Dengue Endemic Areas Research Articles

Evaluation of coinfection between SARS-CoV-2 and dengue virus in São Luís/MA

The COVID-19 pandemic has become a global public health emergency, especially in subtropical regions endemic for arboviruses. During the acute phase of the disease, Dengue and COVID-19 present similar laboratory profiles and symptomatology, complicating clinical diagnosis. This study analyzed the occurrence of coinfections between dengue virus and SARS-CoV-2 in patients treated at a laboratory in São Luís, Maranhão. A total of 150 random serum samples from patients, collected between April and May 2020, tested positive for IgM/IgA antibodies against SARS-CoV-2. For the detection of dengue virus (DENV), reactions were standardized using specific primers for each serotype (1-4). Subsequently, cDNA amplification was performed by conventional PCR, and the amplicons were analyzed by agarose gel electrophoresis. Through this study, it was possible to identify one sample (0.6%) positive for the DENV-4 serotype. This study validates the possibility of coinfections in dengue-endemic areas.

Detection of Insecticide Resistance in Aedes aegypti from Dengue Endemic Areas of Northern India

Detection of Insecticide Resistance in Aedes aegypti from Dengue Endemic Areas of Northern India

Under-Reporting of Human Leptospirosis Cases in Cities of Triângulo Mineiro, Minas Gerais, Brazil.

Leptospirosis is an infectious disease caused by the pathogenic Leptospira species through direct or indirect contact with infected animals. Due to protean clinical manifestation in the early stages, leptospirosis is often difficult to distinguish from other common acute febrile illnesses, such as dengue. Thus, this study aimed to investigate the prevalence of leptospirosis in suspected dengue patients whose serological diagnosis was negative. A total of 449 serum samples from patients (negative IgM-ELISA dengue) with fever, headache, myalgia, and nausea were tested. The Dual-Path Platform (DPP) rapid test developed by the Instituto de Tecnologia em Imunobiológicos Bio-Manguinhos in the city of Rio de Janeiro, Brazil was used for screening IgM antibodies against Leptospira in blood serum, and the microscopic agglutination test (MAT) was performed on samples positive in the DPP for leptospirosis, as well as on an equal number of negative samples. Results: The data obtained from the samples analyzed with the DPP assay showed 26 positive results (5.79%), of which 38.46% were male and 61.54% female, with a mean age of 41 years. We tested 52 samples using the MAT, including 26 reactive for IgM and 26 non-reactive in the DPP assay. Nine samples (17.31%) were reactive, and among them, six also showed reactivity in the DPP assay. Of the six samples reactive in both tests, 66.67% were female, living in urban areas in the city of Uberlândia, with a mean age of 50 years, being 50% white, 33.33% brown, and 16.67% black. The findings demonstrated that leptospirosis cases are underdiagnosed and undertreated in the study population and more attention needs to be paid for ruling out leptospirosis and other pathogens causing acute febrile illness in dengue-endemic areas.

Wolbachia infection in Aedes aegypti does not affect its vectorial capacity for Dirofilaria immitis.

Mosquito-borne diseases such as dengue and filariasis are a growing public health concern in endemic countries. Biological approaches, such as the trans-infection of Wolbachia pipientis in mosquitoes, are an alternative vector control strategy, especially for arthropod-borne viruses such as dengue. In the present study, the effect of Wolbachia (wMel strain) on the vectorial capacity of Aedes aegypti for Dirofilaria immitis was studied. Our results showed that Wolbachia does not affect the phenotype of mosquito survival or the prevalence, number, and molting rate of third-stage larvae in both susceptible and resistant strains of Ae. aegypti. RNA-seq analysis of Malpighian tubules at 2days post-infection with D. immitis showed the differentially expressed genes (DEGs) with and without wMel infection. No characteristic immune-related gene expression patterns were observed among the DEGs. No significant change in the amount of Wolbachia was observed in the Ae. aegypti after D. immitis infection. Our results suggest that infection of D. immitis in Ae. aegypti populations will not interfere with Wolbachia-based vector control strategies in dengue-endemic areas where cases of D. immitis are present. This study demonstrated the veterinary medical validity of a dengue control program using Wolbachia.

