Epidemiology of dengue virus infections in Nepal, 2006-2019

Climate-driven dengue fever outbreaks in Nepal: Trends, challenges, and strategies

Dengue fever (DF) has become a major public health concern in Nepal, with increasing outbreaks in recent years. Transmitted by Aedes mosquitoes, this climate-sensitive viral disease presents a significant challenge for healthcare providers and policymakers. Since 2004, Nepal has experienced a sharp increase in DF cases, peaking in 2022 with 54784 cases and 88 deaths. The surge, driven mainly by serotypes 1, 2, and 3, is exacerbated by climate change, which prolongs mosquito breeding seasons due to warmer temperatures and increased rainfall. This trend has even impacted previously unaffected hilly regions. Effective dengue control strategies must focus on climate change adaptation, strengthening healthcare system reinforcement, raising public awareness, and enhancing vector control measures. Government initiatives, like the national dengue control program, play a critical role, but research and community engagement are also vital for prevention and early detection. Integrating climate resilience into public health efforts is essential to reducing the dengue burden in Nepal.

Entomological surveillance of container-breeding mosquitoes focusing on Aedes (Stegomyia) (Diptera: Culicidae) vectors along altitudinal range in Nepal

Mosquitoes are a significant public health concern due to their role in transmitting various diseases. This study aimed to investigate mosquitoes' diversity, abundance, and ecological aspects, mainly focusing on Aedes (Diptera: Culicidae) mosquitoes, in central Nepal. The research explored variations across regions, seasons, altitudes, and years. Fieldwork for mosquito collection was conducted between May 2022 and October 2023. Dipping and pipetting methods were employed to collect larvae and pupae, whereas Biogents-Mosquitaire trap captured adult mosquitoes. A total of 7,223 (3,640 larvae and 3,583 adults) mosquitoes, belonging to 8 genera and 18 species, were collected and analyzed. Additionally, a survey examined 5,941 wet containers of 20 different types to assess potential breeding sites. The study revealed Culex pipiens (Linnaeus, 1758) (34.13%) and Aedes albopictus (Skuse, 1895) (27.36%) as the most abundant species. Interestingly, larvae were predominantly Aedes spp. (66.13%), whereas only 13.76% of adults belonged to this genus. Mosquito abundance varied across locations and altitudes, with Siwalik region (331-700 m asl) exhibiting the highest numbers. The monsoon season showed the highest overall abundance (1,492). Used tires were identified as significant breeding sites for Aedes mosquitoes, and infestation rates were higher in shaded containers. Seasonal analysis showed the House Index (HI) reaching its peak (10.92%) and the Breteau Index (BI) reaching 23.08% during the monsoon. Conversely, the Container Index (CI) reached its highest point (37.67%) in the post-monsoon season. The results emphasize the need for comprehensive disease prevention strategies at local and national levels, including public awareness campaigns, to address mosquito-borne illnesses in this famous tourist region.

Dengue virus surveillance in Nepal yields the first on-site whole genome sequences of isolates from the 2022 outbreak

BACKGROUND

The 4 serotypes of dengue virus (DENV1-4) can each cause potentially deadly dengue disease, and are spreading globally from tropical and subtropical areas to more temperate ones. Nepal provides a microcosm of this global phenomenon, having met each of these grim benchmarks. To better understand DENV transmission dynamics and spread into new areas, we chose to study dengue in Nepal and, in so doing, to build the onsite infrastructure needed to manage future, larger studies.

METHODS AND RESULTS

During the 2022 dengue season, we enrolled 384 patients presenting at a hospital in Kathmandu with dengue-like symptoms; 79% of the study participants had active or recent DENV infection (NS1 antigen and IgM). To identify circulating serotypes, we screened serum from 50 of the NS1+ participants by RT-PCR and identified DENV1, 2, and 3 - with DENV1 and 3 codominant. We also performed whole-genome sequencing of DENV, for the first time in Nepal, using our new on-site capacity. Sequencing analysis demonstrated the DENV1 and 3 genomes clustered with sequences reported from India in 2019, and the DENV2 genome clustered with a sequence reported from China in 2018.

CONCLUSION

These findings highlight DENV's geographic expansion from neighboring countries, identify China and India as the likely origin of the 2022 DENV cases in Nepal, and demonstrate the feasibility of building onsite capacity for more rapid genomic surveillance of circulating DENV. These ongoing efforts promise to protect populations in Nepal and beyond by informing the development and deployment of DENV drugs and vaccines in real time.

