Emergence of Epidemic Dengue-1 Virus in the Southern Province of Sri Lanka

Epidemiological burden of dengue in Sri Lanka: A systematic review of literature from 2000-2020

Objectives

The objective of this systematic literature review (SLR) was to analyze changes in theepidemiological pattern of dengue in Sri Lanka from 2000 to 2020.

Methods

The review adhered to Cochrane Handbook and PRISMA guidelines, with data sourced from PubMed, Embase, Cochrane, and DARE. The search focused on English-language publications from 2000 to 2020, using keywords such as dengue epidemiology, incidence, serotype prevalence, and case fatality rates in Sri Lanka.

Results

A total of 149 publications (68 peer-reviewed and 81 grey literature sources) were included. Findings confirmed that dengue is endemic in Sri Lanka, with a marked increase in cases during major epidemics. The highest incidences were recorded in 2017 (186,101 cases) and 2019 (105,049 cases). Among the affected districts Colombo and Gampaha have the highest notification rates. The disease is reported year-round, with peaks during the monsoon seasons. From 2012 to 2019, the most affected age groups were 25-49-year-olds, followed by younger demographics. All four DENV serotypes cocirculated, with DENV-2 dominating since 2017. Case fatality rates ranged from 0.11% to 1.0%, peaking in 2009.

Conclusions

This review underscores the rising burden of dengue in Sri Lanka, highlighting the need for enhanced surveillance, prevention strategies, and potential vaccination to curb its spread.

Host-response transcriptional biomarkers accurately discriminate bacterial and viral infections of global relevance

Diagnostic limitations challenge management of clinically indistinguishable acute infectious illness globally. Gene expression classification models show great promise distinguishing causes of fever. We generated transcriptional data for a 294-participant (USA, Sri Lanka) discovery cohort with adjudicated viral or bacterial infections of diverse etiology or non-infectious disease mimics. We then derived and cross-validated gene expression classifiers including: 1) a single model to distinguish bacterial vs. viral (Global Fever-Bacterial/Viral [GF-B/V]) and 2) a two-model system to discriminate bacterial and viral in the context of noninfection (Global Fever-Bacterial/Viral/Non-infectious [GF-B/V/N]). We then translated to a multiplex RT-PCR assay and independent validation involved 101 participants (USA, Sri Lanka, Australia, Cambodia, Tanzania). The GF-B/V model discriminated bacterial from viral infection in the discovery cohort an area under the receiver operator curve (AUROC) of 0.93. Validation in an independent cohort demonstrated the GF-B/V model had an AUROC of 0.84 (95% CI 0.76-0.90) with overall accuracy of 81.6% (95% CI 72.7-88.5). Performance did not vary with age, demographics, or site. Host transcriptional response diagnostics distinguish bacterial and viral illness across global sites with diverse endemic pathogens.

Characterizing dengue transmission in rural areas: A systematic review

Dengue has historically been considered an urban disease associated with dense human populations and the built environment. Recently, studies suggest increasing dengue virus (DENV) transmission in rural populations. It is unclear whether these reports reflect recent spread into rural areas or ongoing transmission that was previously unnoticed, and what mechanisms are driving this rural transmission. We conducted a systematic review to synthesize research on dengue in rural areas and apply this knowledge to summarize aspects of rurality used in current epidemiological studies of DENV transmission given changing and mixed environments. We described how authors defined rurality and how they defined mechanisms for rural dengue transmission. We systematically searched PubMed, Web of Science, and Embase for articles evaluating dengue prevalence or cumulative incidence in rural areas. A total of 106 articles published between 1958 and 2021 met our inclusion criteria. Overall, 56% (n = 22) of the 48 estimates that compared urban and rural settings reported rural dengue incidence as being as high or higher than in urban locations. In some rural areas, the force of infection appears to be increasing over time, as measured by increasing seroprevalence in children and thus likely decreasing age of first infection, suggesting that rural dengue transmission may be a relatively recent phenomenon. Authors characterized rural locations by many different factors, including population density and size, environmental and land use characteristics, and by comparing their context to urban areas. Hypothesized mechanisms for rural dengue transmission included travel, population size, urban infrastructure, vector and environmental factors, among other mechanisms. Strengthening our understanding of the relationship between rurality and dengue will require a more nuanced definition of rurality from the perspective of DENV transmission. Future studies should focus on characterizing details of study locations based on their environmental features, exposure histories, and movement dynamics to identify characteristics that may influence dengue transmission.

