Polyubiquitin protein of Aedes aegypti as an interacting partner of dengue virus envelope protein.

Dengue virus (DENV) is an arbovirus that comprises four antigenically different serotypes. Aedes aegypti (Diptera: Culicidae) acts as the principal vector for DENV transmission, and vector control is crucial for dengue fever epidemic management. To design effective vector control strategies, a comprehensive understanding of the insect vector and virus interaction is required. Female Ae. aegypti ingests DENV during the acquisition of a blood meal from an infected human. DENV enters the insect midgut, replicates inside it and reaches the salivary gland for transmitting DENV to healthy humans during the subsequent feeding cycles. DENV must interact with the proteins present in the midgut and salivary glands to gain entry and accomplish successful replication and transmission. Ae. aegypti midgut cDNA library was prepared, and yeast two-hybrid screening was performed against the envelope protein domain III (EDIII) protein of DENV-2. The polyubiquitin protein was selected from the various candidate proteins for subsequent analysis. Polyubiquitin gene was amplified, and the protein was purified in a heterologous expression system for in vitro interaction studies. In vitro pull-down assay presented a clear interaction between polyubiquitin protein and EDIII. To further confirm this interaction, a dot blot assay was employed, and polyubiquitin protein was found to interact with DENV particles. Our results enable us to suggest that polyubiquitin plays an important role in DENV infection within mosquitoes.

Genetic Characterization of the Dengue Virus Type 3 Genotype I Prevailing in Dhaka, Bangladesh, 2021.

Background: In Bangladesh, dengue has been prevalent since its resurgence in 2018, and the dominant causative virus in 2019 was considered dengue virus serotype 3 (DENV-3). However, limited information is available for DENV serotype/genotype circulating after 2020. Materials and Methods: Viral RNA was extracted from NS1 antigen-positive blood samples of febrile patients in Dhaka, in 2021. DENV gene was detected by semi-nested RT-PCR, and sequences of envelope (E) gene and C-prM gene were determined by direct sequencing of RT-PCR products for genetic analysis. Results: Among 172 NS1-positive samples collected, 91 samples were assigned to DENV-3 and DENV-2 (88 and 3 samples, respectively) by RT-PCR targeting the C-prM gene. Phylogenetic analysis of the E gene for the 17 representative DENV-3 samples showed that all the viruses belonged to genotype I, forming a cluster (B-cluster) with those of DENV-3 reported in Bangladesh in 2017. Analysis of the deduced amino acid sequences of E protein revealed 16 amino acid substitutions, including two novel ones (G221W, L285P), and a substitution T223I that was specifically found in DENV-3 B-cluster. Conclusion: This study showed the persistent predominance of DENV-3 genotype I in Bangladesh having unique genetic traits in the E gene. (Approval number: MMC/IRB/2022/468).

Replication of Dengue Virus 4 in Plodia interpunctella (Lepidoptera: Pyralidae) Larvae Under Laboratory Conditions.

Background: Developing methods for the isolation and replication of dengue virus (DENV), based on nonhematophagous insect models to assess virus-host interaction, would contribute, for instance, to the creation of drugs or vaccines and eventually to the control of the disease. In this regard, nonhematophagous mosquitoes have been used as biological hosts for the isolation of DENV because they are specific and sensitive to a low viral load and viral particles with low infectivity. However, implementation of these models is mainly affected by the complexity of the establishment of the entomological colonies. Materials and Methods: In this study, the susceptibility of DENV-4 infection in Plodia interpunctella larvae was evaluated. Ten larvae, previously inoculated with supernatant from DENV-4-infected C6/36 cells, were processed to determine viral replication by the optical density and 2-ΔΔCt methods at different time intervals (1 and 7 days postinoculation). Results: A prospective increase in viral replication was observed, which did not influence the survival and development of P. interpunctella. Conclusion: These results demonstrate the infectivity of DENV-4 in P. interpunctella, thus becoming an option as a biological model for the study of this etiological agent.

Molecular Detection of Dengue Virus, Zika Virus, and Chikungunya Virus Arboviruses in Neotropical Bats.

