Co-circulation and co-infections of all dengue virus serotypes in Hyderabad, India 2014

Dengue virus serotype did not contribute to clinical severity or mortality in Taiwan's largest dengue outbreak in 2015

BACKGROUND

Dengue virus serotype 2 (DENV-2) was the major serotype in the 2015 dengue outbreak in Taiwan, while DENV-1 and DENV-3 were dominant between 2005 and 2014. We aimed to investigate whether DENV-2 contributed to disease severity and mortality in the outbreak in Kaohsiung city, Taiwan.

METHODS

We collected serum samples from dengue patients to detect the presence of DENV and determine the serotypes by using quantitative reverse transcription-polymerase chain reaction. Our cohorts comprised 105 DENV-1-infected cases and 1,550 DENV-2-infected cases. Demographic data, DENV serotype, and comorbidities were covariates for univariate and multivariate analyses to explore the association with severity and mortality.

RESULTS

The results suggested that DENV-1 persisted and circulated, while DENV-2 was dominant during the dengue outbreak that occurred between September and December 2015. However, DENV-2 did not directly contribute to either severity or mortality. Aged patients and patients with diabetes mellitus (DM) or moderate to severe chronic kidney disease (CKD) had a higher risk of developing severe dengue. The mortality of dengue patients was related to a higher Charlson comorbidity index score and severe dengue. Among DENV-2-infected patients and older patients, preexisting anti-dengue IgG, DM, and moderate to severe CKD were associated with severe dengue. Moreover, female sex and severe dengue were associated with a significantly higher risk of death.

CONCLUSIONS

Our findings highlight the importance of timely serological testing in elderly patients to identify potential secondary infections and focus on the meticulous management of elderly patients with DM or moderate to severe CKD to reduce dengue-related death.

Differential localization of dengue virus protease affects cell homeostasis and triggers to thrombocytopenia

Thrombocytopenia is one of the symptoms of many virus infections which is the "hallmark" in the case of dengue virus. In this study, we show the differential localization of existing two forms of dengue virus protease, i.e., NS2BNS3 to the nucleus and NS3 to the nucleus and mitochondria. We also report a nuclear transcription factor, erythroid differentiation regulatory factor 1 (EDRF1), as the substrate for this protease. EDRF1 regulates the expression and activity of GATA1, which in turn controls spectrin synthesis. Both GATA1 and spectrins are required for platelet formation. On the other hand, we found that the mitochondrial activities will be damaged by NS3 localization which cleaves GrpEL1, a co-chaperone of mitochondrial Hsp70. Levels of both EDRF1 and GrpEL1 were found to deteriorate in dengue virus-infected clinical samples. Hence, we conclude that NS2BNS3-mediated EDRF1 cleavage and the NS3-led mitochondrial dysfunction account for thrombocytopenia.

Association of Dengue Virus Serotypes 1&2 with Severe Dengue Having Deletions in Their 3′Untranslated Regions (3′UTRs)

Dengue virus infections are recorded as hyper-endemic in many countries, including India. Research pertaining to the reasons for frequent outbreaks and severe dengue is ongoing. Hyderabad city, India, has been recorded as a ‘hotspot’ for dengue virus infections. Dengue virus strains circulating over the past few years in Hyderabad city have been characterized at the molecular level to analyze the serotype/genotypes; 3′UTRs were further amplified and sequenced. The disease severity in patients infected with dengue virus strains with complete and 3′UTR deletion mutants was analyzed. Genotype I of the serotype 1 replaced genotype III, which has been circulating over the past few years in this region. Coincidentally, the number of dengue virus infections significantly increased in this region during the study period. Nucleotide sequence analysis suggested twenty-two and eight nucleotide deletions in the 3′UTR of DENV-1. The eight nucleotide deletions observed in the case of DENV-1 3′UTR were the first reported in this instance. A 50 nucleotide deletion was identified in the case of the serotype DENV-2. Importantly, these deletion mutants were found to cause severe dengue, even though they were found to be replication incompetent. This study emphasized the role of dengue virus 3′UTRs on severe dengue and emerging outbreaks.

