Seasonality, annual trends, and characteristics of dengue among ill returned travelers, 1997-2006

Discrepancies in dengue burden estimates: a comparative analysis of reported cases and global burden of disease study, 2010-2019

BACKGROUND

Dengue is a significant mosquito-borne disease. Several studies have utilized estimates from the Global Burden of Disease (GBD) study to assess the global, regional or national burden of dengue over time. However, our recent investigation suggests that GBD's estimates for dengue cases in Taiwan are unrealistically high. The current study extends the scope to compare reported dengue cases with GBD estimates across 30 high-burden countries and territories, aiming to assess the accuracy and interpretability of the GBD's dengue estimates.

METHODS

Data for this study were sourced from the GBD 2019 study and various national and international databases documenting reported dengue cases. The analysis targeted the top 30 countries and territories with the highest 10-year average of reported cases from 2010 to 2019. Discrepancies were quantified by computing absolute differences and ratios between the 10-year average of reported cases and GBD estimates. Coefficients of variation (CV) and estimated annual percentage changes (EAPCs) were calculated to assess variations and trends in the two data sources.

RESULTS

Significant discrepancies were noted between reported data and GBD estimates in the number of dengue cases, incidence rates, and EAPCs. GBD estimates were substantially higher than reported cases for many entities, with the most notable differences found in China (570.0-fold), India (303.0-fold), Bangladesh (115.4-fold), Taiwan (85.5-fold) and Indonesia (23.2-fold). Furthermore, the GBD's estimates did not accurately reflect the extensive yearly fluctuations in dengue outbreaks, particularly in non-endemic regions such as Taiwan, China and Argentina, as evidenced by high CVs.

CONCLUSIONS

This study reveals substantial discrepancies between GBD estimates and reported dengue cases, underscoring the imperative for comprehensive analysis in areas with pronounced disparities. The failure of GBD estimates to represent the considerable annual fluctuations in dengue outbreaks highlights the critical need for improvement in disease burden estimation methodologies for dengue.

Occupational exposure to malaria, leishmaniasis and arbovirus vectors in endemic regions: A systematic review

Vector-borne diseases, including dengue, leishmaniasis and malaria, may be more common among individuals whose occupations or behaviours bring them into frequent contact with these disease vectors outside of their homes. A systematic review was conducted to ascertain at-risk occupations and situations that put individuals at increased risk of exposure to these disease vectors in endemic regions and identify the most suitable interventions for each exposure. The review was conducted in accordance with PRISMA guidelines on articles published between 1945 and October 2021, searched in 16 online databases. The primary outcome was incidence or prevalence of dengue, leishmaniasis or malaria. The review excluded ecological and qualitative studies, abstracts only, letters, commentaries, reviews, and studies of laboratory-acquired infections. Studies were appraised, data extracted, and a descriptive analysis conducted. Bite interventions for each risk group were assessed. A total of 1170 articles were screened and 99 included. Malaria, leishmaniasis and dengue were presented in 47, 41 and 24 articles, respectively; some articles presented multiple conditions. The most represented populations were soldiers, 38% (43 of 112 studies); refugees and travellers, 15% (17) each; migrant workers, 12.5% (14); miners, 9% (10); farmers, 5% (6); rubber tappers and missionaries, 1.8% (2) each; and forest workers, 0.9% (1). Risk of exposure was categorised into round-the-clock or specific times of day/night dependent on occupation. Exposure to these vectors presents a critical and understudied concern for outdoor workers and mobile populations. When devising interventions to provide round-the-clock vector bite protection, two populations are considered. First, mobile populations, characterized by their high mobility, may find potential benefits in insecticide-treated clothing, though more research and optimization are essential. Treated clothing offers personal vector protection and holds promise for economically disadvantaged individuals, especially when enabling them to self-treat their clothing to repel vectors. Secondly, semi-permanent and permanent settlement populations can receive a combination of interventions that offer both personal and community protection, including spatial repellents, suitable for extended stays. Existing research is heavily biased towards tourism and the military, diverting attention and resources from vulnerable populations where these interventions are most required like refugee populations as well as those residing in sub-Saharan Africa.

The epidemiology of imported and locally acquired dengue in Australia, 2012-2022

BACKGROUND

Dengue is the most important arboviral disease globally and poses ongoing challenges for control including in non-endemic countries with competent mosquito vectors at risk of local transmission through imported cases. We examined recent epidemiological trends in imported and locally acquired dengue in Australia, where the Wolbachia mosquito population replacement method was implemented throughout dengue-prone areas of northern Queensland between 2011 and 2019.

METHODS

We analysed dengue cases reported to the Australian National Notifiable Disease Surveillance System between January 2012 and December 2022, and Australian traveller movement data.

RESULTS

Between 2012 and 2022, 13 343 dengue cases were reported in Australia (median 1466 annual cases); 12 568 cases (94.2%) were imported, 584 (4.4%) were locally acquired and 191 (1.4%) had no origin recorded. Locally acquired cases decreased from a peak in 2013 (n = 236) to zero in 2021-22. Annual incidence of imported dengue ranged from 8.29/100 000 (n = 917 cases) to 22.10/100 000 (n = 2203) annual traveller movements between 2012 and 2019, decreased in 2020 (6.74/100 000 traveller movements; n = 191) and 2021 (3.32/100 000 traveller movements; n = 10) during COVID-19-related border closures, then rose to 34.79/100 000 traveller movements (n = 504) in 2022. Imported cases were primarily acquired in Southeast Asia (n = 9323; 74%), Southern and Central Asia (n = 1555; 12%) and Oceania (n = 1341; 11%). Indonesia (n = 5778; 46%) and Thailand (n = 1483; 12%) were top acquisition countries. DENV-2 (n = 2147; 42%) and DENV-1 (n = 1526; 30%) were predominant serotypes.

CONCLUSION

Our analysis highlights Australia's successful control of locally acquired dengue with Wolbachia. Imported dengue trends reflect both Australian travel destinations and patterns and local epidemiology in endemic countries.

Analysis of dengue fever disease in West Africa

Dengue fever disease (DFD) which is caused by four antigenically distinct dengue viruses (DENV) presents a global health threat, with tropical and subtropical regions at a greater risk. The paucity of epidemiological data on dengue in West African subregion endangers efforts geared toward disease control and prevention. A systematic search of DFD prevalence, incidence, and DENV-infected Aedes in West Africa was conducted in PubMed, Scopus, African Index Medicus, and Google Scholar in line with the Preferred Reporting Items for Systematic reviews and Meta-analyses (PRISMA) guidelines. A total of 58 human prevalence studies involving 35,748 people from 8 countries were identified. Two incidence and six DENV-infected studies were also reviewed. Nigeria and Burkina Faso contributed the majority of the prevalence studies which spanned between 1968 and 2018, with a considerable variation in coverage among the countries reviewed in this study. An average prevalence of 20.97% was observed across both general prevalence and acute DENV infection study categories, ranging between 0.02% and 93%. The majority of these studies were conducted in acute febrile patients with a prevalence range of 0.02-93% while 19% (n = 11) of all studies were general population-based studies and reported a prevalence range of 17.2-75.8%. DENV-infected Aedes aegypti were reported in four out of the five countries with published reports; with DENV-2 found circulating in Cape Verde, Senegal, and Burkina Faso while DENV-3 and DENV-4 were also reported in Senegal and Cape Verde, respectively. High prevalence of DFD in human populations and the occurrence of DENV-infected A. aegypti have been reported in West Africa, even though weaknesses in study design were identified. Epidemiological data from most countries and population in the subregion were scarce or non-existent. This study highlights the epidemic risk of DFD in West Africa, and the need for research and surveillance to be prioritized to fill the data gap required to enact effective control measures.

Global prevalence of asymptomatic dengue infections - a systematic review and meta-analysis

OBJECTIVES

The burden of asymptomatic dengue infections is understudied. Therefore, we systematically reviewed the literature to estimate the global prevalence of asymptomatic dengue infections.

METHODS

We searched cross-sectional studies reporting the prevalence of asymptomatic dengue infections from PubMed, Scopus, and Embase. Prevalence of asymptomatic dengue infections was pooled and reported as proportions with a 95% confidence interval (CI). This systematic review protocol was a priori registered in The International Prospective Register of Systematic Reviews (Reg: No. CRD42020218446).

