strains interact and compete across spatial scales. Phylogeographic methods have been used to characterize pathogen dispersal at global and regional scales but have yielded few insights into the local spatiotemporal structure of endemic transmission. Using geolocated genotype (800 cases) and serotype (17,291 cases) data, we show that in Bangkok, Thailand, 60% of dengue cases living <200 meters apart come from the same transmission chain, as opposed to 3% of cases separated by 1 to 5 kilometers. At distances <200 meters from a case (encompassing an average of 1300 people in Bangkok), the effective number of chains is 1.7. This number rises by a factor of 7 for each 10-fold increase in the population of the "enclosed" region. This trend is observed regardless of whether population density or area increases, though increases in density over 7000 people per square kilometer do not lead to additional chains. Within Thailand these chains quickly mix, and by the next dengue season viral lineages are no longer highly spatially structured within the country. In contrast, viral flow to neighboring countries is limited. These findings are consistent with local, density-dependent transmission and implicate densely populated communities as key sources of viral diversity, with home location the focal point of transmission. These findings have important implications for targeted vector control and active surveillance.

Synchrony of Dengue Incidence in Ho Chi Minh City and Bangkok.

BACKGROUND: Ho Chi Minh City and Bangkok are highly dengue endemic. The extent to which disease patterns are attributable to local versus regional dynamics remains unclear. To address this gap we compared key transmission parameters across the locations. METHODS AND PRINCIPAL FINDINGS: We used 2003-2009 age-stratified case data to inform catalytic transmission models. Further, we compared the spatial clustering of serotypes within each city. We found that annual case numbers were highly consistent across the two cities (correlation of 0.77, 95% CI: 0.74-0.79) as was the annual force of infection (correlation of 0.57, 95% CI: 0.46-0.68). Serotypes were less similar with serotype-specific correlations ranging from 0.65 for DENV1 to -0.14 for DENV4. Significant spatial clustering of serotypes was observed in HCMC at distances <500m, similar to previous observations from Bangkok. DISCUSSIONS: Dengue dynamics are comparable across these two hubs. Low correlation in serotype distribution suggests that similar built environments, vector populations and climate, rather than viral flow drives these observations.

State-of-the-art monitoring in treatment of dengue shock syndrome: a case series.

BACKGROUND: Early recognition and treatment of circulatory volume loss is essential in the clinical management of dengue viral infection. We hypothesized that a novel computational algorithm, originally developed for noninvasive monitoring of blood loss in combat casualties, could: (1) indicate the central volume status of children with dengue during the early stages of "shock"; and (2) track fluid resuscitation status. METHODS: Continuous noninvasive photoplethysmographic waveforms were collected over a 5-month period from three children of Thai ethnicity with clinical suspicion of dengue. Waveform data were processed by the algorithm to calculate each child's Compensatory Reserve Index, where 1 represents supine normovolemia and 0 represents the circulatory volume at which hemodynamic decompensation occurs. Values between 1 and 0 indicate the proportion of reserve remaining before hemodynamic decompensation. RESULTS: This case report describes a 7-year-old Thai boy, another 7-year-old Thai boy, and a 9-year-old Thai boy who exhibited signs and symptoms of dengue shock syndrome; all the children had secondary dengue virus infections, documented by serology and reverse transcriptase polymerase chain reaction. The three boys experienced substantial plasma leakage demonstrated by pleural effusion index >25, ascites, and >20 % hemoconcentration. They received fluid administered intravenously; one received a blood transfusion. All three boys showed a significantly low initial Compensatory Reserve Index (≥0.20), indicating a clinical diagnosis of "near shock". Following 5 days with fluid resuscitation treatment, their Compensatory Reserve Index increased towards "normovolemia" (that is, Compensatory Reserve Index >0.75). CONCLUSIONS: The results from these cases demonstrate a new variation in the diagnostic capability to manage patients with dengue shock syndrome. The findings shed new light on a method that can avoid possible adverse effects of shock by noninvasive measurement of a patient's compensatory reserve rather than standard vital signs or invasive diagnostic methods.

Forty Years of Dengue Surveillance at a Tertiary Pediatric Hospital in Bangkok, Thailand, 1973-2012.