Investigating public understanding and actions regarding Aedes mosquitoes and dengue prevention across altitudinal range in central Nepal

BACKGROUNDS OBJECTIVES

Dengue fever, transmitted by Aedes mosquitoes, is a significant public health concern in Nepal. An extensive Knowledge, Attitude, and Practice (KAP) survey related to Aedes mosquitoes and prevention of dengue was conducted along the route from Matihani (62 m above sea level) to Kalinchok (3840 m asl) in central Nepal. This research examined residents' awareness of Aedes mosquitoes and the diseases they transmit, aiming to support the World Health Organization's national and global fight against mosquito-borne diseases.

METHODS

The survey included 550 participants aged 18-75 years (249 males and 201 females). Door-to-door campaigns were conducted to gather data on knowledge scores, practices, and attitudes about Aedes mosquitoes using a standard structured questionnaire.

RESULTS

Findings of this study revealed a moderate level of knowledge across the study area, with a mean knowledge score of 5.525±2.58 (correct answer rate of 46.05%). While 99.6% of respondents were aware of dengue transmission by mosquitoes, only 64.5% were able to report Aedes mosquitoes as the key transmitter. Less than one-third of the participants (27.8%) were familiar with black-and-white stripes in Aedes. Additionally, only 36.7% were knowledgeable about the day-biting behavior of Aedes mosquitoes.

INTERPRETATION CONCLUSION

This KAP survey provides valuable insights into community understanding of Aedes mosquitoes and dengue prevention practices associated with various Nepalese communities residing in low to high altitudes of central Nepal. These findings can be adopted to address the increasing health burden faced by countries with low-to-high altitude regions within the Hindu Kush Himalayas.

Genomic sequencing and neutralizing serological profiles during acute dengue infection: A 2017 cohort study in Nepal

Dengue virus (DENV) is a mosquito-borne flavivirus that poses a threat to nearly 50% of the global population. DENV has been endemic in Nepal since 2006; however, little is known about how DENV is evolving or the prevalence of anti-DENV immunity within the Nepalese population. To begin to address these gaps, we performed a serologic and genetic study of 49 patients from across Nepal who presented at central hospitals during the 2017 dengue season with suspected DENV infection. Of the 49 subjects assessed, 21 (43%) were positive for DENV NS1 antigen; of these; 5 were also anti-DENV IgM + IgG + ; 7 were DENV IgM + IgG - , 2 were IgM - IgG + , and 7 were IgM - IgG - by specific ELISAs. Seven of the 21 NS1+ sera were RNA+ by RT-PCR (six DENV2, one DENV3), suggesting that DENV2 was the dominant serotype in our cohort. Whole-genome sequencing of two DENV2 isolates showed similarity with strains circulating in Singapore in 2016, and the envelope genes were also similar to strains circulating in India in 2017. DENV-neutralizing antibodies (nAbs) were present in 31 of 47 sera tested (66%); among these, 20, 24, 26, and 12 sera contained nAbs against DENV1, 2, 3, and 4 serotypes, respectively. Serology analysis suggested that 12 (26%) and 19 (40%) of the 49 subjects were experiencing primary and secondary DENV infections, respectively. Collectively, our results provide evidence for current and/or past exposure to multiple DENV serotypes in our cohort, and the RNA analyses further indicate that DENV2 was the likely dominant serotype circulating in Nepal in 2017. These data suggest that expanded local surveillance of circulating DENV genotypes and population immunity will be important to effectively manage and mitigate future dengue outbreaks in Nepal.

Dengue Virus Surveillance in Nepal Yields the First On-Site Whole Genome Sequences of Isolates from the 2022 Outbreak

Background

The 4 serotypes of dengue virus (DENV1-4) can each cause potentially deadly dengue disease, and are spreading globally from tropical and subtropical areas to more temperate ones. Nepal provides a microcosm of this global phenomenon, having met each of these grim benchmarks. To better understand DENV transmission dynamics and spread into new areas, we chose to study dengue in Nepal and, in so doing, to build the onsite infrastructure needed to manage future, larger studies.

Methods and Results

During the 2022 dengue season, we enrolled 384 patients presenting at a hospital in Kathmandu with dengue-like symptoms; 79% of the study participants had active or recent DENV infection (NS1 antigen and IgM). To identify circulating serotypes, we screened serum from 50 of the NS1 + participants by RT-PCR and identified DENV1, 2, and 3 - with DENV1 and 3 codominant. We also performed whole-genome sequencing of DENV, for the first time in Nepal, using our new on-site capacity. Sequencing analysis demonstrated the DENV1 and 3 genomes clustered with sequences reported from India in 2019, and the DENV2 genome clustered with a sequence reported from China in 2018.