RESULTS

We included 41 studies with 131,953 cases in our analysis. The overall pooled prevalence of asymptomatic dengue infections was 59.26% (95% CI: 43.76-74.75, I2 = 99.93%), with 65.52% (95% CI: 38.73-92.32, I2 = 99.95%) during outbreaks and 30.78% (95% CI: 21.39-40.16, I2 = 98.78%) during non-outbreak periods. The pooled prevalence among the acutely infected individuals was 54.52% (95% CI: 17.73-46.76, I2 = 99.91%), whereas, among primary and secondary asymptomatic dengue infections, it was 65.36% (95% CI: 45.76-84.96, I2 = 98.82) and 48.99% (95% CI: 27.85-70.13, I2 = 99.08%) respectively.

CONCLUSION

The majority of dengue cases are asymptomatic and may play a significant role in disease transmission. Public health strategies aimed at dengue outbreak response and mitigation of disease burden should include early detection of asymptomatic cases.

Arboviral vaccines for use in pregnant travelers

Pregnant women traveling abroad can be exposed to a variety of arboviruses, primarily spread by mosquitoes or ticks. Some arboviral infections can be of particular concern for pregnant women or their fetuses. Vaccination is one preventive measure that can reduce the risk for infection. Several arboviral vaccines have been licensed for many years and can be used to prevent infection in travelers, namely Japanese encephalitis, yellow fever, and tick-borne encephalitis vaccines. Recommendations on use of these vaccines in pregnancy vary. Other arboviral vaccines have been licensed but are not indicated for use in pregnant travelers (e.g., dengue vaccines) or are in development (e.g., chikungunya, Zika vaccines). This review describes arboviral vaccines for travelers, focusing on women who are pregnant and those planning travel during pregnancy.

Clinical Characteristics and Outcomes Among Travelers With Severe Dengue : A GeoSentinel Analysis

BACKGROUND

Dengue virus is a flavivirus transmitted by Aedes mosquitoes and is an important cause of illness worldwide. Data on the severity of travel-associated dengue illness are limited.

OBJECTIVE

To describe the epidemiology, clinical characteristics, and outcomes among international travelers with severe dengue or dengue with warning signs as defined by the 2009 World Health Organization classification (that is, complicated dengue).

DESIGN

Retrospective chart review and analysis of travelers with complicated dengue reported to GeoSentinel from January 2007 through July 2022.

SETTING

20 of 71 international GeoSentinel sites.

PATIENTS

Returning travelers with complicated dengue.

MEASUREMENTS

Routinely collected surveillance data plus chart review with abstraction of clinical information using predefined grading criteria to characterize the manifestations of complicated dengue.

RESULTS

Of 5958 patients with dengue, 95 (2%) had complicated dengue. Eighty-six (91%) patients had a supplemental questionnaire completed. Eighty-five of 86 (99%) patients had warning signs, and 27 (31%) were classified as severe. Median age was 34 years (range, 8 to 91 years); 48 (56%) were female. Patients acquired dengue most frequently in the Caribbean (n = 27 [31%]) and Southeast Asia (n = 21 [24%]). Frequent reasons for travel were tourism (46%) and visiting friends and relatives (32%). Twenty-one of 84 (25%) patients had comorbidities. Seventy-eight (91%) patients were hospitalized. One patient died of nondengue-related illnesses. Common laboratory findings and signs were thrombocytopenia (78%), elevated aminotransferase (62%), bleeding (52%), and plasma leakage (20%). Among severe cases, ophthalmologic pathology (n = 3), severe liver disease (n = 3), myocarditis (n = 2), and neurologic symptoms (n = 2) were reported. Of 44 patients with serologic data, 32 confirmed cases were classified as primary dengue (IgM+/IgG-) and 12 as secondary (IgM-/IgG+) dengue.

LIMITATIONS

Data for some variables could not be retrieved by chart review for some patients. The generalizability of our observations may be limited.

CONCLUSION

Complicated dengue is relatively rare in travelers. Clinicians should monitor patients with dengue closely for warning signs that may indicate progression to severe disease. Risk factors for developing complications of dengue in travelers need further prospective study.

PRIMARY FUNDING SOURCE

Centers for Disease Control and Prevention, International Society of Travel Medicine, Public Health Agency of Canada, and GeoSentinel Foundation.

Dengue outbreak amongst travellers returning from Cuba-GeoSentinel surveillance network, January-September 2022

Increasing numbers of travellers returning from Cuba with dengue virus infection were reported to the GeoSentinel Network from June to September 2022, reflecting an ongoing local outbreak. This report demonstrates the importance of travellers as sentinels of arboviral outbreaks and highlights the need for early identification of travel-related dengue.

Correlation of Dengue and Meteorological Factors in Bangladesh: A Public Health Concern

Dengue virus (DENV) is an enveloped, single-stranded RNA virus, a member of the Flaviviridae family (which causes Dengue fever), and an arthropod-transmitted human viral infection. Bangladesh is well known for having some of Asia's most vulnerable Dengue outbreaks, with climate change, its location, and it's dense population serving as the main contributors. For speculation about DENV outbreak characteristics, it is crucial to determine how meteorological factors correlate with the number of cases. This study used five time series models to observe the trend and forecast Dengue cases. Current data-based research has also applied four statistical models to test the relationship between Dengue-positive cases and meteorological parameters. Datasets were used from NASA for meteorological parameters, and daily DENV cases were obtained from the Directorate General of Health Service (DGHS) open-access websites. During the study period, the mean of DENV cases was 882.26 ± 3993.18, ranging between a minimum of 0 to a maximum of 52,636 daily confirmed cases. The Spearman's rank correlation coefficient between climatic variables and Dengue incidence indicated that no substantial relationship exists between daily Dengue cases and wind speed, temperature, and surface pressure (Spearman's rho; r = -0.007, p > 0.05; r = 0.085, p > 0.05; and r = -0.086, p > 0.05, respectively). Still, a significant relationship exists between daily Dengue cases and dew point, relative humidity, and rainfall (r = 0.158, p < 0.05; r = 0.175, p < 0.05; and r = 0.138, p < 0.05, respectively). Using the ARIMAX and GA models, the relationship for Dengue cases with wind speed is -666.50 [95% CI: -1711.86 to 378.86] and -953.05 [-2403.46 to 497.36], respectively. A similar negative relation between Dengue cases and wind speed was also determined in the GLM model (IRR = 0.98). Dew point and surface pressure also represented a negative correlation in both ARIMAX and GA models, respectively, but the GLM model showed a positive association. Additionally, temperature and relative humidity showed a positive correlation with Dengue cases (105.71 and 57.39, respectively, in the ARIMAX, 633.86, and 200.03 in the GA model). In contrast, both temperature and relative humidity showed negative relation with Dengue cases in the GLM model. In the Poisson regression model, windspeed has a substantial significant negative connection with Dengue cases in all seasons. Temperature and rainfall are significantly and positively associated with Dengue cases in all seasons. The association between meteorological factors and recent outbreak data is the first study where we are aware of the use of maximum time series models in Bangladesh. Taking comprehensive measures against DENV outbreaks in the future can be possible through these findings, which can help fellow researchers and policymakers.

Cross-platform mobile app development for disseminating public health information to travelers in Thailand: development and usability

Background

The risk of disease is a key factor that travelers have identified when planning to travel abroad, as many people are concerned about getting sick. Mobile devices can be an effective means for travelers to access information regarding disease prevalence in their planned destinations, potentially reducing the risk of exposure.

Methods

We developed a mobile app, ThaiEpidemics, using cross-platform technology to provide information about disease prevalence and status for travelers to Thailand. We aimed to assess the app’s usability in terms of engagement, search logs, and effectiveness among target users. The app was developed using the principle of mobile application development life cycle, for both iOS and Android. As its data source, the app used weekly data from national disease-surveillance reports. We conduced our study among visitors to the Travel Clinic in the Hospital for Tropical Diseases, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand. The participants were informed that the app would collect usage and search logs related to their queries. After the second log-in, the app prompted participants to complete an e-survey regarding their opinions and preferences related to their awareness of disease prevalence and status.