Co-circulation of all the four Dengue virus serotypes during 2018-2019: first report from Eastern Uttar Pradesh, India

Dengue fever is an endemic disease in India, transmitted by an infected mosquito bite. In India, the number of concurrent infections and the circulation of multiple dengue virus (DENV) serotypes has increased in recent decades. Molecular surveillance among the DENV serotype is important to keep track of the circulating serotypes, evolutionary changes, and key mutations that can alter the diagnostics. The current study included patients admitted for dengue in the Eastern Uttar Pradesh (E-UP) region during 2018-2019. The genetic characterization of the circulating DENV was accomplished through partial CprM (511 bp) gene amplification via reverse transcriptase polymerase chain reaction and sequencing. Phylogenetic analysis revealed the circulation of all four DENV1-4 serotypes. DENV-2 was the most abundant serotype (44%, 27/61), followed by DENV-3 (32%, 20/61). DENV-1 had a 16% (10/61) predominance, while DENV-4 (6%, 4/61) was found to be the least abundant serotype. DENV-2 genotypes were distributed among lineages I (7.4%), II (85%) and III (7.4%) of genotype IV, DENV-3 to lineage III of genotype III, DENV-1 to genotype III; DENV-2 to lineage B (75%) and C (25%) of genotype I. This primary report on the co-circulation of DENV1-4 serotypes from the E-UP region highlights the requirement of continuous molecular surveillance for monitoring circulating DENV serotypes.

Genetic characterization of dengue virus from patients presenting multi-serotypic infections in the Northern West Bengal, India

Northern West Bengal, popularly known as North Bengal, is a dengue-endemic area, which has been severely affected by Dengue in the past few years resulting in massive hospitalizations and deaths. Genetic characterization of the circulating endemic dengue virus (DENV) serotypes is of paramount importance for the epidemiological understanding of the infection and subsequent vaccine development. The present study was conceived to characterize circulating dengue serotypes and to undertake phylogenetic study. EDTA blood samples of all (N = 83) NS1-positive cases of patients with acute febrile illness referred to different health care facilities were collected and processed for RNA isolation followed by the complementary DNA (cDNA) preparation. Serotype determination of dengue infection was done using conventional PCR by targeting the viral C-prM region. Phylogenetic tree was constructed by implementing the Maximum likelihood method. Out of 83 blood samples 17 were detected to be positive for the presence of dengue viral RNA. DENV3 was found to be the predominant serotype in the single-infection cases; however, we have detected multi-serotypic co-infections throughout the study. Joint pain was found to be the most valuable symptom for the prognosis of dengue. Sequence analyses suggested that both DENV1- and DENV3-circulating genotypes are in the genotype III group and remain closely related to the Indian clade. To the best of our knowledge, this is the first report on the genetic characterization of circulating DENVs in North Bengal, which may contribute to the study of dengue epidemic and pathogenesis.

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.

Molecular Characterization and Identification of Potential Inhibitors for 'E' Protein of Dengue Virus

Dengue is an arthropod-borne acute febrile illness caused by Dengue Virus (DENV), a member of Flaviviridae. Severity of the infection ranges from mild self-limiting illness to severe life-threatening hemorrhagic fever (DHF) and dengue shock syndrome (DSS). To date, there is no specific antiviral therapy established to treat the infection. The current study reports the epidemiology of DENV infections and potential inhibitors of DENV 'E' protein. Among the various serotypes, DENV-2 serotype was observed more frequently, followed by DENV-4, DENV-1, and DENV-3. New variants of existing genotypes were observed in DENV-1, 2, and 4 serotypes. Predominantly, the severe form of dengue was attributable to DENV-2 infections, and the incidence was more common in males and pediatric populations. Both the incidence and the disease severity were more common among the residents of non-urban environments. Due to the predominantly self-limiting nature of primary dengue infection and folk medicine practices of non-urban populations, we observed a greater number of secondary dengue cases than primary dengue cases. Hemorrhagic manifestations were more in secondary dengue in particularly in the pediatric group. Through different computational methods, ligands RGBLD1, RGBLD2, RGBLD3, and RGBLD4 are proposed as potential inhibitors in silico against DENV-1, -2, -3, and -4 serotypes.

Development of Novel Dengue NS1 Multiplex Lateral Flow Immunoassay to Differentiate Serotypes in Serum of Acute Phase Patients and Infected Mosquitoes

Dengue is among the most rapidly spreading arboviral disease in the world. A low-cost, easy to use point-of-care diagnostic tool for the detection and differentiation of dengue virus serotypes could improve clinical management, disease prevention, epidemiological surveillance, and outbreak monitoring, particularly in regions where multiple serotypes co-circulate. Despite widespread deployment, no commercial dengue antigen diagnostic test has proven effective in differentiating among dengue virus serotypes. In the current study, we first established mAb pairs and developed a multiplex lateral flow immunoassay for the simultaneous detection of the dengue viral NS1 antigen and identification of serotype. The proposed system, called Dengue serotype NS1 Multiplex LFIA, provides high sensitivity and specificity. In testing for JEV, ZIKV, YFV, WNV, and CHIKV, the multiplex LFIA gave no indication of cross- reactivity with cell culture supernatants of other flaviviruses or chikungunya virus. In analyzing 187 samples from patients suspected of dengue infection, the detection sensitivity for serotype D1 to D4 was 90.0%, 88.24%, 82.61%, and 83.33% and serotype specificity was 98.74%, 96.13%, 99.39%, and 97.04%, respectively. Our multiplex LFIA can also identify mono- and co-infection of different serotype of dengue viruses in mosquitoes. The proposed Multiplex LFIA provides a simple tool for the rapid detection of dengue serotypes and in the differential diagnosis of fever patients in regions where medical resources are limited and/or multiple DENVs co-circulate.