Impact of climate change on vector-borne diseases: Exploring hotspots, recent trends and future outlooks in Bangladesh

Climate change is a significant risk multiplier and profoundly influences the transmission dynamics, geographical distribution, and resurgence of vector-borne diseases (VBDs). Bangladesh has a noticeable rise in VBDs attributed to climate change. Despite the severity of this issue, the interconnections between climate change and VBDs in Bangladesh have yet to be thoroughly explored. To address this research gap, our review meticulously examined existing literature on the relationship between climate change and VBDs in Bangladesh. Using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) approach, we identified 3849 records from SCOPUS, Web of Science, and Google Scholar databases. Ultimately, 22 research articles meeting specific criteria were included. We identified that the literature on the subject matter of this study is non-contemporaneous, with 68% of studies investing datasets before 2014, despite studies on climate change and dengue nexus having increased recently. We pinpointed Dhaka and Chittagong Hill Tracts as the dengue and malaria research hotspots, respectively. We highlighted that the 2023 dengue outbreak illustrates a possible shift in dengue-endemic areas in Bangladesh. Moreover, dengue cases surged by 317% in 2023 compared to 2019 records, with a corresponding 607% increase in mortality compared to 2022. A weak connection was observed between dengue incidents and climate drivers, including the El Niño Southern Oscillation (ENSO) and Indian Ocean Dipole (IOD). However, no compelling evidence supported an association between malaria cases, and Sea Surface Temperature (SST) in the Bay of Bengal, along with the NINO3 phenomenon. We observed minimal microclimatic and non-climatic data inclusion in selected studies. Our review holds implications for policymakers, urging the prioritization of mitigation measures such as year-round surveillance and early warning systems. Ultimately, it calls for resource allocation to empower researchers in advancing the understanding of VBD dynamics amidst changing climates.

Clinical Picture and Risk Factors for Severity of SARS-CoV-2 and Dengue Coinfection in Children: Experience From a Tertiary Hospital in Vietnam.

Introduction Dengue is an infectious disease that is a burden in Asia-Pacific and Latin America. The COVID-19 pandemic in dengue-endemic areas has caused a "double burden" because of the possibility of coinfection, especially in children who are vulnerable to both COVID-19 and dengue. This study aimed to describe the characteristics and identify risk factors for the severity of the coinfection in Vietnamese children. Methods This was a retrospective cohort study, undertaken at Children's Hospital 1 (Ho Chi Minh City, Vietnam) during the fourth wave of the COVID-19 pandemic. All children under 16 years old who were admitted to the hospital from April 27, 2021 to June 30, 2022, and diagnosed with SARS-CoV-2 and dengue coinfection were included. Results From April 2021 to June 2022, a total of 31 patients with the coinfection were included, with 19 of them being male (61.3%). The median age was 10.8 years old (IQR, 5.1-14.1). Fourteen children (45.2%) had preexisting comorbidities, with the most common comorbidity being overweight/obesity (ten children). Nearly two-thirds of the children were diagnosed with dengue without/with warning signs (61.3%) and were classified as having mild COVID-19 (83.9%). The most frequently observed clinical characteristics were fever (n=29, 93.6%), followed by abdominal pain, vomiting, and petechiae. All patients had high serum ferritin, and 83.9% presented with thrombocytopenia. None of thecases died. Overweight/obesity, abdominal pain, and petechiae were factors independently associated with severe disease. Conclusion Most of the children had mild COVID-19 and disease progression similar to patients with dengue alone. However, some children may have severe COVID-19 and dengue coinfection. Obesity, abdominal pain, and petechiae were identified as independent risk factors for disease severity in pediatric cases. Further studies with multicenters and a larger sample size are needed to assess the coinfection more thoroughly.

Immunogenicity, safety, and efficacy of a tetravalent dengue vaccine in children and adolescents: an analysis by age group.