Results

We based our prototype of ThaiEpidemics on a conceptualized framework for visualizing the distribution of 14 major diseases of concern to tourists in Southeast Asia. The app provided users with functions and features to search for and visualize disease prevalence and status in Thailand. The participants could access information for their current location and elsewhere in the country. In all, 83 people installed the app, and 52 responded to the e-survey. Regardless of age, education, and continent of origin, almost all e-survey respondents believed the app had raised their awareness of disease prevalence and status when travelling. Most participants searched for information for all 14 diseases; some searched for information specifically about dengue and malaria.

Conclusions

ThaiEpidemics is evidently potentially useful for travelers. Should the app be adopted for use by travelers to Thailand, it could have an impact on wider knowledge distribution, which might result in decreased exposure, increased prophylaxis, and therefore a potential decreased burden on the healthcare system. For app developers who are developing/implementing this kind of app, it is important to address standardization of the data source and users’ concerns about the confidentiality and safety of their mobile devices.

Dengue: A Growing Problem With New Interventions

Dengue is the disease caused by 1 of 4 distinct, but closely related dengue viruses (DENV-1-4) that are transmitted by Aedes spp. mosquito vectors. It is the most common arboviral disease worldwide, with the greatest burden in tropical and sub-tropical regions. In the absence of effective prevention and control measures, dengue is projected to increase in both disease burden and geographic range. Given its increasing importance as an etiology of fever in the returning traveler or the possibility of local transmission in regions in the United States with competent vectors, as well as the risk for large outbreaks in endemic US territories and associated states, clinicians should understand its clinical presentation and be familiar with appropriate testing, triage, and management of patients with dengue. Control and prevention efforts reached a milestone in June 2021 when the Advisory Committee on Immunization Practices (ACIP) recommended Dengvaxia for routine use in children aged 9 to 16 years living in endemic areas with laboratory confirmation of previous dengue virus infection. Dengvaxia is the first vaccine against dengue to be recommended for use in the United States and one of the first to require laboratory testing of potential recipients to be eligible for vaccination. In this review, we outline dengue pathogenesis, epidemiology, and key clinical features for front-line clinicians evaluating patients presenting with dengue. We also provide a summary of Dengvaxia efficacy, safety, and considerations for use as well as an overview of other potential new tools to control and prevent the growing threat of dengue .

Data-driven computational intelligence applied to dengue outbreak forecasting: a case study at the scale of the city of Natal, RN-Brazil

Dengue is recognized as a health problem that causes significant socioeconomic impacts throughout the world, affecting millions of people each year. A commonly used method for monitoring the dengue vector is to count the eggs that Aedes aegypti mosquitoes have laid in spatially distributed ovitraps. Given this approach, the present study uses a database collected from 397 ovitraps allocated across the city of Natal, RN—Brazil. The Egg Density Index for each neighborhood was computed weekly, over four complete years (from 2016 to 2019), and simultaneously analyzed with the dengue case incidence. Our results illustrate that the incidence of dengue is related to the socioeconomic level of the neighborhoods in the city of Natal. A deep learning algorithm was used to predict future dengue case incidence, either based on the previous weeks of dengue incidence or the number of eggs present in the ovitraps. The analysis reveals that ovitrap data allows earlier prediction (four to six weeks) compared to dengue incidence itself (one week). Therefore, the results validate that the quantification of Aedes aegypti eggs can be valuable for the early planning of public health interventions.

Incidence of dengue fever in Israeli travelers 2008-2019

BACKGROUND

. Dengue virus (DENV) is a frequent travel-related infection, but longitudinal data on its incidence is limited. We aimed to study temporal trends of travel-related DENV burden and its geographical sources.

METHODS

. All cases of laboratory-confirmed DENV infection diagnosed at the Central Virology Laboratory of the Israeli Ministry of Health during 2008-2019 were evaluated. Numbers of Israeli tourist-entries to DENV endemic countries were available from the UN World Tourist Organization (UNWTO) database. DENV attack rates were calculated as cases per 100,000 traveler-entries. In addition, for Thailand and India incidence rates were calculated, using the average duration of stay reported in diagnosed DENV cases.

RESULTS

. During 2008-2019, 425 Israeli travelers were diagnosed with DENV: 80.3%, 12.8% and 6.9% were acquired in Asia, America and Africa respectively. The average global DENV attack rate increased from 2.5 cases per 100,000 tourist-entries in 2008 to 10.7 cases per 100,000 tourist-entries in 2019. Region-specific DENV attack rates were 4.4, 3.2 and 2.1 cases per 100,000 tourist-entries to Asia, Africa, and America respectively. The highest number of DENV cases were reported from Thailand and India; DENV incidence rates increased from 94.5 to 142.2 cases per 100,000 travel-years, and from 49.3 to 90.4 cases per 100,000 travel-years for Thailand and India respectively.

CONCLUSION

. Among Israeli travelers, worldwide DENV attack-rates have quadrupled during 2008-2019, reflecting both a growing DENV burden in Asia, but also the emergence of Africa as an important source of DENV. The need to protect travelers through vaccination remains urgent.

Global burden for dengue and the evolving pattern in the past 30 years

BACKGROUND

Dengue is the most prevalent and rapidly spreading mosquito-borne viral disease. We present the global, regional and national burden of dengue from 1990 to 2019 based on the findings from the Global Burden of Diseases, Injuries, and Risk Factors Study 2019 (GBD 2019).

METHODS

Based upon GBD 2019 dengue data on age-standardized incidence rate (ASIR), age-standardized death rate (ASDR) and age-standardized disability-adjusted life years (DALYs) rate, this study estimates and presents annual percentage change (EAPC) to quantify trends over time to assess potential correlates of increased dengue activity, such as global travel and warming.

RESULTS

Globally from 1990 to 2019, dengue incident cases, deaths and DALYs gradually increased. Those under 5 years of age, once accounting for the largest portion of deaths and DALYs in 1990, were eclipsed by those who were 15-49 years old in 2019. Age standardized incidence [ASIR: EAPC: 3.16, 95% confidence interval (CI): 2.90-3.43], death (ASDR: EAPC: 5.42, 95% CI: 2.64-8.28) and DALY rates (EAPC: 2.31, 95% CI: 2.00-2.62) accelerated most among high-middle and high sociodemographic index (SDI) regions. South-East Asia and South Asia had most of the dengue incident cases, deaths and DALYs, but East Asia had the fastest rise in ASIR (EAPC: 4.57, 95% CI: 4.31, 4.82), while Tropical Latin America led in ASDR (EAPC: 11.32, 95% CI: 9.11, 13.58) and age-standardized DALYs rate (EAPC: 4.13, 95% CI: 2.98, 5.29). SDI showed consistent bell-shaped relationship with ASIR, ASDR and age-standardized DALYs rate. Global land-ocean temperature index and air passenger travel metrics were found to be remarkably positively correlated with dengue burden.

CONCLUSIONS

The burden of dengue has become heavier from 1990 to 2019, amidst the three decades of urbanization, warming climates and increased human mobility in much of the world. South-East Asia and South Asia remain as regions of concern, especially in conjunction with the Americas' swift rise in dengue burden.

Vaccines and Senior Travellers

Background: International tourist travel has been increasingly steadily in recent years, and looks set to reach unprecedented levels in the coming decades. Among these travellers, an increasing proportion is aged over 60 years, and is healthy and wealthy enough to be able to travel. However, senior travellers have specific risks linked to their age, health and travel patterns, as compared to their younger counterparts.

Methods: We review here the risk of major vaccine-preventable travel-associated infectious diseases, and forms and efficacy of vaccination for these diseases.

Results: Routine vaccinations are recommended for older persons, regardless of whether they travel or not (e.g., influenza, pneumococcal vaccines). Older individuals should be advised about the vaccines that are recommended for their age group in the framework of the national vaccination schedule. Travel-specific vaccines must be discussed in detail on a case-by-case basis, and the risk associated with the vaccine should be carefully weighed against the risk of contracting the disease during travel. Travel-specific vaccines reviewed here include yellow fever, hepatitis, meningococcal meningitis, typhoid fever, cholera, poliomyelitis, rabies, Japanese encephalitis, tick-borne encephalitis and dengue.

