Molecular and Entomological Characterization of 2023 Dengue Outbreak in Dhading District, Central Nepal

In 2023, Nepal faced its second largest dengue outbreak ever, following a record-breaking number of dengue cases in 2022, characterized by the expansion of infections into areas of higher altitudes. However, the characteristics of the 2023 circulating dengue virus (DENV) and the vector density remain poorly understood. Therefore, we performed DENV serotyping, clinical and laboratory assessment, and entomological analysis of the 2023 outbreak in central Nepal. A total of 396 fever cases in Dhading hospital suspected of being DENV positive were enrolled, and blood samples were collected and tested by different techniques including PCR. Of these, 278 (70.2%) had confirmed DENV infection. Multiple serotypes (DENV-1, -2, and -3) were detected. DENV-2 (97.5%) re-emerged after six years in Dhading while DENV-3 was identified for the first time. Dengue inpatients had significantly higher frequency of anorexia, myalgia, rash, diarrhea, nausea, vomiting, abdominal pain, and thrombocytopenia (p < 0.05). In this area, Aedes mosquitoes largely predominated (90.7%) with the majority being A. aegypti (60.7%). We also found high levels of Aedes index (20.0%) and container index (16.7%). We confirmed multiple DENV serotype circulation with serotype re-emergence and new serotype introduction, and high vector density in 2023. These findings call for the urgent initiation and scaling up of DENV molecular surveillance in human and mosquito populations for dengue control and prevention in Nepal.

Phylogenetic Investigations of Dengue 2019-2021 Outbreak in Guadeloupe and Martinique Caribbean Islands

Dengue fever has been a public health problem in the Caribbean region since 1981, when it first reappeared in Cuba. In 1989, it was reported in Martinique and Guadeloupe (two French islands 200 km apart); since then, DENV has caused several epidemics locally. In 2019-2021, DENV-1, DENV-2, and DENV-3 were detected. Serotype distribution was differentiated, with DENV-2 and DENV-3 predominating in Guadeloupe and Martinique, respectively. Complete genome sequencing was carried out on 32 specimens, and phylogenic analysis identified the circulation of genotype V for DENV-1, cosmopolitan genotype for DENV-2, and genotype III for DENV-3. However, two distinct circulating groups were identified for DENV-1 and DENV-3, suggesting independent introductions. Overall, despite the context of the COVID-19 pandemic and the associated travel restrictions, these results confirm the active circulation of DENV and specific epidemiological features on each of the two islands. Such differences may be linked to the founder effect of the various introduction events, and to local factors such as the population immunity and the transmission capacity of the vectors. Further genomic and epidemiological characterization of DENV strains remains essential to understand how dengue spreads in each specific geographical context and to prevent future epidemics.

Recent Dengue Infection in Bangladesh: A Seasonal Endemic Progressing to Year-long Serious Health Concern

Dengue represents one of the most dangerous mosquito-borne viral diseases. Although the disease has been prevalent around the globe over the centuries, recent outbreaks of dengue have devasted the healthcare delivery system of many countries. Being a global infection, dengue virus (DENV) is endemically present mainly in Latin America and Caribbean countries as well as countries in South Asia. The recent outbreak of DENV infection has indicated an exceptional outbreak of DENV in some countries in South Asia. There has been a serious endemic of DENV during 2019. After a heterogeneous pause, another severe outbreak of DENV was reported in some Asian countries in 2023. Among the Asian countries, Bangladesh has reported an acute upsurge of DENV infection in 2023 with record numbers of fatalities. However, this pattern of DENV has not been detected in neighbors of Bangladesh, such as India or other countries in Southeast Asia. This provides an emergent task of dissecting the present DENV infection in Bangladesh from different angles to get insights for future containment of the DENV infection, not only in Bangladesh but also in other DENV endemic areas or DENV-native areas.

How to cite this article

Akbar SMF, Khan S, Mahtab M, et al. Recent Dengue Infection in Bangladesh: A Seasonal Endemic Progressing to Year-long Serious Health Concern. Euroasian J Hepato-Gastroenterol 2023;13(2):145-151.

Associated risk factors of severe dengue in Reunion Island: A prospective cohort study

BACKGROUND

Since 2018, a dengue epidemic has been raging annually in Reunion Island, which poses the major problem of its morbidity and mortality. However, there is no consensus in the literature on factors associated with severity of illness. The objective of this study was to identify the factors associated with the occurrence of severe dengue (SD) according to the criteria adopted in 2009 by the World Health Organization (WHO), during the 2019 epidemic.