Direct and indirect costs for hospitalized patients with dengue in Southern Sri Lanka

Background

The Southern Province of Sri Lanka is endemic with dengue, with frequent outbreaks and occurrence of severe disease. However, the economic burden of dengue is poorly quantified. Therefore, we conducted a cost analysis to assess the direct and indirect costs associated with hospitalized patients with dengue to households and to the public healthcare system.

Methods

From June 2017–December 2018, we prospectively enrolled children and adults with acute dengue hospitalized at the largest, public tertiary-care (1800 bed) hospital in the Southern Province, Sri Lanka. We administered a structured questionnaire to obtain information regarding direct costs spent by households on medical visits, medications, laboratory testing, and travel for seeking care for the illness. Indirect costs lost by households were estimated by identifying the days of work lost by patients and caregivers and school days lost by children. Direct hospital costs were estimated using gross costing approach and adjusted by multiplying by annual inflation rates in Sri Lankan rupees and converted to US dollars.

Results

A total of 1064 patients with laboratory-confirmed dengue were enrolled. The mean age (SD) was 35.9 years (15.6) with male predominance (66.2%). The mean durations of hospitalization for adults and paediatric patients were 3.86 (SD = 1.51) and 4 (SD = 1.32) days, respectively. The per-capita direct cost borne by the healthcare system was 233.76 USD, and was approximately 14 times greater than the per-capita direct cost borne by households (16.29 USD, SD = 14.02). The per-capita average number of loss of working days was 21.51 (SD = 41.71), with mean per-capita loss of income due to loss of work being 303.99 USD (SD = 569.77), accounting for over 70% of average monthly income. On average, 10.88 days (SD = 10.97) of school days were missed due to the dengue episode. School misses were expected to reduce future annual income of affected children by 0.44%.

Conclusions

Dengue requiring hospitalization had a substantial economic burden on the public healthcare system in Sri Lanka and the affected households. These findings emphasize the importance of strengthening dengue control activities and improved use of hospital-based resources for care to reduce the economic impact of dengue in Sri Lanka.

Outcomes among children and adults at risk of severe dengue in Sri Lanka: Opportunity for outpatient case management in countries with high disease burden

Background

Healthcare systems in dengue-endemic countries are often overburdened due to the high number of patients hospitalized according to dengue management guidelines. We systematically evaluated clinical outcomes in a large cohort of patients hospitalized with acute dengue to support triaging of patients to ambulatory versus inpatient management in the future.

Methods/Principal findings

From June 2017- December 2018, we conducted surveillance among children and adults with fever within the prior 7 days who were hospitalized at the largest tertiary-care (1,800 bed) hospital in the Southern Province, Sri Lanka. Patients who developed platelet count ≤100,000/μL (threshold for hospital admission in Sri Lanka) and who met at least two clinical criteria consistent with dengue were eligible for enrollment. We confirmed acute dengue by testing sera collected at enrollment for dengue NS1 antigen or IgM antibodies. We defined primary outcomes as per the 1997 and 2009 World Health Organization (WHO) classification criteria: dengue hemorrhagic fever (DHF; WHO 1997), dengue shock syndrome (DSS; WHO 1997), and severe dengue (WHO 2009). Overall, 1064 patients were confirmed as having acute dengue: 318 (17.4%) by NS1 rapid antigen testing and 746 (40.7%) by IgM antibody testing. Of these 1064 patients, 994 (93.4%) were adults ≥18 years and 704 (66.2%) were male. The majority (56, 80%) of children and more than half of adults (544, 54.7%) developed DHF during hospitalization, while 6 (8.6%) children and 22 (2.2%) adults developed DSS. Overall, 10 (14.3%) children and 113 (11.4%) adults developed severe dengue. A total of 2 (0.2%) patients died during hospitalization.

