Severe Dengue Fever Outbreak in Taiwan

Exploring the therapeutic potential of DV-B-120 as an inhibitor of dengue virus infection

Dengue fever, an infectious disease prevalent in subtropical and tropical regions, currently lacks effective small-molecule drugs as treatment. In this study, we used a fluorescence peptide cleavage assay to screen seven compounds to assess their inhibition of the dengue virus (DENV) NS2B-NS3 protease. DV-B-120 demonstrated superior inhibition of NS2B-NS3 protease activity and lower toxicity compared to ARDP0006. The selectivity index of DV-B-120 was higher than that of ARDP0006. In vivo assessments of the antiviral efficacy of DV-B-120 against DENV replication demonstrated delayed mortality of suckling mice treated with the compound, with 60-80% protection against life-threatening effects, compared to the outcomes of DENV-infected mice treated with saline. The lower clinical scores of DENV-infected mice treated with DV-B-120 indicated a reduction in acute-progressive illness symptoms, underscoring the potential therapeutic impact of DV-B-120. Investigations of DV-B-120's ability to restore the antiviral type I IFN response in the brain tissue of DENV-infected ICR suckling mice demonstrated its capacity to stimulate IFN and antiviral IFN-stimulated gene expression. DV-B-120 not only significantly delayed DENV-2-induced mortality and illness symptoms but also reduced viral numbers in the brain, ultimately restoring the innate antiviral response. These findings strongly suggest that DV-B-120 holds promise as a therapeutic agent against DENV infection and highlight its potential contribution in addressing the current lack of effective treatments for this infectious disease.IMPORTANCEThe prevalence of dengue virus (DENV) infection in tropical and subtropical regions is escalating due to factors like climate change and mosquito vector expansion. With over 300 million annual infections and potentially fatal outcomes, the urgent need for effective treatments is evident. While the approved Dengvaxia vaccine has variable efficacy, there are currently no antiviral drugs for DENV. This study explores seven compounds targeting the NS2B-NS3 protease, a crucial protein in DENV replication. These compounds exhibit inhibitory effects on DENV-2 NS2B-NS3, holding promise for disrupting viral replication and preventing severe manifestations. However, further research, including animal testing, is imperative to assess therapeutic efficacy and potential toxicity. Developing safe and potent treatments for DENV infection is critical in addressing the rising global health threat posed by this virus.

Modern technologies and solutions to enhance surveillance and response systems for emerging zoonotic diseases

Background

Zoonotic diseases originating in animals pose a significant threat to global public health. Recent outbreaks, such as coronavirus disease 2019 (COVID-19), have caused widespread illness, death, and socioeconomic disruptions worldwide. To cope with these diseases effectively, it is crucial to strengthen surveillance capabilities and establish rapid response systems.

Aim

The aim of this review to examine the modern technologies and solutions that have the potential to enhance zoonotic disease surveillance and outbreak responses and provide valuable insights into how cutting-edge innovations could be leveraged to prevent, detect, and control emerging zoonotic disease outbreaks. Herein, we discuss advanced tools including big data analytics, artificial intelligence, the Internet of Things, geographic information systems, remote sensing, molecular diagnostics, point-of-care testing, telemedicine, digital contact tracing, and early warning systems.

Results

These technologies enable real-time monitoring, the prediction of outbreak risks, early anomaly detection, rapid diagnosis, and targeted interventions during outbreaks. When integrated through collaborative partnerships, these strategies can significantly improve the speed and effectiveness of zoonotic disease control. However, several challenges persist, particularly in resource-limited settings, such as infrastructure limitations, costs, data integration and training requirements, and ethical implementation.

Conclusion

With strategic planning and coordinated efforts, modern technologies and solutions offer immense potential to bolster surveillance and outbreak responses, and serve as a critical resource against emerging zoonotic disease threats worldwide.

Joint influence of architectural and spatiotemporal factors on the presence of Aedes aegypti in urban environments

BACKGROUND

Urbanization has led to the proliferation of high-rise buildings, which have substantially influenced the distribution of dengue vectors, such as Aedes aegypti (L.). However, knowledge gaps exist regarding the individual and combined effects of architectural and spatiotemporal factors on dengue vector. This study investigated the interrelationship between Ae. aegypti presence, building architectural features, and spatiotemporal factors in urban environments.

RESULTS

The mosquito Ae. aegypti presence varied by location and seasons, being higher in outdoor environments than in indoor environments. Lingya (Kaohsiung City, Taiwan) had the highest mosquito numbers, particularly in basement and first floor areas. Ae. aegypti was found on multiple floors within buildings, and their presence was greater in summer and autumn. The XGBoost model revealed that height within a building, temperature, humidity, resident density, and rainfall were key factors influencing mosquito presence, whereas openness had a relatively minor impact.

CONCLUSION

To effectively address the problems caused by urbanization, the three-dimensional distribution of Ae. aegypti, including their spatial distribution across heights and areas within the urban environment, must be considered. By incorporating these multiple factors, this approach provides valuable insights for those responsible for urban planning and disease management strategies. Understanding the interplay between architectural features, environmental conditions, and the presence of Ae. aegypti is essential for developing targeted interventions and mitigating the adverse impacts of urbanization on public health. © 2023 Society of Chemical Industry.

Dengue overview: An updated systemic review

Dengue is caused by the dengue virus (DENVs) infection and clinical manifestations include dengue fever (DF), dengue hemorrhagic fever (DHF), or dengue shock syndrome (DSS). Due to a lack of antiviral drugs and effective vaccines, several therapeutic and control strategies have been proposed. A systemic literature review was conducted according to PRISMA guidelines to select proper references to give an overview of DENV infection. Results indicate that understanding the virus characteristics and epidemiology are essential to gain the basic and clinical knowledge as well as dengue disseminated pattern and status. Different factors and mechanisms are thought to be involved in the presentation of DHF and DSS, including antibody-dependent enhancement, immune dysregulation, viral virulence, host genetic susceptibility, and preexisting dengue antibodies. This study suggests that dissecting pathogenesis and risk factors as well as developing different types of therapeutic and control strategies against DENV infection are urgently needed.

Dengue Meteorological Determinants during Epidemic and Non-Epidemic Periods in Taiwan

The identification of the key factors influencing dengue occurrence is critical for a successful response to the outbreak. It was interesting to consider possible differences in meteorological factors affecting dengue incidence during epidemic and non-epidemic periods. In this study, the overall correlation between weekly dengue incidence rates and meteorological variables were conducted in southern Taiwan (Tainan and Kaohsiung cities) from 2007 to 2017. The lagged-time Poisson regression analysis based on generalized estimating equation (GEE) was also performed. This study found that the best-fitting Poisson models with the smallest QICu values to characterize the relationships between dengue fever cases and meteorological factors in Tainan (QICu = −8.49 × 10−3) and Kaohsiung (−3116.30) for epidemic periods, respectively. During dengue epidemics, the maximum temperature with 2-month lag (β = 0.8400, p < 0.001) and minimum temperature with 5-month lag (0.3832, p < 0.001). During non-epidemic periods, the minimum temperature with 3-month lag (0.1737, p < 0.001) and mean temperature with 2-month lag (2.6743, p < 0.001) had a positive effect on dengue incidence in Tainan and Kaohsiung, respectively.

The role of voltage-gated sodium channel genotypes in pyrethroid resistance in Aedes aegypti in Taiwan

Background

Aedes aegypti is the major vector of dengue that threatens public health in tropical and subtropical regions. Pyrethroid-based control strategies effectively control this vector, but the repeated usage of the same insecticides leads to resistance and hampers control efforts. Therefore, efficient and prompt monitoring of insecticide resistance in local mosquito populations is critical for dengue control.

Methodology/Principal finding

We collected Ae. aegypti in southern Taiwan in March and October 2016. We analyzed the voltage-gated sodium channel (vgsc) genotypes of parentals (G0) and G1 adults after cypermethrin insecticide bioassay. Our results showed that four VGSC mutations (S989P, V1016G, F1534C, and D1763Y) associated with resistance were commonly detected in field-collected Ae. aegypti. The frequencies of these four mutations in the local mosquito population were significantly higher in October (0.29, 0.4, 0.27 and 0.11) than in March (0.09, 0.16, 0.18 and 0.03). Specific vgsc combined genotypes composed of the one to four such mutations (SGFY/SGFY, SVCD/SVCD, SGFY/PGFD, SVCD/SGFY, PGFD/PGFD, and SVCD/PGFD) shifted towards higher frequencies in October, implying their resistance role. In addition, the cypermethrin exposure bioassay data supported the field observations. Moreover, our study observed an association between the resistance level and the proportion of resistance genotypes in the population.