Conclusion: The number of older people who have the good health and financial resources to travel is rising dramatically. Older travellers should be advised appropriately about routine and travel-specific vaccines, taking into account the destination, duration and purpose of the trip, the activities planned, the type of accommodation, as well as patient-specific characteristics, such as health status and current medications.

Fatal outcomes of imported dengue fever in adult travelers from non-endemic areas are associated with primary infections

BACKGROUND

The case-fatality rate of dengue in travelers is low. Secondary dengue virus (DENV) infections are considered a risk factor for fatal outcome in endemic populations; however, the impact of secondary infections on mortality in travelers has not been studied systematically. We performed a descriptive analysis of case reports of dengue fatalities in travelers.

METHODS

We searched Medline for clinical case reports, using the free terms and MeSH headings: 'Dengue' OR 'Severe Dengue' AND 'Travel-Related Illness' OR 'travel' AND 'Mortality' OR 'Fatal Outcome'. We analyzed case reports of fatal dengue in returning travelers published from 1995 to 2020, with the objective to detail risk factors for dengue mortality in this population. We verified the authors' classifications of primary or secondary dengue infections; infections were considered as primary by absence of anti-DENV immunoglobulin (Ig)G or by IgM-to-IgG ratios greater than or equal to 1.8 in the first 7 days post symptom onset.

RESULTS

We identified nine detailed reports of dengue with fatal outcome among travelers from non-endemic countries. Eight fatalities were female. The median age was 32 years (range 21-63). Out of nine fatal cases, seven travelers had a primary DENV infection, one had a secondary infection and, in one, these data were not reported. The infecting DENV serotypes were DENV-1 (n = 2), DENV-2 (n = 2) and DENV-3 (n = 3); DENV-1 or 2 (n = 1) and in one case, the serotype could not be determined.

CONCLUSIONS

Dengue-related deaths in travelers are rare. Most dengue cases in travelers are primary infections. Contrary to prevailing conceptions, we found that fatal outcomes of dengue in travelers from non-endemic countries were reported mainly with primary DENV infections. We alert health care providers that primary DENV infections are not always harmless and that in adult travelers from non-endemic countries, primary infections may contribute more to dengue-related mortality than secondary infections.

Assessing the Factors of Dengue Transmission in Urban Environments of Pakistan

The rationale of this study is to highlight the significance of relationships of dengue transmission with climate and societal factors for four major cities in Pakistan (i.e., Islamabad, Rawalpindi, Lahore, and Karachi). These cities have been observed to report higher numbers of dengue cases in the last few years, with the highest number of cases reported during 2011. With careful consideration, the relationships of dengue transmission with climate factors, human population density, and traveling in the study areas have been taken into account. Regression model and generalized linear mixed model (GLM) with Markov chain Monte Carlo (MCMC) algorithm are computed to determine the relationships and random effects of different social (human population density, traveling) and climate (minimum-maximum temperatures, and rainfall) factors on dengue transmission. Neural network (NN) with multilayer perceptron algorithm is used to analyze the normalized importance of different covariates relative to dengue transmission. The results show that minimum temperature and rainfall, together with societal factors, significantly affecting the transmission of dengue in the study areas. The magnitude of these relationships is also shown by the results of the neural network. GLM also shows the significant random effects of minimum temperature, rainfall, human population density, and traveling on dengue transmission during the studied years (2009–2018).

A descriptive analysis of dengue in Peace Corps Volunteers, 2000-2019

BACKGROUND

Peace Corps Volunteers (PCVs) are a unique expatriate population at risk for dengue. Previous studies examined travelers or lacked demographic information about expatriates. We examined dengue incidence among PCVs before and after deployment of an electronic medical record (EMR) to assess temporal and demographic factors.

METHODS

Dengue cases within Peace Corps' Epidemiologic Surveillance System from 2000 to 2019 were identified using a standard case definition, and two timeframes were compared: pre-EMR 2000-2015 and post-EMR 2016-2019.

RESULTS

Annual infections occurred in a roughly 3-year cyclic pattern from 2007 to 2019. Incidence rate decreased from 1.35 cases per 100 dengue Volunteer-years (95% CI 1.28-1.41) in 2000-2015 to 1.25 cases (95% CI 1.10-1.41) in 2016-2019. Among PCVs who served from 2016 to 2019, the majority of infections occurred in females and 20-29 year olds, and 7% were medically evacuated. Among PCVs who served from 2015 to 2019, 21% were hospitalized in-country.

CONCLUSIONS

Among PCVs, a non-significant decrease in dengue incidence occurred from 2000-2015 to 2016-2019. Annual infection rates peaked every three years, offering opportunities for targeted prevention efforts. Dengue infection in PCVs appears to mimic the overall demographic of Peace Corps. Expatriates like PCVs are at an increased risk for dengue infection compared to short-term travelers.

Imported arboviral infections in New Zealand, 2001 to 2017: A risk factor for local transmission

BACKGROUND/AIMS

Over the last decade and following international trends, cases of mosquito-borne arboviral infections, notably dengue fever, chikungunya and Zika, have increased among travellers arriving in New Zealand, but no locally acquired cases have been identified. Imported cases are characterised and examined to identify trends and features that might assist in reducing transmission risk from travellers.

METHODS

Information on traveller arrivals, notified cases and risk factors for disease acquisition were obtained from national sources. Trends in importation rates, seasonality are described and relationships of notifications with traveller arrivals were examined with a negative binomial regression model.

RESULTS

There was a significant increase in dengue notifications combined with the emergence of Zika and chikungunya. Most notifications were from arrivals in Auckland from Pacific Islands during summer and early autumn.

CONCLUSION/IMPLICATIONS

Overseas travel from New Zealand, particularly to the Pacific Islands and Southeast Asia, involves a risk of arboviral infection. The repeated introduction of arboviruses to New Zealand also increases the risk of local transmission in a country that has vector capable and vector potential mosquitoes, as well as an increasingly suitable climate for new vectors to establish.

Field Deployment of a Mobile Biosafety Laboratory Reveals the Co-Circulation of Dengue Viruses Serotype 1 and Serotype 2 in Louga City, Senegal, 2017

Dengue virus (DENV) is the most prevalent arboviral threat worldwide. This virus belonging to genus Flavivirus, Flaviviridae family, is responsible for a wide spectrum of clinical manifestations, ranging from asymptomatic or mild febrile illness (dengue fever) to life-threatening infections (severe dengue). Many sporadic cases and outbreaks have occurred in Senegal since 1970. Nevertheless, this article describes a field investigation of suspected dengue cases, between 05 September 2017 and 17 December 2017 made possible by the deployment of a Mobile Biosafety Laboratory (MBS-Lab). Overall, 960 human sera were collected and tested in the field for the presence of viral RNA by real-time RT-PCR. Serotyping, sequencing of complete E gene, and phylogenetic analysis were also performed. Out of 960 suspected cases, 131 were confirmed dengue cases. The majority of confirmed cases were from Louga community. Serotyping revealed two serotypes, Dengue 1 (100/104; 96, 15%) and Dengue 2 (04/104; 3, 84%). Phylogenetic analysis of the sequences obtained indicated that the Dengue 1 strain was closely related to strains isolated, respectively, in Singapore (Asia) in 2013 (KX380803.1) outbreak and it cocirculated with a Dengue 2 strain closely related to strains from a Burkina Faso dengue outbreak in 2016 (KY62776.1). Our results showed the co-circulation of two dengue virus serotypes during a single outbreak in a short time period. This co-circulation highlighted the need to improve surveillance in order to prevent future potential severe dengue cases through antibody-dependent enhancement (ADE). Interestingly, it also proved the reliability and usefulness of the MBS-Lab for expedient outbreak response at the point of need, which allows early cases management.

Decreased dengue transmission in migrant worker populations in Singapore attributable to SARS-CoV-2 quarantine measures

BACKGROUND

We examined the impact of SARS-CoV-2 social distancing and quarantine policies on dengue transmission in the general and migrant worker populations in Singapore.