Conclusions

One-half of patients hospitalized with acute dengue progressed to develop DHF and a very small number developed DSS or severe dengue. Developing an algorithm for triaging patients to ambulatory versus inpatient management should be the future goal to optimize utilization of healthcare resources in dengue-endemic countries.

In countries where dengue is prevalent, hospitals are often overwhelmed due to the high numbers of patient admissions during dengue epidemics. We studied 1064 children and adults hospitalized with acute dengue in Sri Lanka to determine the prevalence of severe disease outcomes to support the development of a system which can limit hospitalizations in the future. We found that only half of patients developed severe disease outcomes during hospitalization and only a small minority of patients developed life-threatening disease. For dengue-prevalent countries, developing systems to identify patients with acute dengue who can be managed without hospital admission should be a priority.

Circulating dengue virus serotypes and vertical transmission in Aedes larvae during outbreak and inter-outbreak seasons in a high dengue risk area of Sri Lanka

Background

Spatial and temporal changes in the dengue incidence are associated with multiple factors, such as climate, immunity among a population against dengue viruses (DENV), circulating DENV serotypes and vertical transmission (VT) of DENV in an area at a given time. The level of VT in a specific location has epidemiological implications in terms of viral maintenance in vectors. Identification of the circulating DENV serotypes in both patients and Aedes mosquito larvae in an area may be useful for the early detection of outbreaks. We report here the results of a prospective descriptive study that was conducted to detect the levels of VT in Aedes mosquito larvae and circulating DENV serotypes in patients and Aedes mosquito larvae from December 2015 to March 2017 in an area of Sri Lanka at high risk for dengue.

Methods

A total of 200 patients with clinically suspected dengue who had been admitted to a tertiary care hospital during a dengue outbreak (3 study periods: December 2015–January 2016, June–August 2016, December 2016–January 2017) and in the inter-outbreak periods (February–May 2016 and September–November 2016) were investigated. Blood samples were drawn from the study participants to test for DENV. The houses of the study participants were visited within 7 days of admission to the hospital, and Aedes larvae were also collected within a radius of 400 m from the houses. The larvae were separately identified to species and then pooled according to each patient’s identification number. Patients’ sera and the Aedes larvae were tested to identify the infecting DENV serotypes using a reverse transcription PCR (RT-PCR) method. Levels of VT in Aedes mosquito larvae were also identified.

Results

All four DENV serotypes (DENV-1 to -4) were identified in the study area. In the early part of the study (December 2015–February 2016), DENV-3 was predominant and from April 2016 to March 2017, DENV-2 became the most predominant type. Four cases of DENV co-infections were noted during the study period in patients. Interestingly, all four DENV serotypes were detected in Aedes albopictus larvae, which was the prominent immature vectorial form identified throughout the study period in the area, showing 9.8% VT of DENV. With the exception of DENV-4, the other three DENV serotypes were identified in Aedes aegypti larvae with a VT of 8.1%.

Conclusion

Comparatively high rates of VT of DENV was detected in Ae. albopictus and Ae. aegypti larvae. A shift in the predominant DENV serotype with simultaneous circulation of all four DENV serotypes was identified in the study area from December 2015 to March 2017.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-05114-5.

The Host Response to Viral Infections Reveals Common and Virus-Specific Signatures in the Peripheral Blood