Conclusions/Significance

This is the first study to demonstrate the role of four-locus vgsc genotypes in resistance evaluation in a local Ae. aegypti population in Taiwan. This alternative method using resistance-associated genotypes as an indicator of practically insecticide resistance monitoring is a useful tool for providing precise and real-time information for decision makers.

Dengue outbreaks occur annually in Taiwan, and pyrethroid insecticides are commonly used to reduce mosquito density. Insecticide resistance of mosquitoes is commonly observed in the field and threatens vector control programs. Here, we analyzed the association between the combined vgsc genotype and resistance phenotype based on field surveillance data in March and October and a cypermethrin exposure bioassay. Resistance-attributable specific vgsc genotypes were proposed. Using the combined vgsc genotype rather than each vgsc allele is recommended for better resistance prediction to provide real-time information for control program managers.

Risk Factors Associated with Passengers with Imported Dengue Fever at International Airports in Taiwan

Dengue fever (DF) is a mosquito-borne disease prevalent in the tropics (e.g., sub-Saharan Africa, Asia, and Central and South America) and a common cause of febrile illness in travelers. The high incidence of imported DF in Taiwan has led to a domestic outbreak. This study explored the risk factors associated with individuals given diagnoses of imported DF at international airports in Taiwan. The results may serve as a reference for DF prevention. In this retrospective study, data from the symptom notification system database of the Taiwan Centers for Disease Control (TCDC) were used. These data concerned travelers who returned to Taiwan from DF-endemic areas with suspected DF symptoms. The epidemiological characteristics of the cases were analyzed, and 28 variables related to DF infection were included in the multivariate logistic regression analysis. In 2018-2019, there were 8656 cases (451 positive and 8205 negative cases). The results revealed DF symptoms and a 16-30-day stay in endemic areas to be independent risk factors and the presence of three respiratory symptoms and <10 days of short-term travel to be protective factors. These results may enable the accurate assessment of symptoms in travelers with DF as well as the risk factors associated with imported DF, lowering the risk of indigenous DF outbreaks caused by imported DF.

Impact of Intrahost NS5 Nucleotide Variations on Dengue Virus Replication

Due to the nature of RNA viruses, their high mutation rates produce a population of closely related but genetically diverse viruses, termed quasispecies. To determine the role of quasispecies in DENV disease severity, 22 isolates (10 from mild cases, 12 from fatal cases) were obtained, amplified, and sequenced with Next Generation Sequencing using the Illumina MiSeq platform. Using variation calling, unique wildtype nucleotide positions were selected and analyzed for variant nucleotides between mild and fatal cases. The analysis of variant nucleotides between mild and fatal cases showed 6 positions with a significant difference of p < 0.05 with 1 position in the structural region, and 5 positions in the non-structural (NS) regions. All variations were found to have a higher percentage in fatal cases. To further investigate the genetic changes that affect the virus’s properties, reverse genetics (rg) viruses containing substitutions with the variations were generated and viral growth properties were examined. We found that the virus variant rgNS5-T7812G (G81G) had higher replication rates in both Baby hamster kidney cells (BHK-21) and Vero cells while rgNS5-C9420A (A617A) had a higher replication rate only in BHK-21 cells compared to wildtype virus. Both variants were considered temperature sensitive whereby the viral titers of the variants were relatively lower at 39°C, but was higher at 35 and 37°C. Additionally, the variants were thermally stable compared to wildtype at temperatures of 29, 37, and 39°C. In conclusion, viral quasispecies found in isolates from the 2015 DENV epidemic, resulted in variations with significant difference between mild and fatal cases. These variations, NS5-T7812G (G81G) and NS5-C9420A (A617A), affect viral properties which may play a role in the virulence of DENV.

Identification of geographic clusters for temporal heterogeneity with application to dengue surveillance

Identifying transmission of hot spots with temporal trends is important for reducing infectious disease propagation. Cluster analysis is a particularly useful tool to explore underlying stochastic processes between observations by grouping items into categories by their similarity. In a study of epidemic propagation, clustering geographic regions that have similar time series could help researchers track diffusion routes from a common source of an infectious disease. In this article, we propose a two‐stage scan statistic to classify regions into various geographic clusters by their temporal heterogeneity. The proposed scan statistic is more flexible than traditional methods in that contiguous and nonproximate regions with similar temporal patterns can be identified simultaneously. A simulation study and data analysis for a dengue fever infection are also presented for illustration.

IL-18: The Forgotten Cytokine in Dengue Immunopathogenesis

Dengue fever is an infection by the dengue virus (DENV) transmitted by vector mosquitoes. It causes many infections in tropical and subtropical countries every year, thus posing a severe disease threat. Cytokine storms, one condition where many proinflammatory cytokines are mass-produced, might lead to cellular dysfunction in tissue/organ failures and often facilitate severe dengue disease in patients. Interleukin- (IL-) 18, similar to IL-1β, is a proinflammatory cytokine produced during inflammation following inflammasome activation. Inflammatory stimuli, including microbial infections, damage signals, and cytokines, all induce the production of IL-18. High serum IL-18 is remarkably correlated with severely ill dengue patients; however, its possible roles have been less explored. Based on the clinical and basic findings, this review discusses the potential immunopathogenic role of IL-18 when it participates in DENV infection and dengue disease progression based on existing findings and related past studies.

Novel High-Throughput Multiplex qPCRs for the Detection of Canine Vector-Borne Pathogens in the Asia-Pacific

The Asia-Pacific hosts a large diversity of canine vector-borne pathogens (VBPs) with some of the most common and most pathogenic, generating significant mortality as well as a spectrum of health impacts on local dog populations. The VBPs Anaplasma platys, Babesia gibsoni, Babesia vogeli, Ehrlichia canis, Hepatozoon canis and haemotropic Mycoplasma spp. are all endemic throughout the region, with many exhibiting shifting geographical distributions that warrant urgent attention. Moreover, many of these species cause similar clinical signs when parasitising canine hosts, whilst knowledge of the exact pathogen is critical to ensure treatment is effective. This is complicated by frequent coinfection that can exacerbate pathology. Here, we describe the development, optimisation and validation of two novel quadruplex Taq-Man based real-time PCRs (qPCRs) for the specific and sensitive detection of the aforementioned VBPs. To ensure accurate evaluation of diagnostic performance, results of our qPCRs were evaluated on field samples from Thai dogs and compared with both conventional PCR (cPCR) results and next-generation sequencing (NGS) metabarcoding. Our qPCRs were found to be more sensitive at detecting canine VBP than cPCR and generated results similar to those achieved by NGS. These qPCRs will provide a valuable high-throughput diagnostic tool available to epidemiologists, researchers and clinicians for the diagnosis of key canine VBPs in the Asia-Pacific and further afield.

Clinical characteristics and risk factors for intracranial hemorrhage or infarction in patients with dengue

BACKGROUND

Intracranial hemorrhage (ICH) or infarction in dengue cases is rare but very challenging for clinicians. We report these uncommon complications of dengue patients and focused on the significant factors associated with ICH or infarction in dengue patients.

METHODS

This investigation was a retrospective study of 182 adult dengue patients who received brain computed tomography at three Taiwan hospitals during the 2014 and 2015 dengue outbreaks. This included 13 hemorrhage cases, 26 infarction cases and 143 cases without brain infarction or hemorrhage.

RESULTS

Among them, 13 (7.14%) suffered from ICH (6 had subdural hemorrhage, 3 had subarachnoid hemorrhage, 1 had subdural and subarachnoid hemorrhage, and 3 had intracerebral hemorrhage) and 26 (14.3%) had brain infarction. The overall mortality rate was 4/13 (30.8%) in the ICH group and 3/26 (11.5%) in the infarction group. The significant variables from the univariate analysis, including difference between 2014 and 2015, age, history of cerebrovascular accident, bone pain, arthralgia, dizziness, altered consciousness, and a higher Charlson comorbidity score. Multivariate analysis revealed that significant risk factors for ICH/infarction in dengue cases were the year of occurrence, 2014 vs. 2015 (p < 0.0001, OR = 25.027, 95% CI = 8.205-76.336), Charlson score >4 (p = 0.01, OR = 3.764, 95% CI = 1.364-10.386) and altered consciousness (p < 0.0001, OR = 6.3, 95% CI = 2.242-17.7). The factors physicians should notice in dengue endemic regions for brain infarction or ICH include altered consciousness and a Charlson score >4, especially in the year that a higher frequency of infarction/ICH was observed.