Dengue is an increasing threat to global health. This exploratory analysis evaluated the immunogenicity, safety, and vaccine efficacy (VE) of a live-attenuated tetravalent dengue vaccine (TAK-003) in participants enrolled in the phase 3 DEN-301 trial (NCT02747927), stratified by baseline age (4-5 years; 6-11 years; or 12-16 years). Participants were randomized 2:1 to receive 2 doses of TAK-003, administered 3 months apart, or placebo. Dengue serostatus was evaluated at enrolment. VE against virologically-confirmed dengue (VCD) and hospitalized VCD; immunogenicity (geometric mean titers; GMTs); and safety were evaluated per age group through ∼4 years post-vaccination. VE against VCD across serotypes was 43.5% (95% confidence interval: 25.3%, 57.3%) for 4-5 year-olds; 63.5% (56.9%, 69.1%) for 6-11 year-olds, and 67.7% (57.8%, 75.2%) for 12-16 year-olds. VE against hospitalized VCD was 63.8% (21.1%, 83.4%), 85.1% (77.1%, 90.3%), and 89.7% (77.9%, 95.2%), for the three age groups, respectively. GMTs remained elevated against all four serotypes for ∼4 years post-vaccination, with no evident differences across age groups. No clear differences in safety by age were identified. This exploratory analysis shows TAK-003 was efficacious in dengue prevention across age groups in children and adolescents 4-16 years of age living in dengue endemic areas. Relatively lower VE in 4-5 year-olds was potentially confounded by causative serotype distribution, small sample size, and VE by serotype, and should be considered in benefit-risk evaluations in this age group.

Severe COVID-19 multisystem inflammatory syndrome versus severe dengue in children from Indonesia: a cross-sectional study

IntroductionSevere multisystem inflammatory syndrome in children (MIS-C) and severe dengue are challenging to identify during the COVID-19 pandemic in dengue-endemic areas. Fever, multiorgan involvement, and shock characterize both severe MIS-C and severe dengue. Distinguishing between the two diseases is beneficial in initiating proper management.MethodsMedical records of children < 18 years old who were hospitalized at Hasan Sadikin General Hospital’s PICU between December 2020 and July 2022 with severe MIS-C or severe dengue were recorded. Differences were assessed using comparative and descriptive analyses.ResultsSeventeen severe dengue patients and 4 severe MIS-C were included. The average age of severe MIS-C was 11.5 years (SD ± 2.9, 95% CI), and that of severe dengue patients was 6.2 years (SD ± 4.4, 95% CI) (p value = 0.034, 95%). Fever and abdominal pain were the most common symptoms in both groups (p = 0.471, 95% CI). Rash (p = 0.049) and nonpurulent conjunctivitis (p = 0.035) were two symptoms with significant differences. The highest platelet count (p-value = 0.006, 95% CI), AST (p-value = 0.026, 95% CI), and D-dimer level (p-value = 0.025, 95% CI) were significantly different between the two cohorts. Cardiac abnormalities were found in all (100%) severe MIS-C patients, but only one (5.9%) in severe dengue patients.ConclusionAge, rash, nonpurulent conjunctivitis, platelet count, AST and D-dimer level may distinguish severe MIS-C from severe dengue fever.

Physico-chemical characteristics of breeding habitats in relation to larval density and relative abundance of Aedes mosquitoes from Siliguri sub-division, West Bengal, India

Aim: Characterization of physico-chemical parameters of Aedes mosquito breeding habitats from dengue-endemic Siliguri sub-divisional area and correlation of larval density with the habitat characteristics. Methodology: Natural and artificial water-holding containers found in four blocks, namely- Naxalbari, Matigara, Khoribari and Phansidewa of Siliguri sub-divisional area were surveyed for the collection of Aedes mosquito larvae. Water parameters such as pH, temperature, electric conductance (EC), total dissolved solid (TDS), chloride, salinity, total hardness (TH) and dissolved oxygen (DO) were measured and the larval density (LD) indices and relative abundance for Aedes spp., were calculated. Results: Out of 40 habitats, larvae of Aedes spp. were found in 20 habitats (50%). Ae. albopictus was found as the pre-dominant species (81.24%) in all the positive breeding habitats. Three habitat characteristics, like chloride (r= -0.959; p= 0.041), salinity (r= -0.958; p= 0.041)and TH (r= -0.961; p= 0.039) showed significant negative association with larval densityin the study. Whereas the remaining parameters, like-pH, temperature, EC, TDS, were positively correlated and DO showed a negative correlation with larval density. Although none of the later correlations were statistically significant. The larval density of Aedes spp. (mean ± SD) was lowest in Khoribari (27.66 ± 21.55) and highest in Phansidewa block (128.33 ± 187.26). Interpretation: Pre-dominance of Ae. albopictus reiterates its importance as a principal dengue vectorin rural, peri- or sub-urban area of the sub-division. Utilizing the obtained data, the efficacy of oviposition traps can be enhanced for locale-specific vector surveillance and development of novel techniques that may deter larval growth, development and survival in an area. Key words: Aedes mosquitoes, Dengue, Larval density, Mosquito-borne viral diseases, Siliguri