Viruses cause a wide spectrum of clinical disease, the majority being acute respiratory infections (ARI). In most cases, ARI symptoms are similar for different viruses although severity can be variable. The objective of this study was to understand the shared and unique elements of the host transcriptional response to different viral pathogens. We identified 162 subjects in the US and Sri Lanka with infections due to influenza, enterovirus/rhinovirus, human metapneumovirus, dengue virus, cytomegalovirus, Epstein Barr Virus, or adenovirus. Our dataset allowed us to identify common pathways at the molecular level as well as virus-specific differences in the host immune response. Conserved elements of the host response to these viral infections highlighted the importance of interferon pathway activation. However, the magnitude of the responses varied between pathogens. We also identified virus-specific responses to influenza, enterovirus/rhinovirus, and dengue infections. Influenza-specific differentially expressed genes (DEG) revealed up-regulation of pathways related to viral defense and down-regulation of pathways related to T cell and neutrophil responses. Functional analysis of entero/rhinovirus-specific DEGs revealed up-regulation of pathways for neutrophil activation, negative regulation of immune response, and p38MAPK cascade and down-regulation of virus defenses and complement activation. Functional analysis of dengue-specific up-regulated DEGs showed enrichment of pathways for DNA replication and cell division whereas down-regulated DEGs were mainly associated with erythrocyte and myeloid cell homeostasis, reactive oxygen and peroxide metabolic processes. In conclusion, our study will contribute to a better understanding of molecular mechanisms to viral infections in humans and the identification of biomarkers to distinguish different types of viral infections.

Epidemiology of dengue virus infections in Nepal, 2006-2019

BACKGROUND

Dengue is one of the newest emerging diseases in Nepal with increasing burden and geographic spread over the years. The main objective of this study was to explore the epidemiological patterns of dengue since its first outbreak (2006) to 2019 in Nepal.

METHODS

This study is a retrospective analysis that covers the last 14 years (2006-2019) of reported dengue cases from Epidemiology Diseases Control Division (EDCD), Ministry of Health and Population, Government of Nepal. Reported cases were plotted over time and maps of reported case incidence were generated (from 2016 through 2019). An ecological analysis of environmental predictors of case incidence was conducted using negative binomial regression.

RESULTS

While endemic dengue has been reported in Nepal since 2006, the case load has increased over time and in 2019 a total of 17 992 dengue cases were reported from 68 districts (from all seven provinces). Compared to the case incidence in 2016, incidence was approximately five times higher in 2018 [incidence rate ratio (IRR): 4.8; 95% confidence interval (CI) 1.5-15.3] and over 140 times higher in 2019 (IRR: 141.6; 95% CI 45.8-438.4). A one standard deviation increase in elevation was associated with a 90% decrease in reported case incidence (IRR: 0.10; 95% CI 0.01-0.20). However, the association between elevation and reported cases varied across the years. In 2018 there was a cluster of cases reported from high elevation Kaski District of Gandaki Province. Our results suggest that dengue infections are increasing in magnitude and expanding out of the lowland areas to higher elevations over time.

CONCLUSIONS

There is a high risk of dengue outbreak in the lowland Terai region, with increasing spread towards the mid-mountains and beyond as seen over the last 14 years. Urgent measures are required to increase the availability of diagnostics and resources to mitigate future dengue epidemics.

Emergence of genotype I of dengue virus serotype 3 during severe dengue epidemic in Sri Lanka, 2017

During the 2017 outbreak of severe dengue in Sri Lanka, dengue virus (DENV) serotypes 2, 3 and 4 were co-circulating. Based on our previous study on the 295 patients from the National Hospital Kandy in Sri Lanka between March 2017-January 2018, the dominant infecting serotype was DENV-2. Here, we aimed to characterize the DENV-3 strains from non-severe and severe dengue patients from our previous study population. Patients' clinical records and previous laboratory tests including dengue-specific nonstructural protein 1 antigen rapid test, IgM-capture and IgG enzyme-linked immunosorbent assays, were analyzed together with the present results of real-time reverse transcription polymerase chain reaction, and next-generation sequencing of DENV-3. Based on complete genome analysis, DENV-3 isolates belonged to two different clades of genotype I and were genetically close to the strains from Indonesia, China, Singapore, Malaysia and Australia. There were sixteen amino acid changes among DENV-3 isolates, and the greater number of changes was found in nonstructural than structural proteins. The emergence of DENV-3 genotype I was noted for the first time in Sri Lanka. Continuous monitoring of this newly emerged genotype and other DENV serotypes/genotypes are needed to determine their effects on future outbreaks and to understand the molecular epidemiology of dengue.