Mapping the cryptic spread of the 2015-2016 global Zika virus epidemic

BACKGROUND

Zika virus (ZIKV) emerged as a global epidemic in 2015-2016 from Latin America with its true geographical extent remaining unclear due to widely presumed underreporting. The identification of locations with potential and unknown spread of ZIKV is a key yet understudied component for outbreak preparedness. Here, we aim to identify locations at a high risk of cryptic ZIKV spread during 2015-2016 to further the understanding of the global ZIKV epidemiology, which is critical for the mitigation of the risk of future epidemics.

METHODS

We developed an importation simulation model to estimate the weekly number of ZIKV infections imported in each susceptible spatial unit (i.e. location that did not report any autochthonous Zika cases during 2015-2016), integrating epidemiological, demographic, and travel data as model inputs. Thereafter, a global risk model was applied to estimate the weekly ZIKV transmissibility during 2015-2016 for each location. Finally, we assessed the risk of onward ZIKV spread following importation in each susceptible spatial unit to identify locations with a high potential for cryptic ZIKV spread during 2015-2016.

RESULTS

We have found 24 susceptible spatial units that were likely to have experienced cryptic ZIKV spread during 2015-2016, of which 10 continue to have a high risk estimate within a highly conservative scenario, namely, Luanda in Angola, Banten in Indonesia, Maharashtra in India, Lagos in Nigeria, Taiwan and Guangdong in China, Dakar in Senegal, Maputo in Mozambique, Kinshasa in Congo DRC, and Pool in Congo. Notably, among the 24 susceptible spatial units identified, some have reported their first ZIKV outbreaks since 2017, thus adding to the credibility of our results (derived using 2015-2016 data only).

CONCLUSION

Our study has provided valuable insights into the potentially high-risk locations for cryptic ZIKV circulation during the 2015-2016 pandemic and has also laid a foundation for future studies that attempt to further narrow this key knowledge gap. Our modelling framework can be adapted to identify areas with likely unknown spread of other emerging vector-borne diseases, which has important implications for public health readiness especially in resource-limited settings.

Safety of temporary interruption of antiplatelet therapy in dengue fever with thrombocytopenia

Thrombocytopenia commonly occurs in dengue and may be complicated by bleeding. Dengue can occur in adults who may be on long term antiplatelet therapy for ischemic heart disease or stroke. In these cases, clinicians may temporarily discontinue antiplatelet therapy to minimize the risk of bleeding in the absence of clear guidelines. We conducted a retrospective cohort study of laboratory-confirmed adult dengue patients on antiplatelet therapy and evaluated participants whose antiplatelet therapy was continued versus discontinued. Primary outcome was a composite outcome of major adverse cardiac and cerebrovascular events (MACCE), and all-cause mortality in-hospital and for 1-year post discharge. Secondary outcomes were platelet and blood transfusion, and occurrence of dengue haemorrhagic fever (DHF), dengue shock syndrome, dengue with warning signs and severe dengue according to World Health Organization criteria. Discontinuation of antiplatelet therapy did not result in higher composite outcome (p=0.192). Continuation of antiplatelet therapy did not result in more platelet or blood transfusion (p=0.489 and p=0.567 respectively), DHF (p=0.923). Our results suggest that discontinuation or continuation of antiplatelet therapy based on clinical judgement in dengue with thrombocytopenia, is largely safe but further studies are needed.

Real-time dengue forecast for outbreak alerts in Southern Taiwan

Dengue fever is a viral disease transmitted by mosquitoes. In recent decades, dengue fever has spread throughout the world. In 2014 and 2015, southern Taiwan experienced its most serious dengue outbreak in recent years. Some statistical models have been established in the past, however, these models may not be suitable for predicting huge outbreaks in 2014 and 2015. The control of dengue fever has become the primary task of local health agencies. This study attempts to predict the occurrence of dengue fever in order to achieve the purpose of timely warning. We applied a newly developed autoregressive model (AR model) to assess the association between daily weather variability and daily dengue case number in 2014 and 2015 in Kaohsiung, the largest city in southern Taiwan. This model also contained additional lagged weather predictors, and developed 5-day-ahead and 15-day-ahead predictive models. Our results indicate that numbers of dengue cases in Kaohsiung are associated with humidity and the biting rate (BR). Our model is simple, intuitive and easy to use. The developed model can be embedded in a "real-time" schedule, and the data (at present) can be updated daily or weekly based on the needs of public health workers. In this study, a simple model using only meteorological factors performed well. The proposed real-time forecast model can help health agencies take public health actions to mitigate the influences of the epidemic.

Meteorological conditions are the most frequently mentioned factors in the study of dengue fever. Some of the main factors other than the purely meteorological about which the public-health authorities might have data, such as numbers of cases or other current measurements of dengue outbreaks in neighboring cities, had been used in some of the past dengue studies. In this study, we developed models for predicting dengue case number based on past dengue case data and meteorological data. The goal of the models is to provide early warning of the occurrence of dengue fever to assist public health agencies in preparing an epidemic response plan.

Climate change and dengue risk in central region of Thailand

Dengue poses a huge public health threat. It places physical and financial burden on individuals affected, family, and national health systems. This descriptive study aimed for two specific objectives; to investigate the weather effects on dengue incidence and to estimate level of risk in the central region of Thailand. It utilized a 10-year population level dengue morbidity data and meteorological data from 2007 to 2016. Kriging method was used to interpolate a weighted risk factor upon a 5-point risk estimate was developed for estimating area risk on a 5-point scale. The findings showed that 2 out of 16 provinces (12.5%) are strong to very strong risk areas for dengue, including Bangkok and Nonthaburi provinces. The study revealed that the impact of La Niña and El Niño on increased dengue incidence and risk level in Bangkok. We recommend further studies to establish intersections of dengue disease and social determinants of health.

Using UPLC-MS/MS to Evaluate the Dissemination of Pyriproxyfen by Aedes Mosquitoes to Combat Cryptic Larval Habitats after Source Reduction in Kaohsiung in Southern Taiwan

The policy regarding mosquito control strategies in Taiwan is based on integrated vector management (IVM). The major approach is source reduction via collaboration by both residents and governments. However, small and cryptic habitats of dengue vectors are hard to find and eliminate in urban communities. Therefore, this study evaluated a complementary approach that targeted cryptic habitats by utilizing mosquitoes themselves as vehicles to transfer an insect growth regulator, pyriproxyfen (PPF), to their breeding sites; the amount of PPF in breeding water was determined with ultra-performance liquid chromatography coupled with tandem mass spectrometry (UPLC–MS/MS). A bioassay conducted by introducing ten late-instar larvae into PPF solution was performed to assess emergence inhibition (EI). PPF was found at 0.56 ± 0.04 ng in 25 mL of water by dissemination via ten Aedes aegypti mosquitoes exposed to 0.01% PPF, leading to 100% EI. After the community-level source reduction, a field trial in Kaohsiung in Southern Taiwan showed that 30.8–31.5% of cryptic ovitraps reached EI ≥ 50% one month after spraying 0.01% PPF in microhabitats favored by mosquitoes. IVM in parallel with residual spraying of PPF on resting surfaces of mosquitoes could serve as a simple and complementary approach to reduce cryptic larval sources in urban communities in Southern Taiwan.

Dengue hemorrhagic fever - A systemic literature review of current perspectives on pathogenesis, prevention and control

BACKGROUND

Dengue is an arboviral disease caused by dengue virus. Symptomatic dengue infection causes a wide range of clinical manifestations, from mild dengue fever (DF) to potentially fatal disease, such as dengue hemorrhagic fever (DHF) or dengue shock syndrome (DSS). We conducted a literature review to analyze the risks of DHF and current perspectives for DHF prevention and control.

METHODS

According to the PRISMA guidelines, the references were selected from PubMed, Web of Science and Google Scholar database using search strings containing a combination of terms that included dengue hemorrhagic fever, pathogenesis, prevention and control. Quality of references were evaluated by independent reviewers.

RESULTS

DHF was first reported in the Philippines in 1953 and further transmitted to the countries in the region of South-East Asia and Western Pacific. Plasma leakages is the main pathophysiological hallmark that distinguishes DHF from DF. Severe plasma leakage can result in hypovolemic shock. Various factors are thought to impact disease presentation and severity. Virus virulence, preexisting dengue antibodies, immune dysregulation, lipid change and host genetic susceptibility are factors reported to be correlated with the development of DHF. However, the exact reasons and mechanisms that triggers DHF remains controversial. Currently, no specific drugs and licensed vaccines are available to treat dengue disease in any of its clinical presentations.