Conclusion

These findings highlight DENV's geographic expansion from neighboring countries, identify China and India as the likely origin of the 2022 DENV cases in Nepal, and demonstrate the feasibility of building onsite capacity for more rapid genomic surveillance of circulating DENV. These ongoing efforts promise to protect populations in Nepal and beyond by informing the development and deployment of DENV drugs and vaccines in real time.

Indian Ocean temperature anomalies predict long-term global dengue trends

Despite identifying El Niño events as a factor in dengue dynamics, predicting the oscillation of global dengue epidemics remains challenging. Here, we investigate climate indicators and worldwide dengue incidence from 1990 to 2019 using climate-driven mechanistic models. We identify a distinct indicator, the Indian Ocean basin-wide (IOBW) index, as representing the regional average of sea surface temperature anomalies in the tropical Indian Ocean. IOBW is closely associated with dengue epidemics for both the Northern and Southern hemispheres. The ability of IOBW to predict dengue incidence likely arises as a result of its effect on local temperature anomalies through teleconnections. These findings indicate that the IOBW index can potentially enhance the lead time for dengue forecasts, leading to better-planned and more impactful outbreak responses.

Severe dengue infection unmasking drug-induced liver injury: Successful management with N-acetylcysteine

Key Clinical Message

Clinicians in tuberculosis and dengue endemic regions should have heightened vigilance for drug-induced liver injury (DILI) overlapping with active infections, enabling prompt recognition and life-saving conservative management.

Abstract

Severe dengue and drug-induced liver injury (DILI) are significant independent risk factors for acute liver failure. The co-occurrence of these conditions significantly complicates clinical management. Here, we describe the case of a 21-year-old Nepali female who developed acute liver failure during antitubercular therapy (ATT). The patient, presenting with fever and nausea after 3 weeks of ATT, subsequently received a diagnosis of severe dengue. Laboratory evidence indicated markedly elevated transaminases (AST 4335 U/L, ALT 1958 U/L), total bilirubin (72 μmol/L), and INR (>5). Prompt discontinuation of first-line ATT, initiation of a modified ATT regimen, and N-acetylcysteine (NAC) infusion facilitated the patient's recovery after a week of intensive care. This case underscores the potential for synergistic hepatotoxicity in regions where multiple endemic illnesses coincide. Early recognition of DILI, cessation of offending agents, and comprehensive intensive care are crucial interventions. While the definitive efficacy of NAC remains under investigation, its timely administration in these complex cases warrants exploration for its potential lifesaving benefits.

The dengue-specific immune response and antibody identification with machine learning

Dengue virus poses a serious threat to global health and there is no specific therapeutic for it. Broadly neutralizing antibodies recognizing all serotypes may be an effective treatment. High-throughput adaptive immune receptor repertoire sequencing (AIRR-seq) and bioinformatic analysis enable in-depth understanding of the B-cell immune response. Here, we investigate the dengue antibody response with these technologies and apply machine learning to identify rare and underrepresented broadly neutralizing antibody sequences. Dengue immunization elicited the following signatures on the antibody repertoire: (i) an increase of CDR3 and germline gene diversity; (ii) a change in the antibody repertoire architecture by eliciting power-law network distributions and CDR3 enrichment in polar amino acids; (iii) an increase in the expression of JNK/Fos transcription factors and ribosomal proteins. Furthermore, we demonstrate the applicability of computational methods and machine learning to AIRR-seq datasets for neutralizing antibody candidate sequence identification. Antibody expression and functional assays have validated the obtained results.

Interactions between climate change, urban infrastructure and mobility are driving dengue emergence in Vietnam

Dengue is expanding globally, but how dengue emergence is shaped locally by interactions between climatic and socio-environmental factors is not well understood. Here, we investigate the drivers of dengue incidence and emergence in Vietnam, through analysing 23 years of district-level case data spanning a period of significant socioeconomic change (1998-2020). We show that urban infrastructure factors (sanitation, water supply, long-term urban growth) predict local spatial patterns of dengue incidence, while human mobility is a more influential driver in subtropical northern regions than the endemic south. Temperature is the dominant factor shaping dengue's distribution and dynamics, and using long-term reanalysis temperature data we show that warming since 1950 has expanded transmission risk throughout Vietnam, and most strongly in current dengue emergence hotspots (e.g., southern central regions, Ha Noi). In contrast, effects of hydrometeorology are complex, multi-scalar and dependent on local context: risk increases under either short-term precipitation excess or long-term drought, but improvements in water supply mitigate drought-associated risks except under extreme conditions. Our findings challenge the assumption that dengue is an urban disease, instead suggesting that incidence peaks in transitional landscapes with intermediate infrastructure provision, and provide evidence that interactions between recent climate change and mobility are contributing to dengue's expansion throughout Vietnam.