Towards Integrated Management of Dengue in Mumbai

With increasing urbanisation, the dengue disease burden is on the rise in India, especially in large cities such as Mumbai. Current dengue surveillance in Mumbai includes municipal corporation carrying out specific activities to reduce mosquito breeding sites and the use of insecticides to suppress the adult mosquito populations. Clinical cases remain either underreported or misreported due to the restriction to government clinics, missing the large private health care sector. There is a need for an integrated approach to manage dengue outbreaks in Mumbai. There are various novel strategies available for use that can be utilised to improve disease detection, mosquito surveillance, and control of mosquito-borne diseases. These novel technologies are discussed in this manuscript. Given the complex ecosystem of mosquito-borne diseases in Mumbai, integrating data obtained from these technologies would support the ongoing mosquito control measures in Mumbai.

Flavivirus: From Structure to Therapeutics Development

Flaviviruses are still a hidden threat to global human safety, as we are reminded by recent reports of dengue virus infections in Singapore and African-lineage-like Zika virus infections in Brazil. Therapeutic drugs or vaccines for flavivirus infections are in urgent need but are not well developed. The Flaviviridae family comprises a large group of enveloped viruses with a single-strand RNA genome of positive polarity. The genome of flavivirus encodes ten proteins, and each of them plays a different and important role in viral infection. In this review, we briefly summarized the major information of flavivirus and further introduced some strategies for the design and development of vaccines and anti-flavivirus compound drugs based on the structure of the viral proteins. There is no doubt that in the past few years, studies of antiviral drugs have achieved solid progress based on better understanding of the flavivirus biology. However, currently, there are no fully effective antiviral drugs or vaccines for most flaviviruses. We hope that this review may provide useful information for future development of anti-flavivirus drugs and vaccines.

A novel anti-NS2BNS3pro antibody-based indirect ELISA test for the diagnosis of dengue virus infections

Dengue virus reportedly circulates as four genetically distinct serotypes for which there is no widely accepted vaccine or drug at present. Morbidity and mortality caused by this virus are alarming for the possible increased threat to human health. A suitable diagnostic test is the prerequisite for designing and developing control measures. But, the tests being employed at present possess one or the other drawback for this disease diagnosis. During the dengue virus infections, NS2B is essential for the stability and catalytic activity of the NS3 protease. N-terminal 185 amino acids of NS3 protease domain along with hydrophilic portion of NS2B (NS2BNS3pro) is being used to screen dengue inhibitors but not for diagnosis until now. In the present study, we have used purified NS2BNS3pro as an antigen to trap anti-NS2BNS3pro antibodies of the clinical samples. Antibodies were detected successfully in both Western blot analysis and enzyme-linked immunosorbent assay (ELISA) tests. In ELISA, antibodies were detected in both primary and secondary infections of all serotypes. Interestingly, 17 samples declared as other febrile infections by NS1 and IgM/IgG tests were found to be positive in present test, which were further confirmed by reverse-transcription polymerase chain reaction. In silico studies suggested the absence of conserved epitopes between NS2BNS3pro and the counterpart in JEV, Zika, and CHIKV, indicating less possibility of crossreaction, which was in turn confirmed by using synthetic peptides representing the above epitopes. Statistical analysis with 76% specificity, 87% sensitivity, and 95% concordance also supported the present test as a suitable test for large scale diagnosis of dengue virus infections.

Molecular investigation of the dengue outbreak in Karnataka, South India, reveals co-circulation of all four dengue virus serotypes

The growing incidence of dengue outbreaks in the state of Karnataka prompted us to study the circulating dengue virus (DENV) and their proportion among the suspected cases of dengue patients during the disease outbreak at Mysuru district of Southern India. The presence of the DENV in a patient's serum sample was identified by RT-PCR using previously published primer pairs targeting CprM gene. DENV serotyping was carried out by semi-nested multiplex PCR using serotype-specific primers and nucleotide sequencing. Three hundred fifty-five samples of serum from suspected dengue cases were collected, and 203 samples (57.18%) were found positives. In 2016, DENV-4 (97.87%) was found to be the most dominant DENV serotype either alone or as co-infection, followed by DENV-2 (8.51%) and DENV-3 (4.25%). In 47 positive cases, co-infection with more than one serotype was detected in 4 cases (8.51%). The analysis of the dengue cases in 2017, DENV-4 was dominating serotype (33.97%), followed by the emergence of DENV-2 (32.05%), DENV-3 (25.64%), and DENV-1 (25.00%). Our study also reports the circulation of all four DENV serotypes in the Mysuru district of Southern India, with concurrent infections rate of 16.66% in 2017. The present study provides information regarding the genetic variation among the circulating DENV serotype in an Indian state of Karnataka. The need for the studying genetic diversity of DENV will be useful during the continuous monitoring for disease burden as well as the development of appropriate prophylactic measures to control the spread of dengue infection.