CONCLUSION

This study concludes that antibody-dependent enhancement, cytokine dysregulation and variation of lipid profiles are correlated with DHF occurrence. Prompt diagnosis, appropriate treatment, active and continuous surveillance of cases and vectors are the essential determinants for dengue prevention and control.

The effects of seasonal climate variability on dengue annual incidence in Hong Kong: A modelling study

In recent years, dengue has been rapidly spreading and growing in the tropics and subtropics. Located in southern China, Hong Kong’s subtropical monsoon climate may favour dengue vector populations and increase the chance of disease transmissions during the rainy summer season. An increase in local dengue incidence has been observed in Hong Kong ever since the first case in 2002, with an outbreak reaching historically high case numbers in 2018. However, the effects of seasonal climate variability on recent outbreaks are unknown. As the local cases were found to be spatially clustered, we developed a Poisson generalized linear mixed model using pre-summer monthly total rainfall and mean temperature to predict annual dengue incidence (the majority of local cases occur during or after the summer months), over the period 2002-2018 in three pre-defined areas of Hong Kong. Using leave-one-out cross-validation, 5 out of 6 observations of area-specific outbreaks during the major outbreak years 2002 and 2018 were able to be predicted. 42 out of a total of 51 observations (82.4%) were within the 95% confidence interval of the annual incidence predicted by our model. Our study found that the rainfall before and during the East Asian monsoon (pre-summer) rainy season is negatively correlated with the annual incidence in Hong Kong while the temperature is positively correlated. Hence, as mosquito control measures in Hong Kong are intensified mainly when heavy rainfalls occur during or close to summer, our study suggests that a lower-than-average intensity of pre-summer rainfall should also be taken into account as an indicator of increased dengue risk.

Effects of Chinese and Western Medicine on Patients with Dengue Fever

Dengue fever is an important epidemic disease with a high prevalence in tropical and subtropical countries. We aimed to investigate the effects of a treatment integrating traditional Chinese (TCM) and Western medicines on dengue inpatients with warning signs (i.e., group B) according to the World Health Organization dengue classification in this retrospective cohort study of medical records. Inpatients who were treated with conventional Western therapies in the absence or presence of TCM were assigned to the control and treatment groups, respectively. Data were compared using an analysis of variance, general linear analysis, and chi-square test. The most common clinical symptoms and signs of dengue fever were fever and muscle ache. The treatment group patients were significantly more likely to present general weakness and poor appetite than the control group patients. Patients in the treatment group were more likely to experience stomachache than those in the control group. Moreover, comparisons of the changes in hemoglobin and alanine aminotransferase levels over time revealed significant differences between the patient groups. Zhu Ye Shi Gao Tang, Gui Pi Tang, Paeonia suffruticosa, and Clerodendrum cyrtophyllum were the most commonly administered TCM formula and single herbs in this study. Patients in the treatment group experienced a resolution of symptoms, signs, and laboratory data and were discharged smoothly, without deterioration to death or critical care. Our findings suggest that the integration of TCM and Western medicine may yield an appropriate treatment for dengue fever.

Latent Infectious Capacities of Dengue Fever: Mathematical Modeling and Eco-Friendly Prevention Strategy

The main aim of this article is to propose a method for exploring the latent values about the capacities of spreading dengue for each potential site. First, a mathematical model connecting the observable public data and the capacities of spreading dengue is provided based on the split feasibility problem (SFP). Then, a proper iterative scheme for the SFP is presented to approach the values of infectious capacities (ICs) of potential sites—the capacities of spreading. The performance of our proposed method is demonstrated using public data from Kaohsiung City for 2014 and 2015. The results presented in this paper show that our proposed method is reliable and the sites with a high capacity of spreading are only a small portion of thousands of all potential sites and could be an alternative strategy for preventing the outbreak of dengue fever whilst also avoiding the damage of ecosystems caused by chemical insecticides.

Severe dengue and liver involvement: an overview and review of the literature

Introduction: Two billion population are at risk of dengue fever and by 2080, over six billion population will be at risk. Hepatitis is common in dengue and the liver is invariably involved in severe cases. We conducted a literature review using the PubMed database on articles covering a broad range of issues related to dengue and hepatitis.Areas covered: This article overviews available literature on changes in the definition of severe dengue, pathogenesis of liver involvement in dengue, clinical manifestations, and predictors of mortality in severe dengue with liver involvement, impact of viral hepatitis co-infections and hepatotoxic drugs, and hemophagocytic lymphohistiocytosis.Expert commentary: Hepatitis is commonly seen in dengue however the degree of elevation of transaminases did not correlate well with severity of illness in observational studies, except in the elderly. The underlying pathogenesis of liver injury is still being elucidated and further studies are required to fully understand the cellular pathways. Acute or chronic viral hepatitis does not appear to affect dengue outcomes. Commonly used medications such as paracetamol and statins may influence dengue outcomes.

The Impact of Dengue on Economic Growth: The Case of Southern Taiwan

Dengue has long been a public health problem in tropical and subtropical countries. In 2015, a dengue outbreak occurred in Taiwan, where 43,784 cases were reported. This study aims to assess the impact of dengue on Southern Taiwan’s economic growth according to the economic growth model-based regression approach recommended by the World Health Organization (WHO). Herein, annual data from Southern Taiwan on the number of dengue cases, income growth, and demographics from 2010–2015 were analyzed. The percentage of reduction of the average income per capita in 2015 due to the dengue outbreak was estimated. Dengue was determined to have a negative linear economic impact on Southern Taiwan’s economic growth. In particular, a reduction of 0.26% in the average income per capita was estimated in Southern Taiwan due to the 2015 outbreak. If the model is applied alongside other dengue outbreak forecast models, then the forecast for economic reduction due to a future dengue outbreak may also be estimated. Prevention and recovery policies may subsequently be decided upon based on not only the number of dengue cases but also the degree of economic burden resulting from an outbreak.

An epidemiological survey of the current status of Zika and the immune interaction between dengue and Zika infection in Southern Taiwan

OBJECTIVES

This study was performed to examine the current status of Zika and the effects of pre-existing dengue immunity on Zika virus (ZIKV) infection in Southern Taiwan.

METHODS

A phylogenetic tree was used to analyze the phylogeny of detected ZIKVs. Paired sera from dengue patients were collected for the determination of dengue and Zika infection. Plaque reduction neutralization tests (PRNT) and quantitative reverse transcription PCR (qRT-PCR) were used to determine the titers of neutralizing antibodies and viruses, respectively. An antibody-dependent enhancement (ADE) assay was used to evaluate the effect of anti-dengue antibodies on ZIKV infection.

RESULTS

Epidemiological data indicated the continuous importation of ZIKV infection from neighboring Zika epidemic countries into Taiwan. A total of 78 dengue patients were enrolled and 21 paired serum samples were obtained. PRNT₉₀ results for the 21 samples identified eight cases of primary dengue infection and 13 cases of secondary dengue infection; two samples were positive for ZIKV (MR766). Results from the ADE assay indicated that convalescent sera from primary and secondary dengue infection patients displayed significant ADE of the ZIKV infection when compared to healthy controls (p < 0.05).

CONCLUSIONS

This study suggests that pre-existing dengue immunity facilitates ZIKV infection and that the continuous importation of ZIKV infection may pose a threat to indigenous Zika emergence in Southern Taiwan.

Clinical and epidemiological characteristics of imported dengue fever among inbound passengers: Infrared thermometer-based active surveillance at an international airport

BACKGROUND

Dengue fever is endemic in tropical and subtropical areas, especially Southeast Asia. International air travel facilitates the spread of dengue across and within borders. To date, no predictive factors have been established for assessing risk of dengue among febrile travelers.

METHODS

Since 2006, Taiwan has operated a program of infrared thermometer-based non-contact active surveillance at Taoyuan International Airport (TPE). All inbound passengers from dengue-endemic countries who are febrile (tympanic temperature ≥38°C) undergo routine laboratory testing for dengue. We analyzed clinical and epidemiological characteristics of all tested passengers entering Taiwan via TPE in 2011 to identify the predictive factors of dengue infection.

RESULTS

In 2011, of the 3,719 febrile passengers from dengue-endemic countries, 74 (2.0%) had laboratory-confirmed dengue infection. Multivariable logistic regression analysis revealed that those who were aged ≥60 years (adjusted odds ratio [aOR], 8.7; 95% confidence interval [CI], 2.6-29.6) and had self-reported fever (aOR, 2.5; 95% CI, 1.5-4.1), skin rashes (aOR, 11.0; 95% CI, 3.4-35.1), or a tympanic temperature ≥39°C (aOR, 2.9; 95% CI, 1.7-4.9) were significantly more likely to have dengue (all p values < 0.05). Compared with travelers who stayed in dengue-endemic countries for ≤7 days, those who traveled 8-14, 15-21, 22-28, and ≥29 days were also more likely to be infected (aORs of 10.2, 14.9, 39.0 and 12.0, respectively).