Long-term observational studies can provide valuable insights into overall dengue epidemiology. Here, we present analysis of dengue cases at a pediatric hospital in Bangkok, Thailand, during a 40-year period from 1973 to 2012. Data were analyzed from 25,715 hospitalized patients with laboratory-confirmed dengue virus (DENV) infection. Several long-term trends in dengue disease were identified including an increase in mean age of hospitalized cases from an average of 7-8 years, an increase after 1990 in the proportion of post-primary cases for DENV-1 and DENV-3, and a decrease in the proportion of dengue hemorrhagic fever and dengue shock syndrome cases in primary and post-primary cases over time. Exploratory mechanistic analysis of these observed trends considered changes in diagnostic methods, demography, force of infection, and Japanese encephalitis vaccination as possible explanations. Thailand is an important setting for studying DENV transmission as it has a "mature" dengue epidemiology with a strong surveillance system in place since the early 1970s. We characterized changes in dengue epidemiology over four decades, and possible impact of demographic and other changes in the human population. These results may inform other countries where similar changes in transmission and population demographics may now or may soon be occurring.

Dengue Virus (DENV) Neutralizing Antibody Kinetics in Children After Symptomatic Primary and Postprimary DENV Infection.

The immune response to dengue virus (DENV) infection is complex and not fully understood. Using longitudinal data from 181 children with dengue in Thailand who were followed for up to 3 years, we describe neutralizing antibody kinetics following symptomatic DENV infection. We observed that antibody titers varied by serotype, homotypic vs heterotypic responses, and primary versus postprimary infections. The rates of change in antibody titers over time varied between primary and postprimary responses. For primary infections, titers increased from convalescence to 6 months. By comparing homotypic and heterotypic antibody titers, we saw an increase in type specificity from convalescence to 6 months for primary DENV3 infections but not primary DENV1 infections. In postprimary cases, there was a decrease in titers from convalescence up until 6 months after infection. Beginning 1 year after both primary and postprimary infections, there was evidence of increasing antibody titers, with greater increases in children with lower titers, suggesting that antibody titers were boosted due to infection and that higher levels of neutralizing antibody may be more likely to confer a sterilizing immune response. These findings may help to model virus transmission dynamics and provide baseline data to support the development of vaccines and therapeutics.

Epidemiology of Infant Dengue Cases Illuminates Serotype-Specificity in the Interaction between Immunity and Disease, and Changes in Transmission Dynamics.

BACKGROUND: Infants born to dengue immune mothers acquire maternal antibodies to dengue. These antibodies, though initially protective, decline during the first year of life to levels thought to be disease enhancing, before reaching undetectable levels. Infants have long been studied to understand the interaction between infection and disease on an individual level. METHODS/FINDINGS: Considering infants (cases <1 year old) as a unique group, we analyzed serotype specific dengue case data from patients admitted to a pediatric hospital in Bangkok, Thailand. We show differences in the propensity of serotypes to cause disease in individuals with dengue antibodies (infants and post-primary cases) and in individuals without dengue antibodies (primary cases). The mean age of infant cases differed among serotypes, consistent with previously observed differential waning of maternal antibody titers by serotype. We show that trends over time in epidemiology of infant cases are consistent with those observed in the whole population, and therefore with trends in the force of infection. CONCLUSIONS/SIGNIFICANCE: Infants with dengue are informative about the interaction between antibody and the dengue serotypes, confirming that in this population DENV-2 and DENV-4 almost exclusively cause disease in the presence of dengue antibody despite infections occurring in others. We also observe differences between the serotypes in the mean age in infant cases, informative about the interaction between waning immunity and disease for the different serotypes in infants. In addition, we show that the mean age of infant cases over time is informative about transmission in the whole population. Therefore, ongoing surveillance for dengue in infants could provide useful insights into dengue epidemiology, particularly after the introduction of a dengue vaccine targeting adults and older children.

Evaluation of Cardiac Involvement in Children with Dengue by Serial Echocardiographic Studies.