Exploring the Chikungunya virus landscape in a dengue-endemic Brazilian area

We aimed to describe the landscape, including molecular, epidemiological, and clinical aspects of CHIKV infections in the Ribeirao Preto region, an area endemic to dengue. We randomly screened 3744 plasma samples that had undergone DENV diagnosis to evaluate CHIKV-RNA using an in-house RT-PCR assay. Positive samples were followed clinically, and RNA samples were submitted to whole genome sequencing. Seventeen cases (0.5 %) were positive for CHIKV-RNA despite being negative for DENV-RNA. Notably, half of the patients experienced prolonged arthralgia lasting more than 90 days. Compared with the healthy control group, leukopenia and thrombocytopenia were observed in all CHIKV-positive individuals with statistically significant P values (P < 0.0001 and P = 0.0003, respectively). The genomic analysis revealed that the CHIKV strains being studied are classified within the East-Central-South-African (ECSA) genotype. This analysis identified new mutations, E1: K211E and E2: V264A, while the previously known mutation E1: A226V was not detected among these strains. This study highlights the need for epidemiological surveillance and preparedness for potential CHIKV epidemics in Brazil, particularly where other arboviruses co-circulate.

Evolution of Zika prevalence in a dengue hyperendemic municipality in Southern Mexico after the outbreak of 2015 to 2017

Objective. Estimate the Zika prevalence in a dengueendemic municipality in Mexico, after the outbreak of 2015 to 2017. Materials and methods. Three serosurveys were conducted in Tapachula, Chiapas, in September 2018, March 2019 and November 2019. A commercial ZIKV and DENV anti-NS1 IgG ELISA were used to estimate each prevalence, their performance and adjustment of the cut-off value were compared with an in-house DENVs and ZIKV anti-EDIII IgG ELISA and the microneutralization test. Results. The anti-NS1 ZIKV titers decreased over time, causing that Zika prevalence decreased from 78.02 to 45.22%, while anti-NS1 DENV titers increased, and the prevalence remained above 95% over a two-year period. Conclusion. Optimal Zikaprevalence estimates can be obtained in a two-years period after outbreaks in dengue-endemic areas. The extension of the Zika outbreak is significantly higher than previously reported in Tapachula, highlighting the underreport of cases based on the routine flavivirus surveillance system in Mexico.

Ophthalmic manifestations as the first presenting feature in dengue fever: a 10-year study.

Purpose: To report patients who first presented with various ocular manifestations and eventually ascertained to have underlying dengue. Methods: A prospective study was conducted at multiple tertiary eye-care centers in India from 2012 to 2022. Cases reporting initially with ocular features along with fever/past history of fever over the last two weeks or with clinical features of dengue were selected. After an ophthalmological examination, patients underwent complete serological and biochemical analysis and those with reduced platelet counts were evaluated for dengue. Results: Out of 564 cases, 15 patients were verified to be afflicted with dengue eventually. A rising trend of cases was seen every year and out of 15 cases, eight cases were reported during the Covid-19 pandemic (from 2020 to 2022), but were COVID-negative. 9 cases presented with acute redness followed by diminished vision. Seven cases presented a history of fever over the last few days and one had traveled from dengue endemic area. The various ocular presentations included subconjunctival hemorrhage, viral keratitis, anterior uveitis, sixth-nerve palsy, and vitreous hemorrhage. On serological examination, all 15 patients were detected to have low platelets. All cases responded well with supportive treatment and the ocular features subsided in all within a couple of weeks with good visual recovery. Conclusion: In a tropical nation, such as India, with endemic dengue zones and increasing figures of dengue lately, ophthalmologists must include dengue fever among the differential diagnoses in various ocular presentations like subconjunctival hemorrhage, viral keratitis, anterior uveitis, sixth nerve palsy, and vitreous hemorrhage. Abbreviations: DHF = dengue hemorrhagic fever, PCR = polymerase chain reaction, RT-PCR = real-time automated reverse transcriptase (RT-PCR), SD = standard deviation, MAC-ELIS = IgM antibodies capture enzyme-linked immunosorbent assay, RE = right eye, LE = left eye, CECT = Contrast-enhanced computed tomography.