Background: The dengue, Zika, and Chikungunya arboviruses have spread in America in the past year, thus becoming global health issues. These viruses are maintained in nature in two transmission cycles: an urban cycle, transmitted from hematophagous mosquitoes to humans, and a wild cycle, recorded only in Africa and Asia, involving mosquitoes and nonhuman primates as natural hosts. The evidence shows that these arboviruses infect other wild mammals in America, such as rodents, marsupials, and bats. This study aimed to determine the potential natural infection of arboviruses in bats captured in contrasting sites (tropical forests, urban areas, and caves) in Oaxaca, Mexico. Materials and Methods: Liver samples were collected from some bats and tested for RNA from dengue, Zika, and Chikungunya with the quantitative real-time PCR assay. We analyzed 162 samples that encompassed 23 bat species. Results: No natural infection with any of the three arboviruses was detected in any sample tested. Conclusion: The existence of a wild cycle of the three arboviruses in the American continent is not ruled out. However, owing to the low or zero prevalence recorded in other studies and the present study, bats are likely involved in the arbovirus transmission cycle as accidental hosts.

The Density of Aedes albopictus in a High-Latitude and High-Risk Dengue Fever Transmission Region in Shandong Province, Northern China.

Background: A total of 79 cases of dengue fever were reported in Jining County in 2017, which is currently the northernmost focal point of local cases of dengue fever diagnosed in China. This study aimed to evaluate the density of mosquito vectors before and after the outbreak of dengue fever and provide novel reference data for the prevention and control of the disease. Methods: The light traps were set to collect mosquitoes in 2017 and 2018 to assess adult mosquito density and species composition. We used the human-baited double net trap to determine the biting rate. In addition, the Breteau index (BI) was calculated to evaluate the density of Aedes albopictus in Jining, Shandong Province. The annual average densities of Ae. albopictus in 2017 and 2018 were 0.046 and 0.066 f/t/h, respectively. Results: The average biting rate was 0.69 f/m/h in 2018. There was no significant difference found in Ae. albopictus density and biting rate in the various months. The average BI of Jining was 38.67 and 11.17, respectively. There was a statistically significant difference observed in the BI between 2017 and 2018 (Kruskal-Wallis test, χ2 = 16.926, df = 1, p < 0.001). Conclusion: BI can serve as an important indicator to determine the spread of dengue fever. The findings indicted that the growing density of adult Aedes mosquitoes should be focused on, with biting rates being a potential indicator of future outbreaks. Overall, the various control measures that were implemented were effective and should be introduced in other high-risk areas.

Isolation and Genetic Evolution of Dengue Virus from the 2019 Outbreak in Xishuangbanna, Yunnan Province, China.

Background: Dengue virus (DENV) can be divided into four serotypes-DENV-1, DENV-2, DENV-3, and DENV-4. In humans, infection leads to dengue fever (DF), dengue hemorrhagic fever, and dengue shock syndrome, both widely prevalent in tropical and subtropical regions. In 2019, a severe outbreak of DF occurred in Xishuangbanna, Yunnan province. Objective: To investigate the etiology and genotype of the causative agents of this severe dengue outbreak in Xishuangbanna. Methods: Between October and November 2019, the sera of patients clinically diagnosed with DF were collected in the first People's Hospital of Xishuangbanna. RNA was extracted from the sera and amplified by RT-PCR with flavivirus primers. Flavivirus-positive sera were then used to inoculate Aedes albopictus cells (C6/36); viral RNA was extracted from these cells, amplified, and sequenced with DENV E gene-specific primers. Sequence splicing and nucleotide homology genetic evolution analysis were carried out by biological software (DNAStar). Unique mutations in the E genes of isolated DENV were analyzed by SWISS-MODEL and PyMOL. Results: Of the 60 samples collected from DF patients, 39 tested positively with flavivirus primers. The DENV was isolated from 25 of the 39 positive seras, of which 20 showed cytopathic effects (CPE) and 5 were no CPE. In these 25 isolated nucleic acids, 21 strains of DENV-1, 3 strains of DENV-2, and 1 strain of DENV-3 were identified according to the sequence of E protein. In the four unique mutations (D52, Y149, L312, T386), D52 and Y149 in the E protein of DENV-1 were predicted to be exposed on the surface of the prefusion conformation. Conclusion: The 2019 outbreak of DF in Xishuangbanna area of Yunnan Province consists of at least three serotypes of DENV-1, DENV-2, and DENV-3, and the sources of these virus strains are of mixed and complicated origin.