BACKGROUND: Infection with dengue virus results in a wide range of clinical manifestations from dengue fever (DF), a self-limited febrile illness, to dengue hemorrhagic fever (DHF) which is characterized by plasma leakage and bleeding tendency. Although cardiac involvement has been reported in dengue, the incidence and the extent of cardiac involvement are not well defined. METHODS AND PRINCIPAL FINDINGS: We characterized the incidence and changes in cardiac function in a prospective in-patient cohort of suspected dengue cases by serial echocardiography. Plasma leakage was detected by serial chest and abdominal ultrasonography. Daily cardiac troponin-T levels were measured. One hundred and eighty one dengue cases were enrolled. On the day of enrollment, dengue cases that already developed plasma leakage had lower cardiac index (2695 (127) vs 3188 (75) (L/min/m2), p = .003) and higher left ventricular myocardial performance index (.413 (.021) vs .328 (.026), p = .021) and systemic vascular resistance (2478 (184) vs 1820 (133) (dynes·s/cm5), p = .005) compared to those without plasma leakage. Early diastolic wall motion of the left ventricle was decreased in dengue cases with plasma leakage compared to those without. Decreased left ventricular wall motility was more common in dengue patients compared to non-dengue cases particularly in cases with plasma leakage. Differences in cardiac function between DF and DHF were most pronounced around the time of plasma leakage. Cardiac dysfunction was transient and did not require treatment. Transient elevated troponin-T levels were more common in DHF cases compared to DF (14.5% vs 5%, p = 0.028). CONCLUSIONS: Transient left ventricular systolic and diastolic dysfunction was common in children hospitalized with dengue and related to severity of plasma leakage. The functional abnormality spontaneously resolved without specific treatment. Cardiac structural changes including myocarditis were uncommon.

Evolutionary relationship of 5'-untranslated regions among Thai dengue-3 viruses, Bangkok isolates, during 24 year-evolution.

OBJECTIVE: To study evolutionary relationship of the 5'untranslated regions (5'UTRs) in low passage dengue3 viruses (DEN3) isolated from hospitalized children with different clinical manifestations in Bangkok during 24 year-evolution (1977-2000) comparing to the DEN3 prototype (H87). METHODS: The 5'UTRs of these Thai DEN3 and the H87 prototype were amplified by RT-PCR and sequenced. Their multiple sequence alignments were done by Codon Code Aligner v 4.0.4 software and their RNA secondary structures were predicted by MFOLD software. Replication of five Thai DEN3 candidates comparing to the H87 prototype were done in human (HepG2) and the mosquito (C6/36) cell lines. RESULTS: Among these Thai DEN3, the completely identical sequences of their first 89 nucleotides, their high-order secondary structure of 5'UTRs and three SNPs including the predominant C90T, and two minor SNPs including A109G and A112G were found. The C90T of Thai DEN3, Bangkok isolates was shown predominantly before 1977. Five Thai DEN3 candidates with the predominant C90T were shown to replicate in human (HepG2) and the mosquito (C6/36) cell lines better than the H87 prototype. However, their highly conserved sequences as well as SNPs of the 5'UTR did not appear to correlate with their disease severity in human. CONCLUSIONS: Our findings highlighted evolutionary relationship of the completely identical 89 nucleotide sequence, the high-order secondary structure and the predominant C90T of the 5'UTR of these Thai DEN3 during 24 year-evolution further suggesting to be their genetic markers and magic targets for future research on antiviral therapy as well as vaccine approaches of Thai DEN3.

Sequential dengue virus infections detected in active and passive surveillance programs in Thailand, 1994-2010.

BACKGROUND: The effect of prior dengue virus (DENV) exposure on subsequent heterologous infection can be beneficial or detrimental depending on many factors including timing of infection. We sought to evaluate this effect by examining a large database of DENV infections captured by both active and passive surveillance encompassing a wide clinical spectrum of disease. METHODS: We evaluated datasets from 17 years of hospital-based passive surveillance and nine years of cohort studies, including clinical and subclinical DENV infections, to assess the outcomes of sequential heterologous infections. Chi square or Fisher's exact test was used to compare proportions of infection outcomes such as disease severity; ANOVA was used for continuous variables. Multivariate logistic regression was used to assess risk factors for infection outcomes. RESULTS: Of 38,740 DENV infections, two or more infections were detected in 502 individuals; 14 had three infections. The mean ages at the time of the first and second detected infections were 7.6 ± 3.0 and 11.2 ± 3.0 years. The shortest time between sequential infections was 66 days. A longer time interval between sequential infections was associated with dengue hemorrhagic fever (DHF) in the second detected infection (OR 1.3, 95% CI 1.2-1.4). All possible sequential serotype pairs were observed among 201 subjects with DHF at the second detected infection, except DENV-4 followed by DENV-3. Among DENV infections detected in cohort subjects by active study surveillance and subsequent non-study hospital-based passive surveillance, hospitalization at the first detected infection increased the likelihood of hospitalization at the second detected infection. CONCLUSIONS: Increasing time between sequential DENV infections was associated with greater severity of the second detected infection, supporting the role of heterotypic immunity in both protection and enhancement. Hospitalization was positively associated between the first and second detected infections, suggesting a possible predisposition in some individuals to more severe dengue disease.