METHODS

We utilized all nationally reported dengue cases in the general and migrant worker populations from 1 January 2013 to 31 May 2020. A difference-in-difference identification strategy was used to determine the effects of social distancing and quarantine policies on reported dengue case counts over time, whilst controlling for weather patterns, seasonality, age and population size.

RESULTS

A reduction of 4.8 dengue cases per age band among migrant workers was attributable to quarantine policies, corresponding to a total reduction of around 432 reported dengue cases over 10 weeks. In the general working population, an increase of 14.5 dengue cases per age band was observed, which corresponds to a total increase of around 1450 reported dengue cases in the same time period. There is an expected relative risk reduction in dengue transmission for the migrant worker population at 0.635 due to quarantine policy and a relative risk increase for the general working population due to social distancing policies at 0.685.

CONCLUSIONS

Migrant workers experienced a reduced risk of dengue when they were confined to their dormitories as part of the COVID-19 social distancing measures. Our study highlights the vulnerability of migrant workers under normal working conditions.

What Is the Impact of Lockdowns on Dengue?

PURPOSE OF REVIEW

Societal lockdowns in response to the COVID-19 pandemic have led to unprecedented disruption to daily life across the globe. A collateral effect of these lockdowns may be a change to transmission dynamics of a wide range of infectious diseases that are all highly dependent on rates of contact between humans. With timing, duration and intensity of lockdowns varying country-to-country, the wave of lockdowns in 2020 present a unique opportunity to observe how changes in human contact rates, disease control and surveillance affect dengue virus transmission in a global natural experiment. We explore the theoretical basis for the impact of lockdowns on dengue transmission and surveillance then summarise the current evidence base from country reports.

RECENT FINDINGS

We find considerable variation in the intensity of dengue epidemics reported so far in 2020 with some countries experiencing historic low levels of transmission while others are seeing record outbreaks. Despite many studies warning of the risks of lockdown for dengue transmission, few empirically quantify the impact and issues such as the specific timing of the lockdowns and multi-annual cycles of dengue are not accounted for. In the few studies where such issues have been accounted for, the impact of lockdowns on dengue appears to be limited.

SUMMARY

Studying the impact of lockdowns on dengue transmission is important both in how we deal with the immediate COVID-19 and dengue crisis, but also over the coming years in the post-pandemic recovery period. It is clear lockdowns have had very different impacts in different settings. Further analyses might ultimately allow this unique natural experiment to provide insights into how to better control dengue that will ultimately lead to better long-term control.

Dengue, chikungunya and Zika in GeoSentinel surveillance of international travellers: a literature review from 1995 to 2020

INTRODUCTION

GeoSentinel is a global surveillance network of travel medicine providers seeing ill-returned travellers. Much of our knowledge on health problems and infectious encountered by international travellers has evolved as a result of GeoSentinel surveillance, providing geographic and temporal trends in morbidity among travellers while contributing to improved pre-travel advice. We set out to synthesize epidemiological information, clinical manifestations and time trends for dengue, chikungunya and Zika in travellers as captured by GeoSentinel.

METHODS

We conducted a systematic literature search in PubMed on international travellers who presented with dengue, chikungunya or Zika virus infections to GeoSentinel sites around the world from 1995 until 2020.

RESULTS

Of 107 GeoSentinel publications, 42 articles were related to dengue, chikungunya and/or Zika. The final analyses and synthesis of and results presented here are based on the findings from 27 original articles covering the three arboviral diseases.

CONCLUSIONS

Dengue is the most frequent arboviral disease encountered in travellers presenting to GeoSentinel sites, with increasing trends over the past two decades. In Southeast Asia, annual proportionate morbidity increased from 50 dengue cases per 1000 ill returned travellers in non-epidemic years to an average of 159 cases per 1000 travellers during epidemic years. The highest number of travellers with chikungunya virus infections was reported during the chikungunya outbreak in the Americas and the Caribbean in the years 2013-16. Zika was first reported by GeoSentinel already in 2012, but notifications peaked in the years 2016-17 reflecting the public health emergency in the Americas at the time.

The first licensed dengue vaccine: can it be used in travelers?

PURPOSE OF REVIEW

The first dengue vaccine (Dengvaxia) was endorsed by the European Medicine Agency and the US Food and Drug Administration. Given the excess risk of severe dengue in seronegative vaccinees, use is restricted to seropositive individuals. Dengvaxia confers high protection against severe dengue in seropositive vaccinees.

RECENT FINDINGS

With increasing global travel, the probability of travelers being seropositive increases. Such seropositive travelers may be at increased risk of severe dengue as a result of a second dengue infection during repeat travel. Nevertheless, the use of Dengvaxia in travelers requires a careful analysis of all the factors. Seropositive travelers only present a minority of all travelers. A validated rapid diagnostic test to screen for dengue serostatus is not yet available. Such a test should be highly specific to avoid inadvertent vaccination of seronegative individuals. The three-dose regimen precludes the use in most travelers who tend to present at travel clinics less than 6 weeks prior to departure. Furthermore, questions about potential sub-optimal immunogenicity in seropositives in nonendemic settings, and the need and timing of boosters remain unanswered.

SUMMARY

Although there could potentially be substantial protection against severe dengue in seropositive travelers, Dengvaxia is far from an ideal travel vaccine.

The effects of climate change on infectious diseases with cutaneous manifestations

Background

Anthropogenic climate change affects the burden of infectious diseases via several interconnected mechanisms. In recent years, there has been greater awareness of the ways in which climate-sensitive infectious diseases pose a growing threat to global public health.

Objective

This study aimed to categorize and describe the effects of climate change on infectious diseases with skin manifestations.

Methods

A scoping review of the MEDLINE and PubMed online databases for climate-sensitive infections was performed in February and March 2020. A representative selection of conditions with skin manifestations was included in this review.

Results

Several representative climate-sensitive infectious diseases were identified in each of the following categories: vector-borne infectious diseases, infectious diseases associated with extreme weather events, and infectious diseases linked to human migration.

Conclusion

Climate variables directly influence the survival and reproduction of infectious microorganisms, their vectors, and their animal reservoirs. Due to sustained warmer temperatures at higher latitudes, climate change has expanded the geographic range of certain pathogenic microbes. More frequent climate change-related extreme weather events create circumstances where existing infectious microorganisms flourish and novel infections emerge. Climate instability is linked to increased human migration, which disrupts health care infrastructure as well as the habitats of microbes, vectors, and animal reservoirs and leads to widespread poverty and overcrowding. Dermatologists should understand that climate change will affect the burden and geographic distribution of infectious diseases, many of which have cutaneous signs and might be encountered in their regular practice.

Risks Related to Chikungunya Infections among European Union Travelers, 2012-2018

Autochthonous outbreaks of chikungunya have occurred in the European Union (EU) after virus introduction by infected travelers. We reviewed the surveillance data of travel-related cases reported in the EU during 2012–2018 to document factors associated with increased infection rates among travelers and to assess how surveillance data could support preparedness against secondary transmission and timely control of outbreaks. Thirteen EU countries reported 2,616 travel-related chikungunya cases. We observed 3 successive epidemiologic periods; the highest number of cases (75%) occurred during 2014–2015, when most cases were associated with the Caribbean and South America. The highest infection rates among travelers were observed during the same phase. Although surveillance of travel-related cases is relevant for estimating the infection risk for travelers, we could not identify a relationship between the number of infected travelers and a higher likelihood of secondary transmission in the EU.

Epidemiology of Dengue, Chikungunya, and Zika Virus Disease in U.S. States and Territories, 2017

Dengue, chikungunya, and Zika viruses, primarily transmitted by Aedes species mosquitoes, have caused large outbreaks in the Americas, leading to travel-associated cases and local mosquito-borne transmission in the United States. We describe the epidemiology of dengue, chikungunya, and noncongenital Zika virus disease cases reported from U.S. states and territories in 2017, including 971 dengue cases, 195 chikungunya cases, and 1,118 Zika virus disease cases. Cases of all three diseases reported from the territories were reported as resulting from local mosquito-borne transmission. Cases reported from the states were primarily among travelers, with only seven locally acquired mosquito-transmitted Zika virus disease cases reported from Texas (n = 5) and Florida (n = 2). In the territories, most dengue cases (n = 508, 98%) were reported from American Samoa, whereas the majority of chikungunya (n = 39, 100%) and Zika virus disease (n = 620, 93%) cases were reported from Puerto Rico. Temporally, the highest number of Zika virus disease cases occurred at the beginning of the year, followed by a sharp decline, mirroring decreasing case numbers across the Americas following large outbreaks in 2015 and 2016. Dengue and chikungunya cases followed a more seasonal pattern, with higher case numbers from July through September. Travelers to the United States and residents of areas with active virus transmission should be informed of both the ongoing risk from dengue, chikungunya, and Zika virus disease and personal protective measures to lower their risk of mosquito bites and to help prevent the spread of these diseases.