Satellite observation to assess dengue risk due to Aedes aegypti and Aedes albopictus in a subtropical city of Argentina.

Earth observation environmental features measured through remote sensing and models of vector mosquitoes species Aedes aegypti and Ae. albopictus provide an advancement with regards to dengue risk in urban environments of subtropical areas of Argentina. The authors aim to estimate the effect of landscape coverage and spectral indices (Normalized Difference Vegetation Index [NDVI], Normalized Difference Water Index [NDWI] and Normalized Difference Built-up Index [NDBI]) on the larvae abundance of Ae. aegypti and Ae. albopictus in Eldorado, Misiones, Argentina using remote satellite sensors. Larvae of these species were collected monthly (June 2016 to April 2018), in four environments: tire repair shops, cemeteries, dwellings and an urban natural park. The proportion of landscape coverage (water, urban areas, bare soil, low vegetation and high vegetation) was determined from the supervised classification of Sentinel-2 images and spectral indices, calculated. The authors developed spatial models of both vector species by generalized linear mixed models. The model's results showed that Ae. aegypti larvae abundance was better modelled by NDVI minimum values, NDBI maximum values and the interaction between them. For Ae. albopictus proportion of bare soil, low vegetation and the interaction between both variables explained better the abundance.

Adaptation of a Human Diagnostic Kit to Detect Dengue, Zika, and Chikungunya Viruses in Mosquito Samples (Aedes aegypti and Aedes albopictus): A Contribution to Public Health in the International Triple Border (Brazil, Paraguay, and Argentina).

Objective: The objective of this work was to adapt a diagnostic kit developed for humans to identify Dengue (DENV1, DENV2, DENV3, DENV4), Zika (ZIKV) and Chikungunya virus (CHIKV) in females of Aedes aegypti and Aedes albopictus and to verify if the occurrence of mosquitoes infected with these three arboviruses are being found in regions with high occurrence of these diseases in humans. Materials and Methods: For this purpose, live mosquitoes were captured between January and June 2020 using 3,476 traps permanently installed in the field were used. After capture, the species were identified, then the females were placed in a pool of 2 to 10 specimens and sent to the laboratory for detection of DENV1, DENV2, DENV3, DENV4, ZIKV and CHIKV by RT-PCR using a commercial human kit for arboviruses. Results: Of the 76 mosquito pools collected, six (7.9%) pools tested positive for the DENV2 virus. The DENV-positive mosquitoes were collected in regions with a high incidence of reported cases of Dengue or in adjacent areas. Conclusion: The absence of kits for the detection of these arboviruses in Aedes is a limiting factor and the adequacy of commercial kits, already used for the diagnosis of arboviruses in humans, the results presented demonstrate that it is possible to identify the presence of DENV2 in mosquitoes with the respective kit, reinforcing the use of RT-qPCR as a robust diagnostic tool for epidemiological surveillance allowing managers to receive timely results for decision-making regarding prevention and control actions.

International shipments of Wolbachia-infected mosquito eggs: towards the scaling-up of World Mosquito Program operations.

The Wolbachia insect control method, employed by the World Mosquito Program (WMP), relies on introgressing Wolbachia through target Aedes aegypti populations to reduce the incidence of dengue. Since 2010, the WMP has been producing Wolbachia-infected mosquitoes at numerous sites across the globe for release in 11 countries. As the technology has matured, greater focus has been placed on mosquito production at larger central facilities for transport to remote release sites, both domestically and internationally. Of particular note is the production of Wolbachia-infected mosquitoes at the WMP's Australian production facility for successful international deployments in Fiji, Vanuatu, Kiribati and Sri Lanka. This requires careful management of both production and supply-chain processes to ensure that the quality of the mosquito eggs, specifically the hatch rate and Wolbachia infection rate, is maintained. To ensure the cost-effectiveness and scalability of the Wolbachia method, these processes will be further refined to facilitate deployment from large centralised production facilities.