Polymer Beads Increase Field Responses to Host Attractants in the Dengue Vector Aedes aegypti.

This study investigates the efficacy of three different olfactory cues - cyclohexanone, linalool oxide (LO), and 6-methyl-5-heptan-2-one (sulcatone) - in attracting Aedes aegypti, the primary vector of dengue, using BG sentinel traps in a dengue-endemic area (urban Ukunda) in coastal Kenya. Two experiments were conducted. Experiment 1 compared solid formulations of the compounds in polymer beads against liquid formulations with hexane as the solvent. CO2-baited traps served as controls. In Experiment 2, traps were baited with each compound in the polymer beads, commercial BG-Lure, and CO2. Our results indicate that CO2-baited traps recorded the greatest Ae. aegypti captures in both Experiment 1 and 2, whereas trap captures with polymer beads and solvent-based treatments were comparable. In experiment 2, polymer bead-based treatments yielded significantly greater female captures, each recording ~ 2-fold more captures than traps baited with the BG-Lure. There was no significant difference, however, between the treatments. Female Ae. aegypti captured in CO2-baited traps were mainly unfed (91%), with fewer gravid mosquitoes (6.4%) compared to traps with test compounds (range; 12.7-21.1%). Male captures were lower in LO and BG-Lure baited traps compared to other treatments. Gravimetric analysis showed LO had a slower release rate compared to other compounds. The findings suggest that host-associated compounds loaded on polymer beads are more effective in trapping Ae. aegypti than commercial BG-Lure and reveal sex-specific differences in mosquito responses. These results have implications for mosquito surveillance and control programs, highlighting the potential for selective trapping strategies.

Use of Household Insecticides against Mosquitoes in Dengue-Endemic Areas in Sri Lanka.

The use of household insecticides in the formulation of mosquito coils and vaporizers is common among the public to protect against mosquito-borne diseases. However, information regarding the use of these commonly practiced household insecticides is scarce in Sri Lanka. A questionnaire-based survey was directed to 600 households in Colombo, Gampaha, Kandy, Kalutara, Jaffna, and Galle districts in Sri Lanka. Household insecticides were used by the majority of the respondents (57.0%), and electric liquid vaporizers (46.7%) and mosquito coils (45.7%) were the commonly used forms. The active ingredients in mosquito coils were d-trans-allethrin (w/w 0.12%), metofluthrin (w/w 0.005%), and dimefluthrin (w/w 0.01%); in liquid vaporizers, they were prallethrin (w/v 1.24% and w/v 1.26%) and transfluthrin (w/v 0.9%). The majority of the household insecticide consumers were moderately satisfied with the effectiveness of the products (68.6%), and most of the participants used household insecticides daily (35.5%), especially during the evening (41.6%). Most of the consumers were unaware of the chemicals included in household insecticides (62.8%). Mosquito coils were abundantly used by rural area participants (75.8%), whereas liquid vaporizers were the most common among the urban participants (56.4%). The findings indicate that demographic and socioeconomic factors influence household insecticide practices. To our knowledge, this study reveals the use of household insecticides to control mosquitoes for the first time in Sri Lanka and highlights the importance of awareness programs and the proper utilization of these products.

Seroprevalence and clinical manifestations of Chikungunya infection in Makassar city, Indonesia

Background: Chikungunya is a vector-borne disease with a high morbidity rate, spread in dengue hemorrhagic fever endemic areas because the vector carrying the virus is transmitted by the same mosquitoes, namely Aedes Aegypti and Aedes Albopictus. The number of mosquito breeding sites is often associated with an increased incidence of chikungunya disease. The proximity of mosquito breeding sites to human habitation is a significant risk factor for chikungunya. Data related to chikungunya is still lacking in Makassar. This study aims to understand the prevalence of CHIKV infection through serodiagnosis by measuring CHIKV IgG antibodies and looking at the history of clinical symptoms associated with CHIKV infection in Makassar to reduce widespread transmission.