A Prospective Study on the Impact and Out-of-Pocket Costs of Dengue Illness in International Travelers

Although the costs of dengue illness to patients and households have been extensively studied in endemic populations, international travelers have not been the focus of costing studies. As globalization and human travel activities intensify, travelers are increasingly at risk for emerging and reemerging infectious diseases, such as dengue. This exploratory study aims to investigate the impact and out-of-pocket costs of dengue illness among travelers. We conducted a prospective study in adult travelers with laboratory-confirmed dengue and recruited patients at travel medicine clinics in eight different countries from December 2013 to December 2015. Using a structured questionnaire, we collected information on patients and their health-care utilization and out-of-pocket expenditures, as well as income and other financial losses they incurred because of dengue illness. A total of 90 patients participated in the study, most of whom traveled for tourism (74%) and visited countries in Asia (82%). Although 22% reported hospitalization and 32% receiving ambulatory care while traveling, these percentages were higher at 39% and 71%, respectively, after returning home. The out-of-pocket direct and indirect costs of dengue illness were US$421 (SD 744) and US$571 (SD 1,913) per episode, respectively, averaging to a total out-of-pocket cost of US$992 (SD 2,052) per episode. The study findings suggest that international travelers incur important direct and indirect costs because of dengue-related illness. This study is the first to date to investigate the impact and out-of-pocket costs of travel-related dengue illness from the patient's perspective and paves the way for future economic burden studies in this population.

Imported dengue in Spain: a nationwide analysis with predictive time series analyses

BACKGROUND

Of febrile illnesses in Europe, dengue is second only to malaria as a cause of travellers being hospitalized. Local transmission has been reported in several European countries, including Spain. This study assesses the evolution of dengue-related admissions in Spain in terms of time, geographical distribution and individuals' common characteristics; it also creates a predictive model to evaluate the risk of local transmission.

METHODS

This is a retrospective study using the Hospital Discharge Records Database from 1997 to 2016. We calculated hospitalization rates and described clinical characteristics. Spatial distribution and temporal behaviour were also assessed, and a predictive time series model was created to estimate expected cases in the near future. Figures for resident foreign population, Spanish residents' trips to endemic regions and the expansion of Aedes albopictus were also evaluated.

RESULTS

A total of 588 dengue-related admissions were recorded: 49.6% were women, and the mean age was 34.3 years. One person died (0.2%), 82% presented with mild-to-moderate dengue and 7-8% with severe dengue. We observed a trend of steady and consistent increase in incidence (P < 0.05), in parallel with the increase in trips to dengue-endemic regions. Most admissions occurred during the summer, showing significant seasonality with 3-year peaks. We also found important regional differences. According to the predictive time series analysis, a continuing increase in imported dengue incidence can be expected in the near future, which, in the worst case scenario (upper 95% confidence interval), would mean an increase of 65% by 2025.

CONCLUSION

We present a nationwide study based on hospital, immigration, travel and entomological data. The constant increase in dengue-related hospitalizations, in combination with wider vector distribution, could imply a higher risk of autochthonous dengue transmission in the years to come. Strengthening the human and vector surveillance systems is a necessity, as are improvements in control measures, in the education of the general public and in fostering their collaboration in order to reduce the impact of imported dengue and to prevent the occurrence of autochthonous cases.

Severe dengue in travellers: pathogenesis, risk and clinical management

RATIONALE FOR REVIEW

Dengue is a frequent cause of febrile illness among travellers and has overtaken malaria as the leading cause of febrile illness for those traveling to Southeast Asia. The purpose is to review the risk of dengue and severe dengue in travellers with a particular focus on the pathogenesis and clinical management of severe dengue.

RISK, PATHOGENESIS AND CLINICAL MANAGEMENT

The risk of travel-acquired dengue depends on destination, season and duration of travel and activities during travel. Seroconversion rates reported in travellers, therefore, vary between <1% and >20%. The most common life-threatening clinical response to dengue infection is the dengue vascular permeability syndrome, epidemiologically linked to secondary infection, but can also occur in primary infection. Tertiary and quaternary infections are usually associated with mild or no disease. Antibody-dependent enhancement, viral factors, age, host factors and clinical experience of the managing physician modulate the risk of progressing to severe dengue. The relative risk of severe dengue in secondary versus primary infection ranges from 2 to 7. The absolute risk of severe dengue in children in highly endemic areas is ~0.1% per year for primary infections and 0.4% for secondary infections. About 2-4% of secondary infections lead to severe dengue. Severe dengue and death are both relatively rare in general travellers but more frequently in those visiting friends and relatives. Clinical management of severe dengue depends on judicious use of fluid rehydration.

CONCLUSIONS

Although dengue is a frequent cause of travel illness, severe dengue and deaths are rare. Nevertheless, dengue infections can interrupt travel and lead to evacuation and major out-of-pocket costs. Dengue is more frequent than many other travel-related vaccine preventable diseases, such as hepatitis A, hepatitis B, rabies, Japanese encephalitis and yellow fever, indicating a need for a dengue vaccine for travellers.

Travel Surveillance and Genomics Uncover a Hidden Zika Outbreak during the Waning Epidemic

The Zika epidemic in the Americas has challenged surveillance and control. As the epidemic appears to be waning, it is unclear whether transmission is still ongoing, which is exacerbated by discrepancies in reporting. To uncover locations with lingering outbreaks, we investigated travel-associated Zika cases to identify transmission not captured by reporting. We uncovered an unreported outbreak in Cuba during 2017, a year after peak transmission in neighboring islands. By sequencing Zika virus, we show that the establishment of the virus was delayed by a year and that the ensuing outbreak was sparked by long-lived lineages of Zika virus from other Caribbean islands. Our data suggest that, although mosquito control in Cuba may initially have been effective at mitigating Zika virus transmission, such measures need to be maintained to be effective. Our study highlights how Zika virus may still be "silently" spreading and provides a framework for understanding outbreak dynamics. VIDEO ABSTRACT.

Cosmopolitan A1 lineage of dengue virus serotype 2 is circulating in Pakistan: A study from 2017 dengue viral outbreak

Dengue viral infection has become a challenge in tropical and subtropical countries where dengue virus is endemic. Its epidemics are occurring at higher rates amid its circulation throughout the year. Since the first documented outbreak in Pakistan in 1994, this region has reported many sporadic cases and epidemics. There is availability of small scale demographic and epidemiological studies on dengue viral infection in Pakistan. The year 2017 witnessed a huge dengue outbreak in Peshawar city of Pakistan with 69 deaths and 24 807 laboratory-confirmed cases. We suspect that the circulation of a different lineage or genotype could be responsible for the enhanced number of infected patients in Pakistan's 2017 outbreak since previous studies have already described this phenomenon in other countries. For this, we collected 1447 suspected blood samples and their epidemiological data. After serotyping through polymerase chain reaction nine samples of Dengue virus2 (DENV2) were randomly selected and were subjected to Sanger's sequencing for genotyping analysis. The mean distance, genetic diversity, and phylogenetic analysis were carried out using K2 model. The phylogenetic analysis split Pakistani isolates into two lineages, the sequences from 2017 outbreak in Peshawar grouped within A1 lineage of cosmopolitan genotype (IV) of DENV2. The difference in distance, genetic diversity, and amino acids composition strongly back the results that the new lineage is circulating in the region. This is significant as Pakistan is struggling to control dengue epidemics which have caused much loss in both monetary and health sectors.