La méthode de contrôle des insectes mise en oeuvre par le World Mosquito Program (WMP) recourt à la bactérie Wolbachia et repose sur l'introgression de cette dernière par le biais des populations cibles d'Aedes aegypti dans le but de réduire l'incidence de la dengue. Depuis 2010, le WMP produit des moustiques infectés par Wolbachia à partir de nombreux sites répartis dans le monde entier en vue de leur lâcher dans 11 pays. Cette technologie s'étant bien développée, l'accent est désormais mis sur la production de moustiques dans des établissements centralisés de plus grande envergure afin de les expédier vers des sites de lâcher éloignés, tant sur le territoire national qu'à l'échelle internationale. Il importe de souligner la production de moustiques infectés par Wolbachia conduite par le WMP sur son site australien et leur déploiement international couronné de succès aux Fidji, au Vanuatu, à Kiribati et au Sri Lanka. Cela nécessite une gestion rigoureuse des procédures aussi bien lors de la production que tout au long de la chaîne d'approvisionnement afin de veiller au maintien de la qualité des oeufs de moustiques et plus spécifiquement du taux d'éclosion et du taux d'infection par Wolbachia. Afin d'assurer la rentabilité et l'évolutivité de la méthode basée sur Wolbachia, ces procédures seront encore affinées afin de faciliter le déploiement à partir de sites de production à grande échelle centralisés.

El método de control de insectos con Wolbachia que emplea el World Mosquito Program (WMP) reposa en la introgresión de Wolbachia a través de poblaciones de Aedes aegypti para reducir la incidencia del dengue. Desde 2010, el WMP viene generando mosquitos infectados por Wolbachia en numerosas instalaciones repartidas por todo el globo, mosquitos que después son liberados en 11 países. A medida que la tecnología ha ido madurando, la tendencia ha sido cada vez más la de concentrar la producción de mosquitos en grandes instalaciones centrales y desde allí enviarlos a los remotos lugares de suelta, ya estén en el mismo país o en otros países. Especialmente destacable es la producción de mosquitos infectados por Wolbachia en las instalaciones que el WMP tiene en Australia, utilizadas con éxito como centro de operaciones para aplicar el método en otros países como Fiji, Vanuatu, Kiribati y Sri Lanka. Ello exige una cuidadosa gestión de los procesos tanto de producción como de la cadena de suministro, que garantice un nivel constante de calidad de los huevos de mosquito, y más concretamente de las tasas de eclosión y de infección por Wolbachia. A fin de asegurar que el método ofrezca una buena relación costo-eficacia y sea reproducible a mayor escala, esos procesos serán perfeccionados para facilitar el despliegue de los insectos a partir de grandes instalaciones de producción centralizada.

Multiple insecticide resistance and first evidence of V410L kdr mutation in Aedes (Stegomyia) aegypti (Linnaeus) from Burkina Faso.

The response to recent dengue outbreaks in Burkina Faso was insecticide-based, despite poor knowledge of the vector population's susceptibility to the insecticides used. Here, we report on the susceptibility to the main insecticide classes and identify important underlying mechanisms in Aedes aegypti populations in Ouagadougou and Banfora, in 2019 and 2020. Wild Ae. aegypti were tested as adults in WHO bioassays and then screened in real time melting curve qPCR analyses to genotype the F1534C, V1016I, and V410L Aedes kdr mutations. Ae. aegypti showed moderate resistance to 0.1% bendiocarb (80-95% survival post-exposure), 0.8% Malathion (60-100%), 0.21% pirimiphos-methyl (75% - 97%), and high resistance to 0.03% deltamethrin (20-70%). PBO pre-exposure partially restored pyrethroid susceptibility. Genotyping detected high frequency of 1534C allele (0.92) and moderate 1016I (0.1-0.32). The V410L mutation was detected in Burkina Faso for the first time (frequency 0.1-0.36). Mosquitoes surviving 4 h exposure to 0.03% deltamethrin had significantly higher frequencies of the F1534C mutation than dead mosquitoes (0.70 vs. 0.96, p < 0.0001) and mosquitoes surviving 2 - 4 h exposure had a significantly reduced life span. Ae. aegypti from Burkina Faso are resistant to multiple insecticide classes with multiple mechanisms involved, demonstrating the essential role of insecticide resistance monitoring within national dengue control programmes.

Seasonal variation and intra urban heterogeneity of the entomological risk of transmission of dengue and yellow fever in Abidjan, Côte d'Ivoire.