D. R, Lakshmi M. I, Isvaran K, Ghosh SK, Ishtiaq F. Determinants of Aedes mosquito larval ecology in a heterogeneous urban environment- a longitudinal study in Bengaluru, India

BACKGROUND

Aedes-borne disease risk is associated with contemporary urbanization practices where city developing structures function as a catalyst for creating mosquito breeding habitats. We lack better understanding on how the links between landscape ecology and urban geography contribute to the prevalence and abundance of mosquito and pathogen spread.

METHODS

An outdoor longitudinal study in Bengaluru (Karnataka, India) was conducted between February 2021 and June 2022 to examine the effects of macrohabitat types on the diversity and distribution of larval habitats, mosquito species composition, and body size to quantify the risk of dengue outbreak in the landscape context.

FINDINGS

A total of 8,717 container breeding sites were inspected, of these 1,316 were wet breeding habitats. A total of 1,619 mosquito larvae representing 16 species from six macrohabitats and nine microhabitats were collected. Aedes aegypti and Aedes albopictus were the dominant species and significantly higher in artificial habitats than in natural habitats. Breeding preference ratio for Aedes species was high in grinding stones and storage containers. The Aedes infestation indices were higher than the WHO threshold and showed significant linear increase from Barren habitat to High density areas. We found Ae. albopictus breeding in sympatry with Ae. aegypti had shorter wing length.

CONCLUSIONS

A large proportion of larval habitats were man-made artificial containers. Landscape ecology drives mosquito diversity and abundance even at a small spatial scale which could be affecting the localized outbreaks. Our findings showed that sampling strategies for mosquito surveillance must include urban environments with non-residential locations and dengue transmission reduction programmes should focus on 'neighbourhood surveillance' as well to prevent and control the rising threat of Aedes-borne diseases.

Sociodemographic factors associated to knowledge and attitudes towards dengue prevention among the Peruvian population: findings from a national survey

OBJECTIVES

To evaluate the frequency of knowledge and attitudes towards dengue prevention among the Peruvian population, as well as the sociodemographic factors associated with reported knowledge and attitude outcomes.

DESIGN/SETTING

A cross-sectional study was conducted, based on information from the National Survey of Budget Programs of Peru, 2019.

PARTICIPANTS

We included 57 829 respondents with a mean age of 40.3±17.4 years, of whom 52.8% were women and 87.6% were from urban areas.

PRIMARY AND SECONDARY OUTCOMES

Knowledge about dengue infection (transmission, symptoms, importance of going to a health centre and not self-medicating) and preventive attitudes to avoid infection.

RESULTS

Of all the respondents, 36.2% (n=23 247) presented good knowledge about dengue and 11.6% (n=7890) had a higher number of preventive attitudes (≥3 attitudes). In the multivariate regression analysis, we found that being female (for knowledge: aPR (adjusted prevalence ratio): 1.03; 95% CI 1.02 to 1.03; and for attitude: aPR: 1.02; 95% CI 1.01 to 1.02), being married/cohabiting (for knowledge: aPR: 1.02; 95% CI 1.00 to 1.03; and for attitude: aPR: 1.01; 95% CI 1.00 to 1.02) and residing in the jungle (for knowledge: aPR: 1.14; 95% CI 1.12 to 1.16; and for attitude: aPR: 1.09; 95% CI 1.07 to 1.11) were associated with better knowledge and more preventive attitudes. In addition, we found that being an adolescent (for knowledge: aPR: 0.97; 95% CI 0.96 to 0.99; and for attitude: aPR: 0.99; 95% CI 0.97 to 0.99), and belonging to the Quechua ethnic group (for knowledge: aPR: 0.93; 95% CI 0.91 to 0.94; and for attitude: aPR: 0.98; 95% CI 0.97 to 0.99) were associated with a lower proportion of adequate knowledge and fewer preventive attitudes.

CONCLUSIONS

Our study found a high proportion of poor knowledge and few preventive attitudes towards dengue in the Peruvian population. That highlights the requirement to implement national strategies to educate people about dengue and promote preventive attitudes, considering the factors found.

Climate Change and Travel: Harmonizing to Abate Impact

Purpose of Review

With climate change being the single biggest health threat facing humanity, this review aims to identify the climate-sensitive health risks to the traveler and to recognize the role that travel plays in contributing to the detrimental effects of climate change. With this understanding, adaptations for transformational action can be made.