HLA Class I Supertype Associations With Clinical Outcome of Secondary Dengue Virus Infections in Ethnic Thais.

BACKGROUND: Human leukocyte antigen (HLA) supertypes are groups of functionally related alleles that present structurally similar antigens to the immune system. OBJECTIVES: To analyze HLA class I supertype associations with clinical outcome in hospitalized Thai children with acute dengue illness. METHODS: Seven hundred sixty-two patients and population-matched controls recruited predominantly in Bangkok were HLA-A and -B typed. HLA supertype frequencies were compared and tested for significant dengue disease associations using logistic regression analyses. Multivariable models were built by conducting forward stepwise selection procedures. RESULTS: In the final logistic regression model, the HLA-B44 supertype was protective against dengue hemorrhagic fever (DHF) in secondary infections (odds ratio [OR] = 0.46, 95% confidence interval [CI], .30-.72), while the HLA-A02 supertype (OR = 1.92, 95% CI, 1.30-2.83) and the HLA-A01/03 supertype (OR = 3.01, 95% CI, 1.01-8.92) were associated with susceptibility to secondary dengue fever. The B07 supertype was associated with susceptibility to secondary DHF in the univariate analysis (OR = 1.60, 95% CI, 1.05-2.46), whereas that was not retained in the final model. CONCLUSIONS: As the HLA-B44 supertype is predicted to target conserved epitopes in dengue, our results suggest that B44 supertype-restricted immune responses to highly conserved regions of the dengue proteome may protect against secondary DHF.

Monitoring and improving the sensitivity of dengue nested RT-PCR used in longitudinal surveillance in Thailand.

BACKGROUND: AFRIMS longitudinal dengue surveillance in Thailand depends on the nested RT-PCR and the dengue IgM/IgG ELISA. OBJECTIVE: To examine and improve the sensitivity of the nested RT-PCR using a panel of archived samples collected during dengue surveillance. STUDY DESIGN: A retrospective analysis of 16,454 dengue IgM/IgG ELISA positive cases collected between 2000 and 2013 was done to investigate the sensitivity of the nested RT-PCR. From these cases, 318 acute serum specimens or extracted RNA, previously found to be negative by the nested RT-PCR, were tested using TaqMan real-time RT-PCR (TaqMan rRT-PCR). To improve the sensitivity of nested RT-PCR, we designed a new primer based on nucleotide sequences from contemporary strains found to be positive by the TaqMan rRT-PCR. Sensitivity of the new nested PCR was calculated using a panel of 87 samples collected during 2011-2013. RESULTS AND CONCLUSION: The percentage of dengue IgM/IgG ELISA positive cases that were negative by the nested RT-PCR varied from 17% to 42% for all serotypes depending on the year. Using TaqMan rRT-PCR, dengue RNA was detected in 194 (61%) of the 318 acute sera or extracted RNA previously found to be negative by the nested RT-PCR. The newly designed DENV-1 specific primer increased the sensitivity of DENV-1 detection by the nested RT-PCR from 48% to 88%, and of all 4 serotypes from 73% to 87%. These findings demonstrate the impact of genetic diversity and signal erosion on the sensitivity of PCR-based methods.

Advances in the understanding, management, and prevention of dengue.

Dengue causes more human morbidity globally than any other vector-borne viral disease. Recent research has led to improved epidemiological methods that predict disease burden and factors involved in transmission, a better understanding of immune responses in infection, and enhanced animal models. In addition, a number of control measures, including preventative vaccines, are in clinical trials. However, significant gaps remain, including the need for better surveillance in large parts of the world, methods to predict which individuals will develop severe disease, and immunologic correlates of protection against dengue illness. During the next decade, dengue will likely expand its geographic reach and become an increasing burden on health resources in affected areas. Licensed vaccines and antiviral agents are needed in order to effectively control dengue and limit disease.