Whole Genome Sequencing of Dengue Virus Serotype 2 from Two Clinical Isolates and Serological Profile of Dengue in the 2015-2016 Nepal Outbreak

Dengue virus (DENV) is the cause of one of the most prevalent neglected tropical diseases, and up to half of the world's population is at risk for infection. Recent results from clinical trials have shown that DENV vaccination can induce the development of severe dengue disease and/or prolong hospitalization after natural infection in certain naive populations. Thus, it is crucial that vaccine development takes into account the history of DENV exposure in the targeted population. In Nepal, DENV infection was first documented in 2004, and despite the increasing prevalence of DENV infection, the population remains relatively naive. However, it is not known which of the four DENV serotypes circulate in Nepal or whether there is evidence of repeated exposure to DENV in the Nepali population. To address this, we studied 112 patients who presented with symptomology suspicious for DENV infection at clinics throughout Nepal during late 2015 and early 2016. Of the 112 patients examined, 39 showed serological and/or genetic evidence of primary or secondary DENV infection: 30 were positive for DENV exposure by IgM/IgG ELISA, two by real-time reverse-transcription PCR (RT-PCR), and seven by both methods. Dengue virus 1-3, but not DENV4, serotypes were detected by RT-PCR. Whole genome sequencing of two DENV2 strains isolated from patients with primary and secondary infections suggests that DENV was introduced into Nepal through India, with which it shares a porous border. Further study is needed to better define the DENV epidemic in Nepal, a country with limited scientific resources and infrastructure.

Geospatial analysis of dengue emergence in rural areas in the Southern Province of Sri Lanka

BACKGROUND

Dengue is a major cause of acute febrile illness in Sri Lanka. Dengue has historically been considered an urban disease. In 2012-2013, we documented that acute dengue was surprisingly associated with self-reported rural residence in the Southern Province of Sri Lanka.

METHODS

Patients admitted with an acute febrile illness were enrolled from June 2012-May 2013 in a cross-sectional surveillance study at the largest tertiary care hospital in the Southern Province. Acute dengue was diagnosed by serology and virology testing. Site visits were performed to collect residential geographical coordinates. Spatial variation in odds of acute dengue was modeled using a spatial generalized additive model predicted onto a grid of coordinate pairs covering the Southern Province.

RESULTS

Of 800 patients, 333 (41.6%) had laboratory-confirmed acute dengue. Dengue was spatially heterogeneous (local probability of acute dengue 0.26 to 0.42). There were higher than average odds of acute dengue in the rural northeast of the Southern Province and lower than average odds in the urbanized southwest of the Southern Province, including the city Galle.

CONCLUSIONS

Our study further affirms the emergence of dengue in rural southern Sri Lanka and highlights both the need for real-time geospatial analyses to optimize public health activities as well as the importance of strengthening dengue surveillance in non-urban areas.

Previously Derived Host Gene Expression Classifiers Identify Bacterial and Viral Etiologies of Acute Febrile Respiratory Illness in a South Asian Population

Background

Pathogen-based diagnostics for acute respiratory infection (ARI) have limited ability to detect etiology of illness. We previously showed that peripheral blood-based host gene expression classifiers accurately identify bacterial and viral ARI in cohorts of European and African descent. We determined classifier performance in a South Asian cohort.

Methods

Patients ≥15 years with fever and respiratory symptoms were enrolled in Sri Lanka. Comprehensive pathogen-based testing was performed. Peripheral blood ribonucleic acid was sequenced and previously developed signatures were applied: a pan-viral classifier (viral vs nonviral) and an ARI classifier (bacterial vs viral vs noninfectious).

Results

Ribonucleic acid sequencing was performed in 79 subjects: 58 viral infections (36 influenza, 22 dengue) and 21 bacterial infections (10 leptospirosis, 11 scrub typhus). The pan-viral classifier had an overall classification accuracy of 95%. The ARI classifier had an overall classification accuracy of 94%, with sensitivity and specificity of 91% and 95%, respectively, for bacterial infection. The sensitivity and specificity of C-reactive protein (>10 mg/L) and procalcitonin (>0.25 ng/mL) for bacterial infection were 100% and 34%, and 100% and 41%, respectively.