Dengue and yellow fever are prevalent in Côte d'Ivoire and Aedes (Stegomyia) aegypti (Linnaeus), (Diptera: Culicidae), is known as the main vector. We aimed to assess seasonal variation and spatial heterogeneity in the transmission of both arbovirus diseases in Abidjan. Entomological surveys targeting larvae of A. aegypti, were carried out between November 2015 and August 2016 covering the four climatic seasons including a cohort of 100 houses randomly selected in three neighbourhoods. A. aegypti was the predominant species (96.6%) of mosquitoes resulting from the rearing of harvested larvae, and the only vector of dengue and yellow fever recorded during the study period. The highest proportion of water storage containers (45.5%) which represented the major breeding sites infested by the larvae of A. aegypti, was observed in Anoumabo. The house indices >5% and/or Breteau indices >20 recorded in each neighbourhood, during the different climatic seasons, indicated that there was, a high and permanent, heterogeneity in the transmission risk of dengue and yellow fever between the three neighbourhoods. In terms of transmission risk, Anoumabo was the neighbourhood with the highest risk compared to the two others, then, particular attention should be paid to this site in terms of surveillance by vector control programme in Abidjan.

First Evidence of Horizontal Transmission by Fecal Shedding of Dengue Virus 4 Among Aedes aegypti Larvae (Diptera: Culicidae) Under Laboratory Conditions.

The transmission pathways of dengue virus (DENV) among mosquitoes are a topic that has gained relevance in recent years because they could explain the maintenance of the virus in the wild independently of the human-mosquito horizontal transmission cycle. In this regard, Aedes aegypti larvae exposed to supernatants of C6/36 cells infected with DENV-4 were evaluated for virus excretion in feces and viability of infection in immature stages (larvae). The results demonstrate that larvae excrete DENV-4 in their feces with the potential to at least infect immature individuals of the same species. A horizontal transmission pathway of larvae-larvae DENV-4 under laboratory conditions is suggested.

Assessment of the global circulation and endemicity of dengue.

Dengue is a significant public health issue, affecting hundreds of millions of people worldwide. As it is spreading from tropical and subtropical zones, some regions previously recognised as non-endemic are at risk of becoming endemic. However, the global circulation of dengue is not fully understood and quantitative measurements of endemicity levels are lacking, posing an obstacle in the precise control of dengue spread. In this study, a sequence-based pipeline was designed based on random sampling to study the transmission of dengue. The limited intercontinental transmission was identified, while regional circulation of dengue was quantified in terms of importation, local circulation and exportation. Additionally, hypo- and hyper-endemic regions were identified using a new metric, with the former characterised by low local circulation and increased importation, whereas the latter by high local circulation and reduced importation. In this study, the global circulation pattern of dengue was examined and a sequence-based endemicity measurement was proposed, which will be helpful for future surveillance and targeted control of dengue.

Dengue virus serotype 2 imported case from Côte d'Ivoire to Senegal, 2017.

Dengue fever is the most common arboviral infection worldwide. Its epidemiology in Africa is not yet fully understood due to the lack of awareness, the presence of other dengue-like febrile diseases, and insufficient laboratory capabilities. This paper reports on the import of dengue virus serotype 2 case from Côte d'Ivoire to Senegal in West Africa. Phylogenetic analysis based on full-length genome sequence revealed that the isolate clustered with strains of cosmopolitan genotypes from the Burkina Faso outbreak in 2016 and those from the ongoing dengue fever outbreak in Côte d'Ivoire. This suggests a possible spread of strains from the Burkina Faso outbreak to other West African countries including Côte d'Ivoire and Senegal.

Knowledge, attitude and prevention practices of garment factory workers regarding the largest Dengue outbreak on record in Bangladesh.