METHODOLOGY/PRINCIPAL FINDINGS

A total of 163 patients with RT-PCR-confirmed dengue were included in a multicenter prospective cohort study in Reunion Island between January and June 2019. Of these, 37 (23%) were classified as SD, which involves presentation dominated by at least one organ failure, and 126 (77%) classified as non-SD (of which 90 (71%) had warning signs). Confusion, dehydration, and relative hypovolemia were significantly associated with SD in bivariate analysis (p < 0.05). The factors associated with SD in multivariate analysis were a time from first symptom to hospital consultation over 2 days (OR: 2.46, CI: 1.42-4.27), a history of cardiovascular disease (OR: 2.75, 95%CI: 1.57-4.80) and being of Western European origin (OR: 17.60, CI: 4.15-74).

CONCLUSIONS/SIGNIFICANCE

This study confirms that SD is a frequent cause of hospitalization during dengue epidemics in Reunion Island. It suggests that cardiovascular disease, Western European origin, and delay in diagnosis and management are risk factors associated with SD fever, and that restoration of blood volume and correction of dehydration must be performed early to be effective.

TRIAL REGISTRATION

NCT01099852; clinicaltrials.gov.

Dengue Fever in Italy: The "Eternal Return" of an Emerging Arboviral Disease

Enhanced surveillance for dengue virus (DENV) infections in Italy has been implemented since 2012, with annual reports from the National Health Institute. In this study, we summarize available evidence on the epidemiology of officially notified DENV infections from 2010–2021. In total, 1043 DENV infection cases were diagnosed, and most of them occurred in travelers, with only 11 autochthonous cases. The annual incidence rates of DENV infections peaked during 2019 with 0.277 cases per 100,000 (95% confidence interval [95% CI] 0.187–0.267), (age-adjusted incidence rate: 0.328, 95% CI 0.314–0.314). Cases of DENV were clustered during the summer months of July (11.4%), August (19.3%), and September (12.7%). The areas characterized by higher notification rates were north-western (29.0%), and mostly north-eastern Italy (41.3%). The risk for DENV infection in travelers increased in the time period 2015–2019 (risk ratio [RR] 1.808, 95% CI 1.594–2.051) and even during 2020–2021 (RR 1.771, 95% CI 1.238–2.543). Higher risk for DENV was additionally reported in male subjects compared with females subjects, and aged 25 to 44 years, and in individuals from northern and central Italy compared to southern regions and islands. In a multivariable Poisson regression model, the increased number of travelers per 100 inhabitants (incidence rate ratio [IRR] 1.065, 95% CI 1.036–1.096), the incidence in other countries (IRR 1.323, 95% CI 1.165–1.481), the share of individuals aged 25 to 44 years (IRR 1.622, 95% CI 1.338–1.968), and foreign-born residents (IRR 2.717, 95% CI 1.555–3.881), were identified as effectors of annual incidence. In summary, although the circulation of DENV remains clustered among travelers, enhanced surveillance is vital for the early detection of human cases and the prompt implementation of response measures.

Genetic lineage characterization and spatiotemporal dynamics of classical insect-specific flaviviruses: outcomes and limitations

The genus Flavivirus incorporates bona fide arboviruses, as well as others viruses with restricted replication in insect cells. Among the latter, a large monophyletic cluster of viruses, known as cISF (classical insect-specific flaviviruses), has been sampled in many species of mosquitoes collected over a large geographic range. In this study, we investigated nucleotide and protein sequences with a suite of molecular characterization approaches including genetic distance, Shannon entropy, selective pressure analysis, polymorphism identification, principal coordinate analysis, likelihood mapping, phylodynamic reconstruction, and spatiotemporal dispersal, to further characterize this diverse group of insect-viruses. The different lineages and sub-lineages of viral sequences presented low sequence diversity and entropy (though some displayed lineage-specific polymorphisms), did not show evidence of frequent recombination and evolved under strong purifying selection. Moreover, the reconstruction of the evolutionary history and spatiotemporal dispersal was highly impacted by overall low signals of sequence divergence throughout time but suggested that cISF distribution in space and time is dynamic and may be dependent on human activities, including commercial trading and traveling.