Conclusions

Previously derived gene expression classifiers had high predictive accuracy at distinguishing viral and bacterial infection in South Asian patients with ARI caused by typical and atypical pathogens.

Incidence and epidemiological features of dengue in Sabah, Malaysia

In South East Asia, dengue epidemics have increased in size and geographical distribution in recent years. We examined the spatiotemporal distribution and epidemiological characteristics of reported dengue cases in the predominantly rural state of Sabah, in Malaysian Borneo-an area where sylvatic and urban circulation of pathogens are known to intersect. Using a public health data set of routinely notified dengue cases in Sabah between 2010 and 2016, we described demographic and entomological risk factors, both before and after a 2014 change in the clinical case definition for the disease. Annual dengue incidence rates were spatially variable over the 7-year study period from 2010-2016 (state-wide mean annual incidence of 21 cases/100,000 people; range 5-42/100,000), but were highest in rural localities in the western districts of the state (Kuala Penyu, Nabawan, Tenom and Kota Marudu). Eastern districts exhibited lower overall dengue rates, although a high proportion of severe (haemorrhagic) dengue cases (44%) were focused in Sandakan and Tawau. Dengue incidence was highest for those aged between 10 and 29 years (24/100,000), and was slightly higher for males compared to females. Available vector surveillance data indicated that during large outbreaks in 2015 and 2016 the mosquito Aedes albopictus was more prevalent in both urban and rural households (House Index of 64%) than Ae. aegypti (15%). Demographic patterns remained unchanged both before and after the dengue case definition was changed; however, in the years following the change, reported case numbers increased substantially. Overall, these findings suggest that dengue outbreaks in Sabah are increasing in both urban and rural settings. Future studies to better understand the drivers of risk in specific age groups, genders and geographic locations, and to test the potential role of Ae. albopictus in transmission, may help target dengue prevention and control efforts.

Risk Factors Associated with Fatal Dengue Hemorrhagic Fever in Adults: A Case Control Study

Background

Dengue is endemic in most parts of the tropics with a significant mortality of 1-5%. Although individual case reports and case series have been published, large-scale case controls studies are few. The objective of this study was to find clinical and laboratory predictors of mortality in dengue.

Methods

Hospital case record based case control study was performed.

Results

Twenty fatalities with 80 controls were analyzed. Clinical parameters of postural dizziness (OR 3.2; 95% CI 1.1-8.9), bleeding (OR 31.9; 95% CI 6.08-167.34), presence of plasma leakage (OR 64.6; 95% CI 7.45-560.5), abdominal tenderness (OR 2.24; 95% CI 0.79-6.38), and signs of cardiorespiratory instability at admission increased the risk of dying from dengue. Altered consciousness was exclusively seen in 20% of cases. Laboratory parameters of elevated CRP (OR 1.652; 95% CI 1.28-2.14), AST, or ALT > 500 IU/L (OR 52.5; 95% CI 12.52-220.1) and acute kidney injury (AKI) (OR 103.5; 95% CI 13.26-807.78) during hospital stay increased the odds of dying. Need for assisted ventilation and multiorgan dysfunction (MOD) were exclusively seen in the cases. Multivariate logistic regression revealed bleeding at admission, AKI, and elevated hepatic transaminase >500 IU/L to be independent predictors of mortality.

Conclusions

This case control study revealed that mortality from dengue could be predicted using clinical parameters at admission and low cost routine laboratory investigations.