The aim of this cross-sectional study was to assess the knowledge, attitudes and prevention practices (KAP) among the garment factory worker population in Bangladesh regarding a historical dengue outbreak in 2019. A total of 400 participants were selected by simple random sampling, and questionnaire-based interviews were conducted. The average score of knowledge, attitude and prevention practice was 8.33 ± 2.35, 6.32 ± 1.20 and 6.31 ± 1.50, respectively. Only 76 out of 400 participants (19%) scored above 10 (all university-educated). Participant workers reported both negative and positive attitudes regarding dengue fever (DF). Negative attitudes included an expectation of increased mortality and strained family finances from DF attacks. A significantly high number of participants (92%) believed that death from DF was inevitable. Positive attitudes included optimism about DF eradication potentials and eagerness to help and donate blood to sick relatives. Participants primarily learned about the DF prevention from mass media (244/400; 61.0%) and social media (97/400; 24.25%). The most popular prevention measures adopted were mosquito repellent incense (344/400; 86.0%) and mosquito nets (389/400; 97.25%). While most participants (358/400; 89.5%) cleaned areas where mosquitos lay eggs, only 169 out of 400 (42.25%) regularly treated with chemical sprays. Only 182 out of 400 (45.5%) reported receiving DF prevention training in the factory. Correlation between DF knowledge and education was statistically significant (r = .38, p < .01, n = 398). Correlation between DF knowledge and work experience was insignificant (r = .01, p > .01, n = 398). Age and DF knowledge were not correlated (r = 0.07, p > .01, n = 398). In conclusion, gaps in KAP for dengue could be addressed by government-sponsored educational programmes that utilize the power of mass/social media for dengue prevention and control. More KAP surveillance studies are needed for other sectors of the society.

Evaluating livestock farmers knowledge, beliefs, and management of arboviral diseases in Kenya: A multivariate fractional probit approach.

Globally, arthropod-borne virus (arbovirus) infections continue to pose substantial threats to public health and economic development, especially in developing countries. In Kenya, although arboviral diseases (ADs) are largely endemic, little is known about the factors influencing livestock farmers' knowledge, beliefs, and management (KBM) of the three major ADs: Rift Valley fever (RVF), dengue fever and chikungunya fever. This study evaluates the drivers of livestock farmers' KBM of ADs from a sample of 629 respondents selected using a three-stage sampling procedure in Kenya's three hotspot counties of Baringo, Kwale, and Kilifi. A multivariate fractional probit model was used to assess the factors influencing the intensity of KBM. Only a quarter of the farmers had any knowledge of ADs while over four-fifths of them could not manage any of the three diseases. Access to information (experience and awareness), income, education, religion, and distance to a health facility considerably influenced the intensity of farmers' KBM of ADs in Kenya. Thus, initiatives geared towards improving access to information through massive awareness campaigns are necessary to mitigate behavioral barriers in ADs management among rural communities in Kenya.

Forest Coverage and Socioeconomic Factors Associated with Dengue in El Salvador, 2011-2013.

Dengue virus serotypes 1, 2, 3, and 4 are transmitted by Aedes aegypti and Aedes albopictus mosquitoes, which cause illness in an estimated 100 million annually. Although dengue viruses are endemic throughout El Salvador, very little is known about their ecology and epidemiology. The principal methods to prevent and reduce dengue cases are through vector control and by adoption of a vaccine. In addition, understanding the environmental and socioeconomic factors associated with dengue could contribute to case reduction by targeting prevention efforts in dengue hotspots. This study investigated environmental and socioeconomic factors associated with dengue cases in El Salvador. Dengue cases were obtained from 2011 to 2013 for 262 municipalities. The mean incidence was determined for each municipality for the 3 year period. Negative binomial regression models evaluated the relationship between dengue cases and the environmental factors elevation, forest coverage, mean annual temperature, and cumulative precipitation. Twelve socioeconomic and infrastructure variables and their relationship with dengue were also investigated by using negative binomial regression. A total of 29,764 confirmed dengue cases were reported. The mean dengue incidence for 2011-2013 was 135/100,000. The highest number of dengue cases occurred in San Salvador and surrounding municipalities, as well as in two additional cities, Santa Ana and San Miguel; the highest incidence of dengue cases (per 100,000) occurred in cities in the west and at the center of the country. Significant environmental variables associated with dengue included temperature, precipitation, and non-forested area. The socioeconomic variables poverty rate, illiteracy rate, and school attendance, and the infrastructure variables percent of homes with sanitary service, municipal trash service, electricity, and cement brick flooring, as well as population density, were also significant predictors of dengue. Understanding these environmental and socioeconomic factors and their relationship with dengue will help design and implement timely prevention strategies and vector control to reduce dengue in El Salvador.

Worldwide dynamic biogeography of zoonotic and anthroponotic dengue.