The dengue preface to endemic in mainland China: the historical largest outbreak by Aedes albopictus in Guangzhou, 2014

Background

Dengue was regarded as a mild epidemic in mainland China transmitted by Aedes albopictus. However, the 2014 record-breaking outbreak in Guangzhou could change the situation. In order to provide an early warning of epidemic trends and provide evidence for prevention and control strategies, we seek to characterize the 2014 outbreak through application of detailed cases and entomological data, as well as phylogenetic analysis of viral envelope (E) gene.

Methods

We used case survey data identified through the Notifiable Infectious Disease Report System, entomological surveillance and population serosurvey, along with laboratory testing for IgM/IgG, NS1, and isolation of viral samples followed by E gene sequencing and phylogenetic analysis to examine the epidemiological and molecular characteristics of the outbreak.

Results

The 2014 dengue outbreak in Guangzhou accounted for nearly 80% of total reported cases that year in mainland China; a total of 37,376 cases including 37,340 indigenous cases with incidence rate 2908.3 per million and 36 imported cases were reported in Guangzhou, with 14,055 hospitalized and 5 deaths. The epidemic lasted for 193 days from June 11 to December 21, with the highest incidence observed in domestic workers, the unemployed and retirees. The inapparent infection rate was 18.00% (135/750). In total, 96 dengue virus 1 (DENV-1) and 11 dengue virus 2 (DENV-2) strains were isolated. Phylogenetic analysis indicated that the DENV-1 strains were divided into genotype I and V, similar to the strains isolated in Guangzhou and Dongguan in 2013. The DENV-2 strains isolated were similar to those imported from Thailand on May 11 in 2014 and that imported from Indonesia in 2012.

Conclusions

The 2014 dengue epidemic was confirmed to be the first co-circulation of DENV-1 and DENV-2 in Guangzhou. The DENV-1 strain was endemic, while the DENV-2 strain was imported, being efficiently transmitted by the Aedes albopictus vector species at levels as high as Aedes aegypti.

Electronic supplementary material

The online version of this article (doi:10.1186/s40249-017-0352-9) contains supplementary material, which is available to authorized users.

Google dengue trends: An indicator of epidemic behavior. The Venezuelan Case

INTRODUCTION

Dengue Fever is a neglected increasing public health thread. Developing countries are facing surveillance system problems like delay and data loss. Lately, the access and the availability of health-related information on the internet have changed what people seek on the web. In 2004 Google developed Google Dengue Trends (GDT) based on the number of search terms related with the disease in a determined time and place. The goal of this review is to evaluate the accuracy of GDT in comparison with traditional surveillance systems in Venezuela.

METHODS

Weekly epidemic data from GDT, Official Reported Cases (ORC) and Expected Cases (EC) according the Ministry of Health (MH) was obtained Monthly and yearly correlation between GDT and ORC from 2004 until 2014 was obtained. Linear regressions taking the reported cases as dependent variable were calculated.

RESULTS

The overall Pearson correlation between GDT and ORC was r=0.87 (p <0.001), while between ORC and EC according the Ministry of Health (MH) was r=0.33 (p<0.001). After clustering data in epidemic and non-epidemic weeks in comparison with GDT correlation were r=0.86 (p<0.001) and r=0.65 (p <0.001) respectively. Important interannual variation of the epidemic was observed. The model shows a high accuracy in comparison with the EC, particularly when the incidence of the disease is higher.

CONCLUSIONS

This early warning tool can be used as an indicator for other communicable diseases in order to apply effective and timely public health measures especially in the setting of weak surveillance systems.

Clustering, climate and dengue transmission

Dengue is currently the most rapidly spreading vector-borne disease, with an increasing burden over recent decades. Currently, neither a licensed vaccine nor an effective anti-viral therapy is available, and treatment largely remains supportive. Current vector control strategies to prevent and reduce dengue transmission are neither efficient nor sustainable as long-term interventions. Increased globalization and climate change have been reported to influence dengue transmission. In this article, we reviewed the non-climatic and climatic risk factors which facilitate dengue transmission. Sustainable and effective interventions to reduce the increasing threat from dengue would require the integration of these risk factors into current and future prevention strategies, including dengue vaccination, as well as the continuous support and commitment from the political and environmental stakeholders.