Geographic information system-aided evaluation of epidemiological trends of dengue serotypes in West Bengal, India.

West Bengal is a dengue-endemic State in India, with all four dengue serotypes in co-circulation. The present study was conceived to determine the changing trends of circulating dengue virus (DENV) serotypes in five consecutive years (2015-2019) using a geographic information system (GIS) during the dengue season in West Bengal, India. Molecular serotyping of dengue NS1 sero-reactive serum samples from individuals with ≤5 days of fever was performed using conventional nested reverse transcriptase-PCR. GIS techniques such as Getis-Ord Gi* hotspot analysis and heatmap were used to elucidate dengue transmission based on the received NS1-positive cases and vector data analysis was used to point out risk-prone areas. A total of 3915 dengue NS1 sero-positive samples were processed from most parts of West Bengal and among these, 3249 showed RNA positivity. The major circulating serotypes were DENV 3 (63.54%) in 2015, DENV 1 (52.79%) in 2016 and DENV 2 (73.47, 76.04 and 47.15%) in 2017, 2018 and 2019, respectively. Based on the NS1 positivity, dengue infections were higher in males than females and young adults of 21-30 yr were mostly infected. Getis-Ord Gi* hotspot cluster analysis and heatmap indicate that Kolkata has become a hotspot for dengue outbreaks and serotype plotting on maps confirms a changing trend of predominant serotypes during 2015-2019 in West Bengal. Co-circulation of all the four dengue serotypes was observed in this study, but only one serotype became prevalent during an outbreak. Representation of NS1-positive cases and serotype distribution in GIS mapping clearly showed serotypic shift in co-circulation. The findings of this study suggest the need for stringent surveillance in dengue-endemic areas to limit the impact of dengue and implement better vector-control strategies.

Arbovirus Detection of Adult Female &lt;i&gt;Aedes aegypti&lt;/i&gt; for Dengue Surveillance: a Cohort Study in Bandung City, Indonesia

Dengue surveillance is an important activity to prevent dengue outbreaks. This activity becomes a significant challenge for the region with limited logistic capabilities. Developing a simple mathematical model to predict the possibility of dengue incidence provides a reliable early warning system. This study compared the correlation between vector (adult female Aedes aegypti) and arbovirus detection on a vector to dengue incidence, which generalized linear mixed models tested. The incidence of adult female Aedes aegypti and dengue fever cases were interpolated through third-power inverse distance weighting (IDW). A spatial correlation between female Aedes aegypti incidence and dengue incidence was obtained from polynomial regression. Collection sites were 16 villages in Bandung city, one of the significant dengue endemic areas in January–December 2017. A total of 8,402 mosquitoes of Aedes aegypti, Aedes albopictus, and Culex sp., with 17% belonging to Aedes aegypti as the subject of the dengue virus (DENV) infection test. Data analysis only showed a weak correlation between the numbers of adult female Aedes aegypti and dengue incidence. On the other hand, there is no correlation between positive dengue infection of vector and dengue incidence. This study highlights the importance of constant arbovirus surveillance and integrated surveillance methods on all possible dengue vectors to develop an early warning system for dengue incidence.

Flood and Dengue: Increased risk of Gestational Pestilences.