Molecular characterization and phylogenetic analysis of dengue viruses imported into Taiwan during 2011-2016

A total of 1,596 laboratory-confirmed imported dengue cases were identified in Taiwan during 2011–2016. Most of the imported cases arrived from Southeast Asia as well as the Indian subcontinent, the Pacific region, Latin America, Australia and Africa. Phylogenetic analyses of the complete envelope protein gene sequences from 784 imported dengue virus (DENV) isolates were conducted, and the results suggest that the DENV-1 genotype I and DENV-2 Cosmopolitan genotype comprise the predominant serotype/genotype of DENV strains circulating in Southeast Asia. The DENV-1 genotype III, DENV-3 genotype III and DENV-4 genotype I and II strains were found to be newly emerging in several Southeast Asian countries. Our results also showed that geographical restrictions of DENV-1 genotype I, DENV-1 genotype III and DENV-2 Cosmopolitan genotype are becoming blurred, indicating the extensive introductions and continuous expansions of DENV strains between nations in Southeast Asia. In this study, we present the geographic distribution and dynamic transmission of DENV strains circulating in Southeast Asian countries. In addition, we demonstrated local dengue epidemics caused by several imported DENV strains in Taiwan during 2011–2016.

Dengue is the most prevalent mosquito-borne viral disease in the world. The expansion of dengue viruses to different parts of the world has been accelerated by the increase in worldwide travel and trade. In this study, we present the results of a laboratory-based dengue surveillance in Taiwan during 2011–2016. A total of 1,596 laboratory-confirmed imported dengue cases were identified. The travelers were infected in 29 countries in Southeast Asia, the Indian subcontinent, the Pacific region, Latin America, Australia and Africa. Phylogenetic analyses of the envelope gene sequences of 784 imported dengue virus isolates suggest that the DENV-1 genotype I and DENV-2 Cosmopolitan genotype comprise the predominant serotype/genotype DENV strains circulating in Southeast Asia. Our results also showed that geographical restrictions of some of the DENV genotypes are becoming blurred, indicating the extensive introductions and continuous expansions of DENV strains between countries in Southeast Asia. In addition, we demonstrated dengue outbreaks in Taiwan caused by viruses imported from Asia and the Americas. The DENV envelope gene sequences from this study will contribute to a better understanding of the genetic evolution, dynamic transmission and global expansion of dengue viruses.

Profile of the 2016 dengue outbreak in Nepal

OBJECTIVE

The objective of this study was to obtain clinical, virological and demographic data detailing the 2016 dengue outbreak in Nepal.

RESULTS

Dengue disease was first reported in Nepal in 2004 and several major outbreaks have occurred since then, with a significant impact on public health. An outbreak of dengue fever occurred in Nepal during June to November 2016, with a peak number of cases reported in September. 1473 patients with laboratory confirmed DENV infections visited or were admitted to hospitals during this period. The most common clinical symptoms included fever, headache, joint pain and thrombocytopenia. Serotyping of 75 serum samples from patients having fever for less than 4 days was carried out with a dengue virus (DENV) serotype-specific RT-PCR strategy. Our results indicate that the dengue outbreak in Nepal during 2016 was caused predominantly, if not exclusively, by DENV-1, representing a shift in the prevailing serotype from DENV-2, the dominant serotype characterizing the 2013 dengue epidemic in Nepal. Hopefully, this report will assist Nepalese public health agencies in developing improved dengue-related programs including mosquito-vector control, DENV surveillance, and diagnosis and treatment of dengue fever patients, in order to reduce the impact of future dengue epidemics.

Evaluation of the WHO 2009 classification for diagnosis of acute dengue in a large cohort of adults and children in Sri Lanka during a dengue-1 epidemic

BACKGROUND

Dengue is a leading cause of fever and mimics other acute febrile illnesses (AFI). In 2009, the World Health Organization (WHO) revised criteria for clinical diagnosis of dengue.