Structure-based screening and validation of potential dengue virus inhibitors through classical and QM/MM affinity estimation

The recurrent outbreaks of dengue virus around the globe represent a huge challenge for governments and public health organizations. With the rapid growth and ease of transportation, dengue disease continues to spread, placing more of the world population under constant threat. Despite decades of research efforts, no effective small molecule antivirals are available against dengue virus. With the efficacy of the recently developed vaccine to be determined, there is an urgent unmet need for small molecule dengue virus treatments. In the current study, we employed state-of-the-art molecular modelling simulations to identify novel inhibitors of the dengue virus envelope protein. The binding modes of all compounds within the conserved β-OctylGlucoside (β-OG) pocket were studied using a combination of docking, molecular dynamics simulations and binding free energy calculations. Here, we describe ten new compounds that significantly reduce production of dengue virus as determined using standard cell-based virological assays. Moreover, we present a comprehensive structural analysis of the identified hits, focusing on their electrostatic and lipophilic binding energy contributions. Finally, we highlight the effect of the desolvation penalty in limiting the activity of some of these compounds. The data presented here paves the way toward rationally designing selective and potent novel inhibitors against dengue virus.

Can dengue virus be sexually transmitted?

Can dengue virus be sexually transmitted? A literature review revealed one probable case of female-to-male transmission. Even if dengue PCR can occasionally be found in semen or vaginal secretions, reports on sexual transmission are extremely rare. Sexual transmission of DENV has no public health significance.

Using Multiple Scale Space-Time Patterns in Variance-Based Global Sensitivity Analysis for Spatially Explicit Agent-Based Models

Sensitivity analysis (SA) in spatially explicit agent-based models (ABMs) has emerged to address some of the challenges associated with model specification and parameterization. For spatially explicit ABMs, the comparison of spatial or spatio-temporal patterns has been advocated to evaluate models. Nevertheless, less attention has been paid to understanding the extent to which parameter values in ABMs are responsible for mismatch between model outcomes and observations. In this paper, we propose the use of multiple scale space-time patterns in variance-based global sensitivity analysis (GSA). A vector-borne disease transmission model was used as the case study. Input factors used in GSA include one related to the environment (introduction rates), two related to interactions between agents and environment (level of herd immunity, mosquito population density), and one that defines agent state transition (mosquito extrinsic incubation period). The results show parameters related to interactions between agents and the environment have great impact on the ability of a model to reproduce observed patterns, although the magnitudes of such impacts vary by space-time scales. Additionally, the results highlight the time-dependent sensitivity to parameter values in spatially explicit ABMs. The GSA performed in this study helps in identifying the input factors that need to be carefully parameterized in the model to implement ABMs that well reproduce observed patterns at multiple space-time scales.

Dengue Situation in Bangladesh: An Epidemiological Shift in terms of Morbidity and Mortality

The escalating dengue situation in Bangladesh has been emerging as a serious public health problem in terms of morbidity and mortality. Results of analysis of 40,476 cases of Bangladesh occurring during 2000-2017 indicated that 49.73% of the dengue cases occurred during the monsoon season (May-August) and 49.22% during the post-monsoon season (September-December). However, data also showed that, since 2014, these trends have been changing, and dengue cases have been reported during the pre-monsoon season. During 2015-2017, in the pre-monsoon season, the dengue cases were reported to be more than seven times higher compared to the previous 14 years. The findings closely correlate with those of the pre-monsoon Aedes vector survey which revealed the presence of high density of larva and pupa of the dengue vectors in the environment all the year round. In our study, climate changes, such as average rainfall, humidity, and temperature, after 2014, and rapid unplanned urbanization were the strong predictors of an imbalance in the existing ecology that has led to increase in dengue cases in 2016 and the emergence of the chikungunya virus for the first time in Bangladesh in 2017. Although 2018 dengue data are relevant but not included in this study due to study time frame, it is interesting to report an increase in the number of dengue cases in pre (2016) and post (2018, which is highest within 18 years) chikungunya outbreak, which favors the study hypothesis. Despite the efforts to control dengue, based primarily on the vector control and case management, the burden and costs of the disease and similar vector-borne diseases will continue to grow in future in our country. Developing a cost-effective vaccine against all the 4 strains of dengue remains a challenge. The CDC, in collaboration with other research organizations, may come forward to initiate and coordinate a large-scale randomized clinical trial of an effective dengue vaccine in Bangladesh.

[Dengue fever : Symptoms, epidemiology, entomology, pathogen diagnosis and prevention]

Dengueinfektionen gehören zu den häufigsten Ursachen fieberhafter Erkrankungen im tropischen Umfeld. Die Infektion wird durch ein Flavivirus verursacht, das durch Aedes-Moskitos übertragen wird. Hauptüberträger für Dengueviren sind die weltweit in den Tropen verbreiteten Aedes-aegypti-Stechmücken. Da diese einerseits tagaktiv und andererseits sog. „container breeder“ sind, bedarf es besonderer Vorbeugungs- und Bekämpfungsmaßnahmen. Die Schwere der Symptomatik variiert und kann vom milden grippeähnlichen klinischen Bild bis hin zu schweren Hämorrhagien und Schock reichen. Zu den häufigsten Symptomen bei Reisenden gehören Fieber, Muskelschmerzen, Kopfschmerzen und Hautausschlag. Zur Diagnostik kommen, in Abhängigkeit vom Stadium der Infektion, patientennah einsetzbare Schnellteste oder – in der virämischen Phase – molekulare Erregerdirektnachweise infrage. Die serologische Diagnostik ist aufgrund von serologischen Kreuzreaktionen mit anderen Flaviviren hinsichtlich ihrer Interpretation anspruchsvoll.

Dengue

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

Pretravel Considerations for Non-vaccine-Preventable Travel Infections

Pretravel advice should be tailored to the individual following a thorough review of his or her itinerary, planned activities, and host characteristics. In addition to vaccinations and malaria chemoprophylaxis, a pretravel consultation should include advice on regionally endemic or emerging non–vaccine-preventable infections that can cause severe illness or chronic morbidity. These include mosquito-borne infections such as dengue, chikungunya, and Zika, and regionally endemic severe respiratory infections such as Middle East respiratory syndrome (MERS) and some strains of avian influenza. Zika virus is notable given its capacity for sexual transmission and association with congenital birth defects. Preventive advice for other potentially relevant infections associated with specific exposures or activities (e.g., schistosomiasis and leptospirosis from freshwater exposure) should be provided where relevant. Understanding the epidemiology and prevention of these infections is crucial to providing a comprehensive pretravel consultation.

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Pretravel advice should be tailored to the individual following a thorough review of his or her itinerary, planned activities, and host characteristics.

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The pretravel consultation should include preventive advice for regionally endemic non–vaccine-preventable infections that can cause severe illness or chronic morbidity.

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Special consideration should be given to common or emerging arboviral infections (including dengue, chikungunya, and Zika) and regionally endemic severe respiratory infections such as Middle East respiratory syndrome (MERS) and certain strains of avian influenza.

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Preventive advice for other infections associated with specific exposures or activities should be provided where relevant.

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Understanding the epidemiology and prevention of these infections is crucial to providing a comprehensive pretravel consultation.

Bayesian compartmental model for an infectious disease with dynamic states of infection

Population-level proportions of individuals that fall at different points in the spectrum [of disease severity], from asymptomatic infection to severe disease, are often difficult to observe, but estimating these quantities can provide information about the nature and severity of the disease in a particular population. Logistic and multinomial regression techniques are often applied to infectious disease modeling of large populations and are suited to identifying variables associated with a particular disease or disease state. However, they are less appropriate for estimating infection state prevalence over time because they do not naturally accommodate known disease dynamics like duration of time an individual is infectious, heterogeneity in the risk of acquiring infection, and patterns of seasonality. We propose a Bayesian compartmental model to estimate latent infection state prevalence over time that easily incorporates known disease dynamics. We demonstrate how and why a stochastic compartmental model is a better approach for determining infection state proportions than multinomial regression is by using a novel method for estimating Bayes factors for models with high-dimensional parameter spaces. We provide an example using visceral leishmaniasis in Brazil and present an empirically-adjusted reproductive number for the infection.