CONCLUSION

These clinical and epidemiological features can facilitate timely recognition and diagnosis of imported dengue in febrile inbound passengers and therefore help prevent domestic transmission of dengue virus.

Exit and Entry Screening Practices for Infectious Diseases among Travelers at Points of Entry: Looking for Evidence on Public Health Impact

A scoping search and a systematic literature review were conducted to give an insight on entry and exit screening referring to travelers at points of entry, by analyzing published evidence on practices, guidelines, and experiences in the past 15 years worldwide. Grey literature, PubMed. and Scopus were searched using specific terms. Most of the available data identified through the systematic literature review concerned entry screening measures at airports. Little evidence is available about entry and exit screening measure implementation and effectiveness at ports and ground crossings. Exit screening was part of the World Health Organisation's (WHO) temporary recommendations for implementation in certain points of entry, for specific time periods. Exit screening measures for Ebola Virus Disease (EVD) in the three most affected West African countries did not identify any cases and showed zero sensitivity and very low specificity. The percentages of confirmed cases identified out of the total numbers of travelers that passed through entry screening measures in various countries worldwide for Influenza Pandemic (H1N1) and EVD in West Africa were zero or extremely low. Entry screening measures for Severe Acute Respiratory Syndrome (SARS) did not detect any confirmed SARS cases in Australia, Canada, and Singapore. Despite the ineffectiveness of entry and exit screening measures, authors reported several important concomitant positive effects that their impact is difficult to assess, including discouraging travel of ill persons, raising awareness, and educating the traveling public and maintaining operation of flights from/to the affected areas. Exit screening measures in affected areas are important and should be applied jointly with other measures including information strategies, epidemiological investigation, contact tracing, vaccination, and quarantine to achieve a comprehensive outbreak management response. Based on review results, an algorithm about decision-making for entry/exit screening was developed.

Is asthma a protective factor for dengue fever? In vitro experiment and nationwide population-based cohort analysis

BACKGROUND

Dengue fever (DF) is the most rapidly spreading mosquito-borne viral disease. Practical vaccines or specific therapeutics are still expected. Environmental factors and genetic factors affect the susceptibility of Dengue virus (DV) infection. Asthma is a common allergic disease, with house dust mites (HDMs) being the most important allergens. Asthmatic patients are susceptible to several microorganism infections.

METHODS

A nationwide population-based cohort analysis was designed to assess whether to determine whether asthma can be a risk factor for DF.

RESULTS

Unexpectedly, our data from a nationwide population-based cohort revealed asthmatic patients are at a decreased risk of DF. Compared to patients without asthma, the hazard ratio (HR) for DF in patients with asthma was 0.166 (95% CI: 0.118-0.233) after adjustment for possible confounding factors. In the age stratification, the adjusted HR for DF in young adult patients with asthma was 0.063. Dendritic cell-specific intercellular adhesion molecule 3-grabbing non-integrin (DC-SIGN) of dendritic cells (DCs) is an important entry for DV. Through another in vitro experiment, we found that HDM can diminish surface expression of DC-SIGN in monocyte-derived DCs and further decrease the cellular entry of DV.

CONCLUSIONS

Decreased DC-SIGN expression in DCs of allergic asthmatic patient may be one of many factors for them to be protected against DF. This could implicate the potential for DC-SIGN modulation as a candidate target for designing therapeutic strategies for DF.

A clinical and epidemiological survey of the largest dengue outbreak in Southern Taiwan in 2015

OBJECTIVES

This study examined the epidemiological, clinical, and immunological characteristics of the 2015 dengue outbreak in Taiwan.

METHODS

Clinical data were collected from dengue fever (DF) and dengue hemorrhagic fever (DHF) patients. A phylogenetic tree was used to analyze the source of the outbreak strain. Paired plasma samples from DF/DHF patients were used for antibody-dependent enhancement (ADE) assay and cytokine multiplex biometric immunoassay to validate the immunological mechanism.

RESULTS

This outbreak mainly occurred in two of the southern cities of Taiwan: Tainan (n=22 777; 52%) and Kaohsiung (n=19 784; 45%). A high DHF death rate was noted (34.6%). The case (DHF) and control (DF) study indicated that older age (>60 years), type II diabetes, and hypertension were risk factors correlated with the development of DHF (p< 0.0001). The phylogenetic tree results suggested that the outbreak-associated strain was dengue virus serotype 2 and cosmopolitan genotype, forming a stable cluster with the isolates from Thailand and Indonesia (bootstrap value of 99%). Cytokine analyses demonstrated that levels of interleukin (IL)-6, IL-4, IL-13, IL-1β, interferon gamma (IFN-γ), and granulocyte-macrophage colony-stimulating factor (GM-CSF) were significantly higher in DHF patients compared to DF patients (p< 0.001). The ADE assay showed that diluted plasma containing preexisting dengue antibodies from DHF patients significantly enhanced dengue infection (p< 0.05).

CONCLUSION

The results suggest that older age, type II diabetes, hypertension, immunological cytokine dysregulation, and preexisting dengue antibodies inducing ADE infection are correlated with dengue severity. This study also indicates that the largest dengue outbreak in Taiwan might have been a result of imported DF from dengue epidemic regions.

Cultural Sensitivity and Global Pharmacy Engagement in Asia: China, Japan, South Korea, and Taiwan

Interest in global engagement among schools and colleges of pharmacy in the United States and Asian countries is growing. To develop fruitful relationships and engage in mutually enriching experiences, the cultural aspects of these countries need to be understood and respected. The aim of this paper is to facilitate culturally sensitive interactions between practitioners, faculty members, and students in the United States and those in Asian countries when they engage in health care practice and/or education. This paper introduces general information about China (including Macau and Hong Kong), Japan, South Korea, and Taiwan. Unique characteristics of the health care system and pharmacy education are described for each country. Stereotypes and misconceptions are discussed. Recommendations are included for initiating interactions and developing learning programs and scholarly collaborations while promoting culturally sensitive engagement. These recommendations are provided for US scholars, health care professionals, and students traveling to these countries as well as for those hosting visitors from these countries in the United States.

A Gut Commensal Bacterium Promotes Mosquito Permissiveness to Arboviruses

Mosquitoes are hematophagous vectors that can acquire human viruses in their intestinal tract. Here, we define a mosquito gut commensal bacterium that promotes permissiveness to arboviruses. Antibiotic depletion of gut bacteria impaired arboviral infection of a lab-adapted Aedes aegypti mosquito strain. Reconstitution of individual cultivable gut bacteria in antibiotic-treated mosquitoes identified Serratia marcescens as a commensal bacterium critical for efficient arboviral acquisition. S. marcescens facilitates arboviral infection through a secreted protein named SmEnhancin, which digests membrane-bound mucins on the mosquito gut epithelia, thereby enhancing viral dissemination. Field Aedes mosquitoes positive for S. marcescens were more permissive to dengue virus infection than those free of S. marcescens. Oral introduction of S. marcescens into field mosquitoes that lack this bacterium rendered these mosquitoes highly susceptible to arboviruses. This study defines a commensal-driven mechanism that contributes to vector competence, and extends our understanding of multipartite interactions among hosts, the gut microbiome, and viruses.

Increased Adult Aedes aegypti and Culex quinquefasciatus (Diptera: Culicidae) Abundance in a Dengue Transmission Hotspot, Compared to a Coldspot, within Kaohsiung City, Taiwan

The assumption that vector abundance differences might drive spatial and temporal heterogeneities in vector-borne disease transmission is common, though data supporting it is scarce. Here, we present data from two common mosquito species Aedes aegypti (Linnaeus) and Culex quinquefasciatus Say, biweekly sampled as adults, from March 2016 through December 2017, with BG-sentinel traps in two neighboring districts of Kaohsiung City (KC), Taiwan. One district has historically been a dengue transmission hotspot (Sanmin), and the other a coldspot (Nanzih). We collected a total 41,027 mosquitoes, and we found that average mosquito abundance (mean ± S.D.) was higher in Sanmin (Ae. aegypti: 9.03 ± 1.46; Cx. quinquefasciatus: 142.57 ± 14.38) than Nanzih (Ae. aegypti: 6.21 ± 0.47; Cx. quinquefasciatus: 63.37 ± 8.71) during the study period. In both districts, Ae. aegypti and Cx. quinquefasciatus population dynamics were sensitive to changes in temperature, the most platykurtic environmental variable at KC during the study period, a pattern predicted by Schmalhausen’s law, which states that organisms are more sensitive to small changes in environmental variables whose average value is more uncertain than its extremes. Our results also suggest that differences in Ae. aegypti abundance might be responsible for spatial differences in dengue transmission at KC. Our comparative approach, where we also observed a significant increment in the abundance of Cx. quinquefasciatus in the dengue transmission hotspot, suggests this area might be more likely to experience outbreaks of other vector borne diseases and should become a primary focus for vector surveillance and control.