Madam Editor, Dengue fever is an acute viral disease caused by an RNA (Ribonucleic Acid) virus transmitted by Aedes mosquitoes. Symptoms can range from asymptomatic fever to life-threatening complications such as haemorrhagic fever and shock (1). Dengue fever is recognized by the (WHO (World Health Organization)) World Health Organization as a serious global public health threat in tropical and subtropical countries. Dengue-endemic regions are home to 2.5 billion people, and 400 million infections occur each year, with mortality rates exceeding 20% in some areas (2). Extremely heavy rains have lately devastated Pakistan, with its most populous metropolis of Karachi witnessing the worst floods in a century. Flooding and inadequate water sanitation have increased the risk of dengue, malaria, and other water-borne disease outbreaks. Determining whether dengue infection during pregnancy is associated with adverse effects on the fetus is important, given that women of reproductive age in dengue-endemic areas are at risk of contracting the disease. Studies have suggested an association between maternal infection during pregnancy and preterm birth, low birth weight, small gestational age births, stillbirth, and miscarriage (3, 4). According to Pouliot SH, et al., high rates of cesarean deliveries (44%) and pre-eclampsia (12%) occurred in women who had dengue infection during pregnancy (5). Even though there are several variants of dengue infection, the study found that the proportion of DENV-4 in pregnant women was higher than in non-pregnant women (6), the reason for which is still unclear. The gestational period involves various anatomical and physiological changes in the female body, such as increased capillary permeability, hemodilution, leukocytosis, thrombocytopenia, etc., which may complicate the assessment of the clinical manifestation of dengue due to opposing effects on the body, such as the contradicting leucocyte concentration, as pregnancy causes leukocytosis, whereas dengue causes leukopenia (6). Though the exact mechanism of the effect of maternal dengue on the fetus is yet to be determined, recent studies have put forward two mechanisms for fetal and neonatal morbidity caused by maternal dengue infection. The first theory is that dengue infection causes hemodynamic changes during pregnancy that could affect the placenta and cause fetal hypoxia, In contrast, the second theory states that dengue infection affects the fetus directly (7). ---Continue

Role of pre-existing immunity in driving the dengue virus serotype 2 genotype shift in the Philippines: A retrospective analysis of serological data

ObjectiveThe invasion of dengue virus (DENV)-2 Cosmopolitan genotype into the Philippines, where the Asian II genotype previously circulated challenges the principle of dengue serotype-specific immunity. Assessment of antibodies in this population may provide a mechanistic basis for how new genotypes emerge in dengue-endemic areas. MethodsWe evaluated the neutralizing antibody (nAb) and antibody-dependent enhancement (ADE) responses against the two genotypes using archived serum samples collected from 333 patients with confirmed dengue in Metro Manila, Philippines, before, during, and after the introduction of the Cosmopolitan genotype. We quantified nAb titers in baby hamster kidney (BHK-21) cells with or without the Fcγ receptor IIA (FcγRIIA) to detect the capacity of virus-antibody complexes to neutralize or enhance DENV. ResultsThe nAb potency of the archived serum samples against the two genotypes was greatly affected by the presence of FcγRIIA. We found significant differences in nAb titers between the two genotypes in BHK-21 cells with FcγRIIA (P <0.0001). The archived serum samples were incapable of fully neutralizing the Cosmopolitan genotype, but instead strongly promoted its ADE compared to the Asian II genotype (P <0.0001). ConclusionThese results reinforce the role of pre-existing immunity in driving genotype shifts. Our finding that specific genotypes exhibit differing susceptibilities to ADE by cross-reactive antibodies may have implications for dengue vaccine development.

Spatial analysis for risk assessment of dengue in Spain

IntroductionThe establishment of Aedes albopictus in new areas in Europe has changed the risk of local dengue transmission represented by imported human cases. The risk of transmission is determined by the distribution of travelers arriving from dengue-endemic areas and the distribution of Ae. albopictus as potential vectors of dengue in Spain. MethodsEnvironmental, entomological, epidemiological, demographic, tourism and travel data were analyzed to produce a series of maps to represent: the distribution of Ae. albopictus across municipalities; the risk of expansion of Ae. albopictus based on a species distribution model; the calculated index of travelers from dengue-endemic areas (IDVZE) per province; the percentage contribution of each municipality to the total number of cases in Spain. The maps were then added using map algebra, to profile the spatial risk of autochthonous dengue in Spain at a municipal level from 2016 to 2018. ResultsAe. albopictus was detected in 983 municipalities. The calculated IDVZE varied from 0.23 to 10.38, with the highest IDVZE observed in Madrid. The overall risk of autochthonous cases oscillated between 0.234 and 115, with the very high risk and high risk areas detected in the Mediterranean region, mainly in the Levantine coast and some parts of the Balearic Islands. Most of the interior of the peninsula was characterized as low risk. ConclusionPrevention and control measures to mitigate the risk of autochthonous dengue should be prioritized for municipalities in the high risk areas integrating early detection of imported dengue cases and vector control.