Recent Findings

Travel and tourism, including transportation, food consumption, and accommodation, is responsible for a large percentage of the world’s carbon emissions which is contributing to the climate change crisis at an alarming rate. Climate change is a health emergency that is resulting in a rise of significant health impacts to the traveler including increased heat illnesses; food-, water-, and vector-borne diseases; and increasing risk of exposure to emerging infectious diseases. Patterns of future travel and destination choices are likely to change due to climactic factors such as temperature and extreme weather events, forced migration, degradation, and disappearance of popular and natural tourist destinations.

Summary

Global warming is and will continue to alter the landscape of travel medicine with expansion of transmission seasons and geographic ranges of disease, increased risk of infections and harmful marine toxins, and introduction of emerging infections to naïve populations. This will have implications for pre-travel counseling in assessing risk and discussing the environmental influences on travel. Travelers and stakeholders should be engaged in a dialogue to understand their “climate footprint,” to innovate sustainable solutions, and be empowered to make immediate, conscientious, and responsible choices to abate the impact of breaching critical temperature thresholds.

Perceptions around COVID-19 and vaccine hesitancy: A qualitative study in Kaski district, Western Nepal

Burgeoning morbidity and mortality due to COVID-19 pandemic including the peaks in outbreaks due to different variants have attracted global attention. Although the development and rolling out of vaccines have been impressive, low- and middle-income countries suffer from a double burden: (1) lack of adequate vaccines; and (2) low vaccine uptake (vaccine hesitancy). The main objective of this study was to explore perceptions around COVID-19 and vaccine hesitancy among urban and rural population in Western Nepal. A qualitative study was conducted in six urban wards of Pokhara municipality and four rural municipalities in Kaski district of Nepal. A semi-structured interview guide was used to interview participants who were selected purposively to explore the perceived burden of COVID-19 pandemic, roles, and contributions of vaccine. Nineteen interviews were conducted by telephone following a government recommendation to avoid face-to-face meetings. Audio-recorded interviews were thematically analysed after transcription and translation into English. COVID-19 is a major (public) health concern and affects people at an individual, societal and national level. People dreaded its health hazards and consequences and seemed to be compliant with public health measures such as maintaining social distance, wearing masks and maintaining hygiene. Vaccine was considered to be a major intervention to fight the pandemic, nonetheless, the rationale and benefits of vaccines were blemished by the perceived lack of the vaccine's effectiveness, duration of protection, and its potential side-events. Expedited development of vaccine was embraced with suspicion that vaccine may have incurred compromise in quality. Science and rationale behind vaccine were smeared by misinformation and clearly counteracting the misinformation were deemed critical. Providing information about vaccines through government entities (who are trusted) and respected individuals may engender trust and uptake of vaccine. Fighting off misinformation of COVID-19 is critical to curb the course of pandemic. Increased attention towards monitoring and investing in legitimacy of information and offering information through trusted sources can help improve the vaccine coverage.

Rapid range shifts in African Anopheles mosquitoes over the last century

Facing a warming climate, many tropical species-including the arthropod vectors of several infectious diseases-will be displaced to higher latitudes and elevations. These shifts are frequently projected for the future, but rarely documented in the present day. Here, we use one of the most comprehensive datasets ever compiled by medical entomologists to track the observed range limits of African malaria mosquito vectors (Anopheles spp.) from 1898 to 2016. Using a simple regression approach, we estimate that these species' ranges gained an average of 6.5 m of elevation per year, and the southern limits of their ranges moved polewards 4.7 km per year. These shifts would be consistent with the local velocity of recent climate change, and might help explain the incursion of malaria transmission into new areas over the past few decades. Confirming that climate change underlies these shifts, and applying similar methods to other disease vectors, are important directions for future research.

Factors influencing the knowledge, attitude, and practices of police personnel toward dengue fever in Kathmandu, Nepal

OBJECTIVE

Dengue fever is a significant public health problem in Nepal, and police personnel are considered to play a crucial role in preventing and controlling dengue fever. This study aimed to assess the factors that influence the knowledge, attitudes, and practices of police personnel toward dengue in Kathmandu, Nepal.

METHODS

The study design was a descriptive cross-sectional study among 422 police personnel, where data were collected using self-administered questionnaires. Bi-variate analysis and multivariate analysis were used to examine the association between sociodemographic factors and environmental factors with knowledge, attitude, and practices of dengue.