Dengue is a viral disease transmitted by mosquitoes. The rapid spread of dengue could lead to a global pandemic, and so the geographical extent of this spread needs to be assessed and predicted. There are also reasons to suggest that transmission of dengue from non-human primates in tropical forest cycles is being underestimated. We investigate the fine-scale geographic changes in transmission risk since the late 20th century, and take into account for the first time the potential role that primate biogeography and sylvatic vectors play in increasing the disease transmission risk. We apply a biogeographic framework to the most recent global dataset of dengue cases. Temporally stratified models describing favorable areas for vector presence and for disease transmission are combined. Our models were validated for predictive capacity, and point to a significant broadening of vector presence in tropical and non-tropical areas globally. We show that dengue transmission is likely to spread to affected areas in China, Papua New Guinea, Australia, USA, Colombia, Venezuela, Madagascar, as well as to cities in Europe and Japan. These models also suggest that dengue transmission is likely to spread to regions where there are presently no or very few reports of occurrence. According to our results, sylvatic dengue cycles account for a small percentage of the global extent of the human case record, but could be increasing in relevance in Asia, Africa, and South America. The spatial distribution of factors favoring transmission risk in different regions of the world allows for distinct management strategies to be prepared.

Phage display demonstrates durable differences in serological profile by route of inoculation in primary infections of non-human primates with Dengue Virus 1.

Natural dengue virus (DENV) infections occur by mosquito bite but how the inoculation route affects the humoral immune response is unknown. We serologically profiled 20 non-human primates (NHP) from a prior study of DENV1 infection where animals were inoculated by mosquito (N = 10) or subcutaneous injection (N = 10). Using a comprehensive, densely tiled and highly redundant pan-flavivirus programmable phage library containing 91,562 overlapping 62 amino acid peptides, we produced a high-resolution map of linear peptide sequences enriched during DENV seroconversion. Profiles in mosquito-inoculated and subcutaneously-inoculated animals were similar up to 90 days after primary infection, but diverged at 1 year with differences in sero-reactivity in the Envelope (E; residues 215-406; p < 0.08), and Nonstructural-3 (NS3; residues 549-615; p < 0.05) proteins in mosquito-inoculated versus subcutaneously-inoculated animals. Within the E protein, residues 339-384 in domain III accounted for > 99% of the observed sero-reactivity difference. Antibody breadth did not vary by mode of inoculation. The differential reactivity to E domain III seen by phage display validated orthogonally by ELISA, but did not correlate with late neutralization titers. Serological profiling of humoral immune responses to DENV infection in NHP by programmable phage display demonstrated durable differences in sero-reactivity by route of inoculation.

Co-Circulation of All Four Dengue Viruses and Zika Virus in Guerrero, Mexico, 2019.

A clinical and entomological investigation was performed to identify flavivirus infections in humans and mosquitoes in impoverished areas of Guerrero, a coastal state in southwestern Mexico. A total of 639 patients with acute febrile illness and 830 resting female mosquitoes in low-income communities of Guerrero in 2019 were tested for evidence of flavivirus infection. Sera were collected from all patients and screened at a dilution of 1:20 by plaque reduction neutralization test (PRNT) using dengue virus (DENV)2. A total of 431 (67.4%) patients were seropositive. Sera from a subset of seropositive patients (n = 263) were tested for flavivirus NS1 by enzyme-linked immunosorbent assay. Forty-eight (18.3%) sera contained viral antigen. All NS1-positive sera were titrated and further tested by PRNT using DENV-1 to -4, St. Louis encephalitis virus, West Nile virus, and Zika virus (ZIKV). Seven patients were seropositive for DENV-1, five patients were seropositive for DENV-2, one patient was seropositive for DENV-3, and two patients each were seropositive for DENV-4 and ZIKV. The remainder had secondary flavivirus infections or antibodies to an undetermined flavivirus. Comparative PRNTs were also performed on 60 randomly selected NS1-negative sera, identifying patients seropositive for DENV-2, DENV-3, and ZIKV. The entomological investigation yielded 736 Aedes aegypti and 94 Culex quinquefasciatus that were sorted into 183 pools and 20 pools, respectively. Mosquitoes were assayed for flavivirus RNA by RT-PCR and Sanger sequencing. DENV-2 RNA was detected in three pools of A. aegypti. In summary, we provide evidence for the concurrent circulation of all four DENVs and ZIKV in Guerrero, Mexico. The public health authorities reported no cases of DENV-3, DENV-4, and ZIKV in Guerrero in 2019 and thus, we provide evidence of under-reporting in the region.