Global dengue death before and after the new World Health Organization 2009 case classification: A systematic review and meta-regression analysis

BACKGROUND

Since the introduction of 2009 WHO dengue case classification, no literature was found regarding its effect on dengue death. This study was to evaluate the effect of 2009 WHO dengue case classification towards dengue case fatality rate.

METHODS

Various databases were used to search relevant articles since 1995. Studies included were cohort and cross-sectional studies, all patients with dengue infection and must report the number of death or case fatality rate. The Joanna Briggs Institute appraisal checklist was used to evaluate the risk of bias of the full-texts. The studies were grouped according to the classification adopted: WHO 1997 and WHO 2009. Meta-regression was employed using a logistic transformation (log-odds) of the case fatality rate. The result of the meta-regression was the adjusted case fatality rate and odds ratio on the explanatory variables.

RESULTS

A total of 77 studies were included in the meta-regression analysis. The case fatality rate for all studies combined was 1.14% with 95% confidence interval (CI) of 0.82-1.58%. The combined (unadjusted) case fatality rate for 69 studies which adopted WHO 1997 dengue case classification was 1.09% with 95% CI of 0.77-1.55%; and for eight studies with WHO 2009 was 1.62% with 95% CI of 0.64-4.02%. The unadjusted and adjusted odds ratio of case fatality using WHO 2009 dengue case classification was 1.49 (95% CI: 0.52, 4.24) and 0.83 (95% CI: 0.26, 2.63) respectively, compared to WHO 1997 dengue case classification. There was an apparent increase in trend of case fatality rate from the year 1992-2016. Neither was statistically significant.

CONCLUSIONS

The WHO 2009 dengue case classification might have no effect towards the case fatality rate although the adjusted results indicated a lower case fatality rate. Future studies are required for an update in the meta-regression analysis to confirm the findings.

Epidemiological Characteristics and Space-Time Analysis of the 2015 Dengue Outbreak in the Metropolitan Region of Tainan City, Taiwan

The metropolitan region of Tainan City in southern Taiwan experienced a dengue outbreak in 2015. This manuscript describes basic epidemiological features of this outbreak and uses spatial and temporal analysis tools to understand the spread of dengue during the outbreak. The analysis found that, independently of gender, dengue incidence rate increased with age, and proportionally affected more males below the age of 40 years but females above the age of 40 years. A spatial scan statistic was applied to detect clusters of disease transmission. The scan statistic found that dengue spread in a north-south diffusion direction, which is across the North, West-Central and South districts of Tainan City. Spatial regression models were used to quantify factors associated with transmission. This analysis indicated that neighborhoods with high proportions of residential area (or low wetland cover) were associated with dengue transmission. However, these association patterns were non-linear. The findings presented here can help Taiwanese public health agencies to understand the fundamental epidemiological characteristics and diffusion patterns of the 2015 dengue outbreak in Tainan City. This type of information is fundamental for policy making to prevent future uncontrolled dengue outbreaks, given that results from this study suggest that control interventions should be emphasized in the North and West-Central districts of Tainan city, in areas with a moderate percentage of residential land cover.

Ascertaining the impact of public rapid transit system on spread of dengue in urban settings

Urbanization is an important factor contributing to the global spread of dengue in recent decades, especially in tropical regions. However, the impact of public transportation system on local spread of dengue in urban settings remains poorly understood, due to the difficulty in collecting relevant locality, transportation and disease incidence data with sufficient detail, and in suitably quantifying the combined effect of proximity and passenger flow. We quantify proximity and passenger traffic data relating to 2014-2015 dengue outbreaks in Kaohsiung, Taiwan by introducing a "Risk Associated with Metro Passengers Presence" (RAMPP), which considers the passenger traffic of stations located within a fixed radius, giving more weight to the busier and/or closer stations. In order to analyze the contagion risk associated with nearby presence of one or more Kaohsiung Rapid Transit (KRT) stations, we cluster the Li's (the fourth level administrative subdivision in Taiwan) of Kaohsiung based on their RAMPP value using the K-means algorithm. We then perform analysis of variance on distinct clusterings and detect significant differences for both years. The subsequent post hoc tests (Dunn) show that yearly incidence rate observed in the areas with highest RAMPP values is always significantly greater than that recorded with smaller RAMPP values. RAMPP takes into account of population mobility in urban settings via the use of passenger traffic information of urban transportation system, that captures the simple but important idea that large amount of passenger flow in and out of a station can dramatically increase the contagion risk of dengue in the neighborhood. Our study provides a new perspective in identifying high-risk areas for transmissions and thus enhances our understanding of how public rapid transit system contributes to disease spread in densely populated urban areas, which could be useful in the design of more effective and timely intervention and control measures for future outbreaks.

Increasing airline travel may facilitate co-circulation of multiple dengue virus serotypes in Asia

The incidence of dengue has grown dramatically in recent decades worldwide, especially in Southeast Asia and the Americas with substantial transmission in 2014-2015. Yet the mechanisms underlying the spatio-temporal circulation of dengue virus (DENV) serotypes at large geographical scales remain elusive. Here we investigate the co-circulation in Asia of DENV serotypes 1-3 from 1956 to 2015, using a statistical framework that jointly estimates migration history and quantifies potential predictors of viral spatial diffusion, including socio-economic, air transportation and maritime mobility data. We find that the spread of DENV-1, -2 and -3 lineages in Asia is significantly associated with air traffic. Our analyses suggest the network centrality of air traffic hubs such as Thailand and India contribute to seeding dengue epidemics, whilst China, Cambodia, Indonesia, and Singapore may establish viral diffusion links with multiple countries in Asia. Phylogeographic reconstructions help to explain how growing air transportation networks could influence the dynamics of DENV circulation.

Differences in Mortality and Clinical Manifestations of Dengue Hemorrhagic Fever in Taiwan in Different Years: A Comparison for Cases in 2014 and 2015 Epidemics

People in southern Taiwan experienced two major dengue outbreaks in 2014 and 2015. The mortality and clinical features were very different between these 2 years. Dengue virus serotype 1 (DENV-1) caused epidemic outbreak in 2014 and DENV-2 was predominant in 2015. The characteristics of dengue hemorrhagic fever (DHF) cases in the 2 years was analyzed. We conducted a retrospective chart review to analyze the clinical and laboratory features of 206 adult patients with DHF in southern Taiwan in 2014 and 2015. The mortality rate of DHF cases in 2015 was higher than that of cases in 2014 (38.7% versus 12.4%, P < 0.0001). Compared with cases in 2014, DHF cases in 2015 had more complications, such as gastrointestinal bleeding (78.5% versus 61.9%, P = 0.01), severe hepatitis (30.1% versus 8%, P < 0.0001), and myocarditis (14% versus 0.9%, P < 0.0001). Among the mortality cases, diabetes, chronic renal failure, proton-pump inhibitors using, platelet transfusion, and Charlson comorbidity index score (Charlson score) were also higher in 2015. Multivariate analysis for the mortality cases revealed that the risk factors were Charlson score ≥ 5 (P = 0.02, odds ratio [OR] = 4.07, 95% confidence interval [CI] = 1.244-13.307), severe hepatitis (P < 0.0001, OR = 11.97, 95% CI = 3.831-37.396), and acute renal failure (P < 0.0001, OR = 98.76, 95% CI = 10.847-899.22). DHF cases in 2015 had higher mortality and more complications, such as gastrointestinal bleeding, severe hepatitis, and myocarditis, than in 2014 in southern Taiwan. In the 2-year DHF case series, Charlson score ≥ 5, severe hepatitis, and acute renal failure were independent significant variables for mortality.