RESULTS

The study found that the knowledge, attitude, and practice toward dengue prevention was 58%, 46%, and 75%, respectively. The study found that family history of dengue (AOR = 2.78, 95% CI = 1.38-5.6), owning bed nets (AOR = 2.13, 95% CI = 1.04-4.35) and having covered water storage containers (AOR = 2.99, 95% CI = 1.74-5.13) were associated with higher odds of knowledge on dengue. Having family history of dengue (AOR = 2.45, 95% CI = 1.24-4.87) and the presence of broken glasses or discarded plastic bottles in the house (AOR = 2.07, 95% CI = 1.93-5.36) were associated with attitude on dengue. Knowledge on dengue was associated with higher odds of attitude (AOR = 3.3, 95% CI = 2.09-5.36) and practices (AOR = 3.21, 95% CI = 1.93, 5.36).

CONCLUSION

The study identified specific factors associated with knowledge, attitude, and practices toward dengue prevention. The study concluded that regular training and awareness-raising activities are needed to improve their knowledge, attitudes, and practices toward dengue.

Dengue Dilemma in Nepal

The first case of Dengue in Nepal  was reported in 2004, after a traveller returned from India. Dengue has since then been an endemic disease within the country with all 4 serotypes (DENV-1,DENV-2,DENV-3 and DENV-4) being known to exist and circulate within the region. Based on epidemiological records the DENV-1 and DENV-2 serotypes have traditionally been the most incriminated serovars in terms of national disease burden according to the Epidemiology and the disease control division (EDCD). Since the beginning of January 2022 up until the 28th of September 2022 over 28000 cases of confirmed and suspected cases of dengue fever have been reported to the WHO with a total of 38 deaths being documented across all of Nepal’s provinces. To date the predominant implicated serotype or serotypes have not been identified. The province most adversely affected is the Bagmati province which accounts for 78.2% of the cases and 68.4% of the fatalities noted in Nepal. A further rise in cases has been noted as of the 8th of August 2022. This dengue outbreak is the largest recorded outbreak within the small mountainous regions recent history. The latest data released by the Ministry of health and population of Nepal (11th December 2022), has recorded a total of 54232 cases with the Bagmati province accounting for 42143 thereof and Lumbini province 4984 respectively. To date a total of 67 deaths have been confirmed. The top 10 reporting districts are namely: 1.Kathmandu (14165) 2.Lalitpur (9614) 3.Bhaktapur(6145) 4.Mawkanpur (5830) 5.Chitawan (3188) 6.Dang (2405) 7. Dhading(1678) 8. Rupandehi (1203) 9. Kavrepalanchok (536) and 10. Surkhet (470) cases respectively. Due to the treatment of the disease being predominantly supportive, the prevention of the spread through enhanced and improved vector control and elimination is recommended. The use of eradication programs, impregnated mosquito nets, larvicidal and chromosomal manipulation therapies are the most effective methods to aid and abet the control of this deadly virus. The coming months and response of the spread of the virus to the intimated control programs implemented in Nepal will act as a yardstick for the future development and course of the outbreak of Dengue within the mountainous region.

Epidemiology of dengue in SAARC territory: a systematic review and meta-analysis

BACKGROUND

Dengue is one of the common arboviral infections and is a public health problem in South East Asia. The aim of this systematic review and meta-analysis was to evaluate the prevalence and distribution of dengue in SAARC (South Asian Association for Regional Cooperation) countries.

METHODS

The PubMed, PubMed Central, Embase and Scopus databases were searched for relevant studies. Statistical analysis on data extracted from the selected studied was conducted using the Comprehensive Meta-Analysis Software (CMA) version 3 software package. Proportions were used to estimate the outcome with a 95% confidence interval (CI).

RESULTS

Across all studies, among cases of suspected dengue, 30.7% were confirmed dengue cases (proportion: 0.307, 95% CI: 0.277-0.339). The seroprevalence of dengue immunoglobulin (Ig)G, IgM or both (IgM and IgG) antibodies and dengue NS1 antigen was 34.6, 34.2, 29.0 and 24.1%, respectively. Among the different strains of dengue, dengue virus (DENV) strains DENV-1, DENV-2, DENV-3 and DENV-4 accounted for 21.8, 41.2, 14.7 and 6.3% of cases, respectively. The prevalence of dengue fever, dengue hemorrhagic fever and dengue shock syndrome was 80.5, 18.2 and 1.5%, respectively. Fever was a commonly reported symptom, and thrombocytopenia was present in 44.7% of cases. Mortality was reported in 1.9% of dengue cases.

CONCLUSIONS

Dengue is a common health problem in South East Asia with high seroprevalence. DENV-2 was found to be the most common strain causing infection, and most dengue cases were dengue fever. In addition, thrombocytopenia was reported in almost half of the dengue cases.