Vertical transmission of dengue virus in the Yogyakarta airport area

Background

International Health Regulations controls international travel including human movement, disease vector, and imported items to prevent the spread of dengue, especially in seaports, airports, and border crossing posts. This study aimed to determine dengue Transovarial Transmission Index (TTI) and distribution of dengue virus in the areas around Adisucipto Airport of Yogyakarta, Indonesia.

Methods

The study was a descriptive analytic study with cross sectional design, conducted by mapping the spread of the dengue virus and identifying TTI in Adisucipto Airport. A total of 145 ovitraps were installed in both perimeter and buffer areas of the airport. Positive Ovitrap Index (OI), TTI, and serotype of dengue virus were examined. The TTI was identified using immunocytochemistry immunoperoxidase streptavidin biotin complex (IISBC) method in mosquito head squash preparations.

Results

OI in the buffer area was 32 (45.1%), whereas OI in the perimeter area was 24 (32.4%). The TTI in the buffer and perimeter areas were 21 (18.3%) and 11 (18.9%), respectively. The TTI was found greater in the Aedes aegypti population compared to the Aedes albopictus population, both in the perimeter area (20% versus 16.7%) and the buffer area (20.3% versus 16.1%). Dengue virus serotype-2 (DENV-2) and dengue virus serotype-3 (DENV-3) were predominantly found in Ae. aegypti and Ae. albopictus.

Conclusions

Buffer areas of Adisucipto Airport of Yogyakarta have higher risk as breeding sites for Aedes spp., predominantly DENV-2 and DENV-3 serotypes. High OI shows that the areas are likely to have higher risk of developing dengue outbreak.

Co-circulation of all the four dengue virus serotypes and detection of a novel clade of DENV-4 (genotype I) virus in Pune, India during 2016 season

Dengue is the most common mosquito-borne viral infection in tropical and sub-tropical countries. In recent years, India has reported increased incidences of concurrent infection with multiple serotypes of dengue viruses (DENV). In the present study, we have characterized DENV circulating during a single season of 2016 in Pune, India. A total of 64 serum samples from NS1 ELISA positive dengue patients were used for PCR amplification of CprM region of the viral genome and sequencing. Phylogenetic analysis documented circulation of all the four DENV serotypes with predominance of DENV-2 (40.6%). DENV genotyping classified DENV-1 to Genotype V, DENV-2 to Genotype IV, DENV-3 to Genotype III and DENV-4 to Genotype I. Further analysis revealed emergence of a novel clade (D) of genotype I of DENV-4. Subsequent isolation of three DENV-4 viruses in cell culture followed by complete genome sequence analysis confirmed this observation. Additionally, a new genotype within serotype-4 with >6.7% sequence variation from other genotypes was identified. This first report of significant co-circulation of all the four serotypes in a single outbreak in Pune reconfirms need for molecular monitoring of DENV.

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.

The Epidemiology of Imported Acute Infectious Diseases in Zhejiang Province, China, 2011-2016: Analysis of Surveillance Data

To explore epidemiological characteristics of imported acute infectious diseases between 2011 and 2016 in Zhejiang province, China. Data of imported infectious diseases from 2011 to 2016 was collected from the China Information System for Disease Control and Prevention in Zhejiang province, and subsequently analyzed for epidemiological characteristics. A survey was conducted to investigate clinicians' abilities to diagnose these diseases in Zhejiang province. From 2011 to 2016, 1,241 cases of imported acute infectious disease were reported in Zhejiang province, including 1,078 malaria cases, 156 dengue cases, three chikungunya fever cases and four Zika cases. Between 2011 and 2016, incidences of these diseases increased (P < 0.001). For malaria, male adults for labor export were the most affected group. Seasonal fluctuation was not obvious. Plasmodium falciparum was the main malaria type (822 cases) and most cases were acquired from African Region (791/822, 96.1%). Plasmodium vivax cases (194 cases) were mainly from African Region (78/194, 40.2%) and South-East Asia Region (51/194, 26.3%). Meanwhile, for dengue, adults and tourists were the most affected groups. The incidence of dengue was particularly high in August and October. The percent of correct clinician responses in the survey of diagnosis knowledge was 54.6% (standard deviation = 21.0%); this percentage was particularly low in general practitioners and clinicians from township hospitals. The capabilities of clinicians to diagnose these diseases were low and should be improved. Efforts should be made in improving and disseminating proper preventive measures of high-risk populations, surveillance of imported cases, and prevention and control of local epidemics.

Importation of travel-related infectious diseases is increasing in South Korea: An analysis of salmonellosis, shigellosis, malaria, and dengue surveillance data

BACKGROUND

International travel has an important role in transmission of emerging infectious diseases. We described the imported infectious diseases in Korea from 2003 to 2012, and to analyze association of travels with the change in the incidences.

METHODS

We used National Notifiable Disease Surveillance System to investigate the incidence of salmonellosis, shigellosis, malaria, and dengue. Data from Korea Tourism Organization was used to describe the inbound and outbound travelers by their age group, gender, and purpose of travel. We assessed association between international travel and the incidence of the infectious diseases, and seasonal variability.

RESULTS

Among 1849 imported cases, dengue comprised the largest number with 631 cases. The proportion of imported cases among total cases gradually increased from 4.1% in 2003 to 30.3% in 2012 (P < 0.001). There was a positive correlation between the number of travelers and the number of imported cases of shigellosis, dengue (P < 0.001), but not for malaria. Seasonal variability was observed for importation of salmonellosis, shigellosis and dengue fever (P = 0.005).

CONCLUSION

International travel was associated with the incidence of imported infectious diseases in Korea. Pre-travel consultation for international travelers planned to visit endemic area should be recommended strongly.

Redefining priorities towards graded travel-related infectious disease research

Our knowledge of the health problems and infections encountered by international travellers has evolved considerably in the past decades. The growth of global networks such as the GeoSentinel Surveillance network, TropNet Europe, EuroTravNet and networks based in North America have provided valuable information on the frequency of a wide array of travel-related diseases and accidents, including details on the destination of travel and trends over time. The information gained from these network studies has provided important data for the practice of travel medicine and in some instances for the development of practice guidelines. However, network data due to a lack of denominators usually cannot serve as a basis for a GRADE approach to guideline development. Although epidemiological network studies will continue to serve an important role in travel medicine we encourage an additional strong focus towards translational scientific research questions and towards the broader use of novel techniques to obtain more accurate epidemiological analyses to address the many unanswered questions in our field.

Imported dengue fever in East London: a 6-year retrospective observational study

BACKGROUND

Dengue fever (DF) is a frequently imported arthropod-borne infection in the United Kingdom but its broad range of clinical presentations makes it potentially unrecognized by clinicians.

METHODS

We conducted a 6-year retrospective case note review of laboratory confirmed DF patients in East London in the period from 1 January 2010 through 31 December 2015. Epidemiological, clinical and laboratory features of imported DF were described. Risk factors associated with viraemic DF presentations were assessed.

RESULTS

Forty-four patients (4 from primary care clinics and 40 from three acute hospitals) were confirmed to have DF through RNA and/or IgM detection. In total, 86.4% (38/44) had primary infection compared to 13.6% (6/44) with secondary infection. Viraemic DF presentations accounted for 59.1% (26/44) of cases. The median age was 34 years (IQR 25-43). Most patients were males (68.2%, 30/44) and of non-white ethnicity (81.8%, 36/44). South Asia was the most frequent travel destination (52.3%, 23/44) followed by Southeast Asia (20.5%, 9/44). July-September was the peak season of presentation (43.2%, 19/44). The median interval between arrival in the UK and laboratory testing was 7 days (IQR 4-13). Arriving from abroad ≤ 7 days before molecular testing (age-adjusted odds ratios [OR] 16.98, 95% CI 2.43-118.75, P  =   0.004) and travel to South or Southeast Asia regions (age-adjusted OR 4.41, 95% CI 1.07-18.21, P  =   0.040) were associated with detectable viraemia at presentation. Only one DF patient met the WHO severity criteria. HIV serostatus was determined in 61.4% (27/44) of cases.

CONCLUSION

Clinicians need to improve DF recognition as well as rates of HIV testing in tropical travellers. Region of travel and time since arrival from DF endemic settings may help clinicians optimize requests for molecular testing. Further research on the clinical and public health aspects of imported DF is needed.