Ascertaining the impact of catastrophic events on dengue outbreak: The 2014 gas explosions in Kaohsiung, Taiwan

Infectious disease outbreaks often occur in the aftermath of catastrophic events, either natural or man-made. While natural disasters such as typhoons/hurricanes, flooding and earthquakes have been known to increase the risk of infectious disease outbreak, the impact of anthropogenic disasters is less well-understood. Kaohsiung City is located in southern Taiwan, where most dengue outbreaks had occurred in the past two decades. It is also the center of petrochemical industry in Taiwan with pipelines running underneath city streets. Multiple underground gas explosions occurred in Kaohsiung in the evening of July 31, 2014 due to chemical leaks in the pipelines. The explosions caused 32 deaths, including five firefighters and two volunteer firefighters, and injured 321 persons. Historically, dengue outbreaks in southern Taiwan occurred mostly in small numbers of around 2000 cases or less, except in 2002 with over 5000 cases. However, in the months after the gas explosions, the city reported 14528 lab-confirmed dengue cases from August to December. To investigate the possible impact, if any, of the gas explosions on this record-breaking dengue outbreak, a simple mathematical model, the Richards model, is utilized to study the temporal patterns of the spread of dengue in the districts of Kaohsiung in the proximity of the explosion sites and to pinpoint the waves of infections that had occurred in each district in the aftermath of the gas explosions. The reproduction number of each wave in each district is also computed. In the aftermath of the gas explosions, early waves occurred 4–5 days (which coincides with the minimum of human intrinsic incubation period for dengue) later in districts with multiple waves. The gas explosions likely impacted the timing of the waves, but their impact on the magnitude of the 2014 outbreak remains unclear. The modeling suggests the need for public health surveillance and preparedness in the aftermath of future disasters.

Prophylactic platelet transfusion plus supportive care versus supportive care alone in adults with dengue and thrombocytopenia: a multicentre, open-label, randomised, superiority trial

BACKGROUND

Dengue is the commonest vector-borne infection worldwide. It is often associated with thrombocytopenia, and prophylactic platelet transfusion is widely used despite the dearth of robust evidence. We aimed to assess the efficacy and safety of prophylactic platelet transfusion in the prevention of bleeding in adults with dengue and thrombocytopenia.

METHODS

We did an open-label, randomised, superiority trial in five hospitals in Singapore and Malaysia. We recruited patients aged at least 21 years who had laboratory-confirmed dengue (confirmed or probable) and thrombocytopenia (≤20 000 platelets per μL), without persistent mild bleeding or any severe bleeding. Patients were assigned (1:1), with randomly permuted block sizes of four or six and stratified by centre, to receive prophylactic platelet transfusion in addition to supportive care (transfusion group) or supportive care alone (control group). In the transfusion group, 4 units of pooled platelets were given each day when platelet count was 20 000 per μL or lower; supportive care consisted of bed rest, fluid therapy, and fever and pain medications. The primary endpoint was clinical bleeding (excluding petechiae) by study day 7 or hospital discharge (whichever was earlier), analysed by intention to treat. Safety outcomes were analysed according to the actual treatment received. This study was registered with ClinicalTrials.gov, number NCT01030211, and is completed.

FINDINGS

Between April 29, 2010, and Dec 9, 2014, we randomly assigned 372 patients to the transfusion group (n=188) or the control group (n=184). The intention-to-treat analysis included 187 patients in the transfusion group (one patient was withdrawn immediately) and 182 in the control group (one was withdrawn immediately and one did not have confirmed or probable dengue). Clinical bleeding by day 7 or hospital discharge occurred in 40 (21%) patients in the transfusion group and 48 (26%) patients in the control group (risk difference -4·98% [95% CI -15·08 to 5·34]; relative risk 0·81 [95% CI 0·56 to 1·17]; p=0·16). 13 adverse events occurred in the transfusion group and two occurred in the control group (5·81% [-4·42 to 16·01]; 6·26 [1·43 to 27·34]; p=0·0064). Adverse events that were possibly, probably, or definitely related to transfusion included three cases of urticaria, one maculopapular rash, one pruritus, and one chest pain, as well as one case each of anaphylaxis, transfusion-related acute lung injury, and fluid overload that resulted in serious adverse events. No death was reported.

INTERPRETATION

In adult patients with dengue and thrombocytopenia, prophylactic platelet transfusion was not superior to supportive care in preventing bleeding, and might be associated with adverse events.

FUNDING

National Medical Research Council, Singapore.

Temporal patterns of dengue epidemics: The case of recent outbreaks in Kaohsiung

OBJECTIVE

To investigate whether major dengue outbreaks in the last two decades in Kaohsiung follow a precise temporal pattern.

METHODS

Government daily lab-confirmed dengue case data from three major dengue outbreaks occurring during the last two decades in Kaohsiung in 2002, 2014 and 2015, is utilized to compute the corresponding weekly cumulative percentage of total case numbers. We divide each of the three time series data into two periods to examine the corresponding weekly cumulative percentages of case numbers for each period. Pearson's correlation coefficient was calculated to compare quantitatively the similarity between the temporal patterns of these three years.

RESULTS

Three cutoff points produce the most interesting comparisons and the most different outcomes. Pearson's correlation coefficient indicates quantitative discrepancies in the similarity between temporal patterns of the three years when using different cutoff points.

CONCLUSIONS

Temporal patterns in 2002 and 2014 are comparatively more similar in early stage. The 2015 outbreak started late in the year, but ended more like the outbreak in 2014, both with record-breaking number of cases. The retrospective analysis shows that the temporal dynamics of dengue outbreaks in Kaohsiung can strongly vary from one year to another, making it difficult to identify any common predictor.

Significance of major international seaports in the distribution of murine typhus in Taiwan

Background

International seaports are hotspots for disease invasion and pathogens can persist in seaports even after ports are abandoned. Transmitted by fleas infected by Rickettsia typhi, murine typhus, a largely neglected and easily misdiagnosed disease, is known to occur primarily in large seaports. However, the significance of seaports in the occurrence of murine typhus has never been validated quantitatively.

Methodology/Principal findings

We studied the spatial distribution of murine typhus, a notifiable disease, in Taiwan. We investigated whether risk of infection was correlated with distance to international seaports and a collection of environmental and socioeconomic factors, using a Bayesian negative binomial conditionally autoregressive model, followed with geographically weighted regression. Seaports that are currently in use and those that operated in the 19^th century for trade with China, but were later abandoned due to siltation were analyzed. A total of 476 human cases of murine typhus were reported during 2000–2014 in the main island of Taiwan, with spatial clustering in districts in southwest and central-west Taiwan. A higher incidence rate (case/population) was associated with a smaller distance to currently in-use international seaports and lower rainfall and temperature, but was uncorrelated with distance to abandoned ports. Geographically weighted regression revealed a geographic heterogeneity in the importance of distance to in-use seaports near the four international seaports of Taiwan.

Conclusions/Significance

Our study suggests that murine typhus is associated with international seaports, especially for those with large trading volume. Thus, one of the costs of global trade in Taiwan might be elevated risks of murine typhus. Globalization has accelerated the spread of infectious diseases, but the burden of disease varies geographically, with regions surrounding major international seaports warranting particular surveillance.

Globalization has hastened the spread of infectious diseases, with seaports as hotspots for disease invasion. Transmitted by fleas infected with the rickettsia Rickettsia typhi, murine typhus occurs worldwide, but its significance as a common causative agent of illness in tropical regions remains largely neglected. Although it is recognized that murine typhus is prevalent primarily in large seaports, the significance of seaports in the occurrence of murine typhus has never been validated quantitatively. We thus investigated whether distribution of murine typhus in Taiwan was associated with international seaports. Notably, abandoned international seaports (abandoned in the 19^th century due to siltation) were also studied to see whether the causative agent of murine typhus might still circulate around the ports even after being abandoned. We found that infection risk of murine typhus was negatively associated with distance to operating seaports but was uncorrelated with nearness to abandoned seaports. In addition, the importance of distance to operating seaports for risk of murine typhus infection varied spatially. Our study highlights elevated disease risk as a cost of international trade and suggests particular surveillance in regions surrounding major international seaports.

Online platform for applying space-time scan statistics for prospectively detecting emerging hot spots of dengue fever

Background

Cases of dengue fever have increased in areas of Southeast Asia in recent years. Taiwan hit a record-high 42,856 cases in 2015, with the majority in southern Tainan and Kaohsiung Cities. Leveraging spatial statistics and geo-visualization techniques, we aim to design an online analytical tool for local public health workers to prospectively identify ongoing hot spots of dengue fever weekly at the village level.

Methods

A total of 57,516 confirmed cases of dengue fever in 2014 and 2015 were obtained from the Taiwan Centers for Disease Control (TCDC). Incorporating demographic information as covariates with cumulative cases (365 days) in a discrete Poisson model, we iteratively applied space–time scan statistics by SaTScan software to detect the currently active cluster of dengue fever (reported as relative risk) in each village of Tainan and Kaohsiung every week. A village with a relative risk >1 and p value <0.05 was identified as a dengue-epidemic area. Assuming an ongoing transmission might continuously spread for two consecutive weeks, we estimated the sensitivity and specificity for detecting outbreaks by comparing the scan-based classification (dengue-epidemic vs. dengue-free village) with the true cumulative case numbers from the TCDC’s surveillance statistics.