ArVirInd-a database of arboviral antigenic proteins from the Indian subcontinent

Background

Studies on antigenic proteins for arboviruses are important for providing diagnostics and vaccine development. India and its neighboring countries have a huge burden of arboviral diseases. Data mining for country-specific sequences from existing bioinformatics databases is cumbersome and time-consuming. This necessitated the development of a database of antigenic proteins from arboviruses isolated from the countries of the Indian subcontinent.

Methods

Arboviral antigenic protein sequences were obtained from the NCBI and other databases. In silico antigenic characterization was performed (Epitope predictions) and data was incorporated into the database. The front end was designed and developed using HTML, CSS, and PHP. For the backend of the database, we have used MySQL.

Results

A database, named ArVirInd, is created as a repository of information on curated antigenic proteins. This enlists sequences by country and year of outbreak or origin of the viral strain. For each entry, antigenic information is provided along with functional sites, etc. Researchers can search this database by virus/protein name, country, and year of collection (or in combination) as well as peptide search for epitopes. It is available publicly via the Internet at http://www.arvirind.co.in. ArVirInd will be useful in the study of immune informatics, diagnostics, and vaccinology for arboviruses.

Dengue encephalitis featuring “double-doughnut” sign - A case report

Introduction

Dengue is a common febrile illness caused by Dengue virus and spread by Aedes mosquitoes. The neurological complications like encephalopathy or encephalitis or immune-mediated neurological syndromes are uncommon though. Discrete neuroimaging findings in this setting are even rarer. We report a case of dengue encephalitis with uncommon MRI features in a young female.

Case presentation

The patient presented with complains of fever, vomiting, weakness in all limbs and difficulty in speech. Neurological examination revealed bilateral horizontal gaze palsy with impaired oculo-cephalic reflex, bulbar dysarthria and quadriplegia with bilateral planters up-going. Laboratory reported anemia, thrombocytopenia and positive NS1 antigen while excluding other tropical and immunological diseases. Brain MRI revealed extensive thalamic involvement as unique “double-doughnut” sign along with lesions in brainstem. The patient received supportive treatment in intensive unit and was discharged following improvement in clinical condition and laboratory reports.

Clinical discussion

Dengue can infect the central nervous system directly as encephalitis or can have neurological consequences following multi-organ dysfunction and shock as encephalopathy or post-infection immunological syndromes as Guillain-Barré Syndrome or cerebrovascular complications or dengue muscle dysfunction. The MRI appearance of “double-doughnut” sign points towards dengue encephalitis in appropriate setting.

Conclusion

A high index of suspicion is required to make a diagnosis of dengue encephalitis. The “double-doughnut” sign in MRI sequences has the potential to become a diagnostic marker for dengue encephalitis.

•

Dengue encephalitis is an uncommon complication of dengue infection.

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The extensive lesions and unique “double-doughnut” sign in MRI are even rarer.

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The sign has a potential to become a diagnostic marker in an appropriate setting.

Aedes albopictus abundance and phenology along an altitudinal gradient in Lazio region (central Italy)

Background

The Asian tiger mosquito Aedes albopictus (Skuse 1894), which is native to Southeast Asia, is among the top 100 invasive species worldwide and one of the most troubling vector species. It has become established in more than 20 European countries. Since its arrival in Italy in the 1990s, the species has colonized all the regions of the country, up to an altitude of 600 m. Nevertheless, no thorough investigation has ever been performed to confirm or extend its elevation limit (EL) in Italy.

Methods

To define the EL of Ae. albopictus and analyse its phenology along an altitudinal gradient, we carried out an investigation by means of ovitraps placed in Lazio region, central Italy. Sampling was performed on a weekly basis in 13 villages within five 200-m altitudinal ranges [0–1000 m above sea level (asl)], with the addition of higher localities to the species range whenever the species was recorded in the highest range.

Results

Aedes albopictus has colonized sites well beyond its known EL, with established populations at 900 m asl and positive ovitraps recorded at 1193 m asl. The relationship between egg abundance and elevation was described by an exponential decay regression, which predicted an EL for oviposition at 1015 m asl. In the active season, egg-laying started earlier at low altitude and ended earlier within the highest altitudinal range. Aedes albopictus abundance and activity period (number of days active) decreased, respectively, by 95% and 34% from the lowest to the highest altitudinal range.

Conclusions

Using data from the present study, the altitudinal limit of Ae. albopictus in central Italy was updated from 600 to 900 m asl. In addition, established populations were predicted to exist up to 1015 m asl. Considering that up to 99.5% of Lazio region’s inhabitants could potentially be affected by Aedes-borne virus outbreaks, the surveillance area for Ae. albopictus should be expanded accordingly. However, our results also indicate that Ae. albopictus surveillance programs need to be revised in order to harmonize the resources earmarked for these with the altitudinal changes in the phenology of this species.