METHODOLOGY/PRINCIPAL FINDINGS

The new WHO 2009 classification of dengue divides suspected cases into three categories: dengue without warning signs, dengue with warning signs and severe dengue. We evaluated the WHO 2009 classification vs physicians' subjective clinical diagnosis (gestalt clinical impression) in a large cohort of patients presenting to a tertiary care center in southern Sri Lanka hospitalized with acute febrile illness. We confirmed acute dengue in 388 patients (305 adults ≥ 18 years and 83 children), including 103 primary and 245 secondary cases, of 976 patients prospectively enrolled with AFI. At presentation, both adults and children with acute dengue were more likely than those with other AFI to have leukopenia and thrombocytopenia. Additionally, adults were more likely than those with other AFI to have joint pain, higher temperatures, and absence of crackles on examination whereas children with dengue were more likely than others to have sore throat, fatigue, oliguria, and elevated hematocrit and transaminases. Similarly, presence of joint pain, thrombocytopenia, and absence of cough were independently associated with secondary vs primary dengue in adults whereas no variables were different in children. The 2009 WHO dengue classification was more sensitive than physicians' clinical diagnosis for identification of acute dengue (71.5% vs 67.1%), but was less specific. However, despite the absence of on-site diagnostic confirmation of dengue, clinical diagnosis was more sensitive on discharge (75.2%). The 2009 WHO criteria classified almost 75% as having warning signs, even though only 9 (2.3%) patients had evidence of plasma leakage and 16 (4.1%) had evidence of bleeding.

CONCLUSIONS/SIGNIFICANCE

In a large cohort with AFI, we identified features predictive of dengue vs other AFI and secondary vs primary dengue in adults versus children. The 2009 WHO dengue classification criteria had high sensitivity but low specificity compared to physicians' gestaldt diagnosis. Large cohort studies will be needed to validate the diagnostic yield of clinical impression and specific features for dengue relative to the 2009 WHO classification criteria.

Novel tools for the surveillance and control of dengue: findings by the DengueTools research consortium

BACKGROUND

Dengue fever persists as a major global disease burden, and may increase as a consequence of climate change. Along with other measures, research actions to improve diagnosis, surveillance, prevention, and predictive models are highly relevant. The European Commission funded the DengueTools consortium to lead a major initiative in these areas, and this review synthesises the outputs and findings of this work conducted from 2011 to 2016. Research areas: DengueTools organised its work into three research areas, namely [1] Early warning and surveillance systems; [2] Strategies to prevent dengue in children; and [3] Predictive models for the global spread of dengue. Research area 1 focused on case-studies undertaken in Sri Lanka, including developing laboratory-based sentinel surveillance, evaluating economic impact, identifying drivers of transmission intensity, evaluating outbreak prediction capacity and developing diagnostic capacity. Research area 2 addressed preventing dengue transmission in school children, with case-studies undertaken in Thailand. Insecticide-treated school uniforms represented an intriguing potential approach, with some encouraging results, but which were overshadowed by a lack of persistence of insecticide on the uniforms with repeated washing. Research area 3 evaluated potential global spread of dengue, particularly into dengue-naïve areas such as Europe. The role of international travel, changing boundaries of vectors, developing models of vectorial capacity under different climate change scenarios and strategies for vector control in outbreaks was all evaluated.

CONCLUDING REMARKS

DengueTools was able to make significant advances in methods for understanding and controlling dengue transmission in a range of settings. These will have implications for public health agendas to counteract dengue, including vaccination programmes.

OUTLOOK

Towards the end of the DengueTools project, Zika virus emerged as an unexpected epidemic in the central and southern America. Given the similarities between the dengue and Zika viruses, with vectors in common, some of the DengueTools thinking translated readily into the Zika situation.

Analysis of Dengue Serotype 4 in Sri Lanka during the 2012-2013 Dengue Epidemic

The four serotypes of dengue virus (DENV-1, -2, -3, and -4) have had a rapidly expanding geographic range and are now endemic in over 100 tropical and subtropical countries. Sri Lanka has experienced periodic dengue outbreaks since the 1960s, but since 1989 epidemics have become progressively larger and associated with more severe disease. The dominant virus in the 2012 epidemic was DENV-1, but DENV-4 infections were also commonly observed. DENV-4 transmission was first documented in Sri Lanka when it was isolated from a traveler in 1978, but has been comparatively uncommon since dengue surveillance began in the early 1980s. To better understand the molecular epidemiology of DENV-4 infections in Sri Lanka, we conducted whole-genome sequencing on dengue patient samples from two different geographic locations. Phylogenetic analysis indicates that all sequenced DENV-4 strains belong to genotype 1 and are most closely related to DENV-4 viruses previously found in Sri Lanka and those recently found to be circulating in India and Pakistan.