Results

Among the 1648 villages in Tainan and Kaohsiung, the overall sensitivity for detecting outbreaks increases as case numbers grow in a total of 92 weekly simulations. The specificity for detecting outbreaks behaves inversely, compared to the sensitivity. On average, the mean sensitivity and specificity of 2-week hot spot detection were 0.615 and 0.891 respectively (p value <0.001) for the covariate adjustment model, as the maximum spatial and temporal windows were specified as 50% of the total population at risk and 28 days. Dengue-epidemic villages were visualized and explored in an interactive map.

Conclusions

We designed an online analytical tool for front-line public health workers to prospectively detect ongoing dengue fever transmission on a weekly basis at the village level by using the routine surveillance data.

Public Health Responses to and Challenges for the Control of Dengue Transmission in High-Income Countries: Four Case Studies

Dengue has a negative impact in low- and lower middle-income countries, but also affects upper middle- and high-income countries. Despite the efforts at controlling this disease, it is unclear why dengue remains an issue in affluent countries. A better understanding of dengue epidemiology and its burden, and those of chikungunya virus and Zika virus which share vectors with dengue, is required to prevent the emergence of these diseases in high-income countries in the future. The purpose of this review was to assess the relative burden of dengue in four high-income countries and to appraise the similarities and differences in dengue transmission. We searched PubMed, ISI Web of Science, and Google Scholar using specific keywords for articles published up to 05 May 2016. We found that outbreaks rarely occur where only Aedes albopictus is present. The main similarities between countries uncovered by our review are the proximity to dengue-endemic countries, the presence of a competent mosquito vector, a largely nonimmune population, and a lack of citizens' engagement in control of mosquito breeding. We identified important epidemiological and environmental issues including the increase of local transmission despite control efforts, population growth, difficulty locating larval sites, and increased human mobility from neighboring endemic countries. Budget cuts in health and lack of practical vaccines contribute to an increased risk. To be successful, dengue-control programs for high-income countries must consider the epidemiology of dengue in other countries and use this information to minimize virus importation, improve the control of the cryptic larval habitat, and engage the community in reducing vector breeding. Finally, the presence of a communicable disease center is critical for managing and reducing future disease risks.

Serum neutrophil gelatinase-associated lipocalin and resistin are associated with dengue infection in adults

BACKGROUND

Dengue is a major health problem in tropical areas, including Taiwan. Dengue virus infection affects various types of cells and results in elevation of serum inflammatory molecules. Because these molecules may be associated with dengue virus infection, the aim of this study was to identify novel molecules in febrile patients with dengue infection. In addition, we determined whether these molecules were correlated with the count of leukocytes and platelets.

METHODS

Febrile adults (Age >18 years old) who presented to the emergency department and were confirmed dengue virus infection were enrolled in this study. Serum from dengue patients and healthy controls was collected and serum level of sepsis-associated inflammatory molecules was measured by Luminex assay.

RESULTS

Elevated level of macrophage migration inhibitory factor, soluble vascular cell adhesion molecule-1, sFasL, resistin and interferon-γ were detected in patients' serum. Higher levels of neutrophil gelatinase-associated lipocalin (NGAL) and resistin were detected in dengue patients with normal leukocyte count and all dengue patients, respectively. Furthermore, the serum level of NGAL, but not resistin, was correlated with cell count in dengue patients.

CONCLUSION

Our results revealed that resistin and NGAL are novel dengue-associated molecules. These results may help elucidate the regulatory mechanisms of anti-dengue immune responses.

The outcomes of patients with severe dengue admitted to intensive care units

Outcomes of adult patients with dengue infections requiring intensive care unit (ICU) admissions remain unclear. We assessed the clinical manifestations and prognostic factors of patients critically ill with severe dengue.This retrospective study was done in a tertiary referral hospital with 96 adult ICU beds. All of the patients with laboratory-confirmed severe dengue infections and admitted to the ICU were enrolled between July 31 and November 31, 2015, during the large outbreak period. The medical records of all the recruited patients were reviewed for the following information: age, gender, clinical manifestations, disease severity scores, underlying conditions, laboratory examinations, and outcomes. The primary endpoint was to find the predictors of ICU mortality.During the study period, 4787 patients with dengue infections required ICU admission. One hundred forty-three (2.99%) were critically ill (mean age: 69.7 years). Hypertension (n = 90, 62.9%) and diabetes mellitus (n = 70, 49.0%) were the 2 most common underlying diseases. Eighty critically ill patients (55.9%) had cobacterial infections, and 33 had cobacteremia. The hematologic system failed most often, followed by thoracic and cardiovascular systems. Fever was the most common presentation (n = 112; 78.3%), followed by anorexia (n = 47; 32.9%) and abdominal pain (n = 46; 32.2%). Overall, 33 patients died (mortality rate: 23.1%). Multivariate analysis showed that ICU mortality was significantly associated with lower Glasgow Coma Scale (GCS) scores, lower platelet counts before ICU discharge, and more organ failures.The number of severe dengue patients who require ICU admission remains high. The mortality rate was associated with lower GCS scores, lower platelet counts, and more organ failures. In addition, more than half of the critically ill dengue patients had comorbid bacterial infections.

Applications of a Rapid and Sensitive Dengue DUO Rapid Immunochromatographic Test Kit as a Diagnostic Strategy during a Dengue Type 2 Epidemic in an Urban City

Dengue infection is a major health problem in tropical and subtropical countries. A prospective observational study in a university-affiliated hospital was conducted between August 2015 and September 2015. Patients who visited the emergency department (ED) with a presentation of any symptoms of dengue were eligible for the dengue non-structural protein 1 (NS1), IgM/IgG rapid immunochromatographic tests and real-time polymerase chain reaction (RT-PCR) to evaluate the performance of the rapid tests. Considering the RT-PCR as the gold standard for the dengue diagnosis, the ideal primary results of sensitivity (80–100%), specificity (60–84%), positive predicted value(75%-95%), and negative predicted value (70–100%) suggested that the NS1-based test with or without a combination of IgM and IgG tests have good diagnostic performances in detecting dengue infections, even in the afebrile or elderly populations.

Characteristics and Risk Factors for Fatality in Patients with Dengue Hemorrhagic Fever, Taiwan, 2014

An unprecedented dengue outbreak involving more than 15,000 infections, including 136 dengue hemorrhagic fever (DHF) cases and 20 fatalities, occurred in Taiwan in 2014. The median age of the DHF cases was 71 years (range: 4-92 years) and most of them (N = 100, 73.5%) had comorbidities, of which the majority were hypertension (56%) and diabetes mellitus (DM; 27%). Only approximately half of the DHF cases (59/136) were classified as severe dengue, based on the 2009 WHO-revised dengue classification. The fatality rate for this DHF outbreak was 14.7%. DM (odds ratio [OR] = 3.60, 95% confidence interval [CI] = 1.22-10.63) and presentation with severe plasma leakage (OR = 6.42, 95% CI = 1.76-23.63) were independent risk factors for fatality.

Serum Galectin-9 and Galectin-3-Binding Protein in Acute Dengue Virus Infection

Dengue fever is a serious threat for public health and induces various inflammatory cytokines and mediators, including galectins and glycoproteins. Diverse immune responses and immunological pathways are induced in different phases of dengue fever progression. However, the status of serum galectins and glycoproteins is not fully determined. The aim of this study was to investigate the serum concentration and potential interaction of soluble galectin-1, galectin-3, galectin-9, galectin-3 binding protein (galectin-3BP), glycoprotein 130 (gp130), and E-, L-, and P-selectin in patients with dengue fever in acute febrile phase. In this study, 317 febrile patients (187 dengue patients, 150 non-dengue patients that included 48 patients with bacterial infection and 102 patients with other febrile illness) who presented to the emergency department and 20 healthy controls were enrolled. Our results showed the levels of galectin-9 and galectin-3BP were significantly higher in dengue patients than those in healthy controls. Lower serum levels of galectin-1, galectin-3, and E-, L-, and P-selectin in dengue patients were detected compared to bacteria-infected patients, but not to healthy controls. In addition, strong correlation between galectin-9 and galectin-3BP was observed in dengue patients. In summary, our study suggested galectin-9 and galectin-3BP might be critical inflammatory mediators in acute dengue virus infection.