Graphical abstract

Integrated view of molecular diagnosis and prognosis of dengue viral infection: future prospect of exosomes biomarkers

Dengue viruses (DENVs) are the viruses responsible for dengue infection which affects lungs, liver, heart and also other organs of individuals. DENVs consist of the group of four serotypically diverse dengue viruses transmitted in tropical and sub-tropical countries of world. Aedes mosquito is the principal vector which spread the infection from infected person to healthy humans. DENVs can cause different syndromes depending on serotype of virus which range from undifferentiated mild fever to dengue hemorrhagic fever resulting in vascular leakage due to release of cytokine and Dengue shock syndrome with fluid loss and hypotensive shock, or other severe manifestations such as bleeding and organ failure. Increase in dengue cases in pediatric population is a major concern. Transmission of dengue depends on various factors like temperature, rainfall, and distribution of Aedes aegypti mosquitoes. The present review describes a comprehensive overview of dengue, pathophysiology, diagnosis, treatment with an emphasis on potential of exosomes as biomarkers for early prediction of dengue in pediatrics.

Dengue and scrub typhus co-infection causing septic shock

A 33-year-old female presented with a history of high-grade fever, cough, dyspnea, joint pain and myalgia. On examination, the patient was febrile with tachycardia, hypotension and decreased oxygen saturation. Chest auscultation revealed bilateral decreased air entry with crepitation supported by bilateral pulmonary infiltrates on chest X-ray. The laboratory investigations showed leukocytosis, thrombocytopenia, transaminitis and renal impairment. The patient was treated with intravenous fluids, ceftriaxone and levofloxacin; however, there was no clinical improvement till 48 h. She was then diagnosed with scrub typhus and dengue co-infection via serologies. Doxycycline was started following which the patient improved in 24 h. Scrub typhus can present with septic shock but does not respond to the usual antibiotics and the addition of doxycycline will result in rapid clinical improvement. Co-infection with other tropical diseases such as dengue is also common, hence it is important to test based on local endemicity.

Seroprevalence and Clinical Features of Scrub Typhus among Febrile Patients Attending a Referral Hospital in Kathmandu, Nepal

(1) Background: Scrub typhus (ST) is endemic to Nepal. It is often underdiagnosed and misdiagnosed due to non-specific clinical presentation coupled with limited microbiological facilities, leading to adverse clinical outcomes. This study aimed to assess the seroprevalence of scrub typhus in febrile patients attending Sukraraj Tropical and Infectious Disease Hospital (STIDH), Nepal, from August 2018 to April 2019. (2) Materials and Method: Blood/serum samples and clinical and demographic data of adult febrile patients (≥19 years) who attended or were referred to the hospital were collected after obtaining written informed consent from the participants excluding immunocompromised individuals. Collected blood/serum samples were subjected to hematological, biochemical, and serological tests. A serological test for scrub typhus was performed using the ImmuneMed scrub typhus rapid diagnostic test kit. Data generated were analyzed using SPSS software version 24.0. (3) Results: Amongst the 2070 febrile patients, 462 (22.3%) were seropositive to at least one etiological agent of febrile illnesses (scrub typhus: 253 cases, dengue: 101 cases, leptospirosis: 9, brucellosis: 52, malaria: 9 and kala-azar: 20 cases). Scrub typhus accounted for 12.2% (n = 253) of total febrile illnesses followed by dengue (4.9%, n = 101). Mixed seropositivity of scrub typhus with dengue, brucellosis, and typhoid was found in 12 (0.6%), 9 (0.4%), and 5 (0.2%) cases, respectively. Among 253 scrub typhus patients, 53.4% were female. Among the 154 patients, the most common symptoms were fever (100%), headache (79.2%), sweating (70.1%), breathing difficulty (51.3%), redness of the eye (43.5%), and pathognomonic eschar was observed in 9.1% patients. Fifty percent of scrub typhus patients had low platelet count and >30% of patients had an elevated level of liver enzymes (such as serum glutamic oxaloacetic transaminase (SGPT) and serum glutamic pyruvic transaminase (SGOT). (4) Conclusion: Scrub typhus is a considerable cause of febrile illness in Nepal. Females apparently have a higher chance of acquiring scrub typhus. ST presents nonspecific clinical presentation. The diagnostic dilemma of typhus patients can be minimized by the early monitoring of ST-associated symptoms. The country's health system needs to be strengthened for early outbreak detection, and immediate response actions against scrub typhus to control the future outbreak of ST.