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

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

Circulation of dengue virus serotypes in hyperendemic region of New Delhi, India during 2011-2017

BACKGROUND

Dengue fever has become a hampering menace in New Delhi India, since the disease has become hyperendemic, due to circulation of multiple serotypes of dengue virus (DENV). This hyperendemicity poses a greater risk of secondary infections in human health system. This is a major issue which leads to apprehension amongst the researchers and health organizations and thus requires regular epidemiological surveillance.

METHODS

We analyzed the prevalence and serotypic distribution of dengue fever cases reported from the Southern part of New Delhi during continued surveillance from 2011 to 2017. The blood samples for the investigation were obtained from the patients suspected with dengue fever attending the OPD at a local Health Centre. The data for 2011-2016 was already published from our laboratory. The samples collected during 2017 were serotyped and characterized in the present study.

RESULTS

A total of 565 samples (59%) were positive for DENV of 958 samples tested by RT-PCR during 7 years (2011-2017). Our study has shown that most infections were caused by DENV-2 during 2011-2015. The data has shown occurrence of all four serotypes of DENV during 2015 and predominance of DENV-3 in 2016 and 2017. Further, predominant combination of DENV-1 and DENV-2 was found in most of the co-infections. To the best of our knowledge this is the first study showing the epidemiological trend of dengue fever in reference to the circulating DENV serotypes and co-infections from a hyperendemic region of New Delhi during 2011-2017.

CONCLUSIONS

This hyperendemic pattern of DENV and instantaneous shift in circulation of its serotypes is likely pose a greater risk of secondary infections. Inclusion of comprehensive community and hospital surveillance of dengue fever will assist in formulation and implementation of effective control measures.

Mitochondrial Import of Dengue Virus NS3 Protease and Cleavage of GrpEL1, a Cochaperone of Mitochondrial Hsp70

Dengue virus infections, which have been reported in nearly 140 countries, pose a significant threat to human health. The genome of dengue virus encodes three structural and seven nonstructural (NS) proteins along with two untranslated regions, one each on both ends. Among them, dengue protease (NS3) plays a pivotal role in polyprotein processing and virus multiplication. NS3 is also known to regulate several host proteins to induce and maintain pathogenesis. Certain viral proteins are known to interact with mitochondrial membrane proteins and interfere with their functions, but the association of a virus-coded protein with the mitochondrial matrix is not known. In this report, by using in silico analysis, we show that NS3pro alone is capable of mitochondrial import; however, this is dependent on its innate mitochondrial transport signal (MTS). Transient-transfection and protein import studies confirm the import of NS3pro to the mitochondrial matrix. Similarly, NS3pro-helicase (amino acids 1 to 464 of NS3) also targets the mitochondria. Intriguingly, reduced levels of matrix-localized GrpE protein homolog 1 (GrpEL1), a cochaperone of mitochondrial Hsp70 (mtHsp70), were noticed in NS3pro-expressing, NS3pro-helicase-expressing, and virus-infected cells. Upon the use of purified components, GrpEL1 undergoes cleavage, and the cleavage sites have been mapped to KR⁸¹A and QR⁹²S. Importantly, GrpEL1 levels are seriously compromised in severe dengue virus-infected clinical samples. Our studies provide novel insights into the import of NS3 into host mitochondria and identify a hitherto unknown factor, GrpEL1, as a cleavage target, thereby providing new avenues for dengue virus research and the design of potential therapeutics.IMPORTANCE Approximately 40% of the world's population is at risk of dengue virus infection. There is currently no specific drug or potential vaccine for these infections. Lack of complete understanding of the pathogenesis of the virus is one of the hurdles that must be overcome in developing antivirals for this virus infection. In the present study, we observed that the dengue virus-coded protease imports to the mitochondrial matrix, and our report is the first ever of a virus-coded protein, either animal or human, importing to the mitochondrial matrix. Our analysis indicates that the observed mitochondrial import is due to an inherited mitochondrial transport signal. We also show that matrix-localized GrpE protein homolog 1 (GrpEL1), a cochaperone of mitochondrial Hsp70 (mtHsp70), is also the substrate of dengue virus protease, as observed in vitro and ex vivo in virus-infected cells and dengue virus-infected clinical samples. Hence, our studies reveal an essential aspect of the pathogenesis of dengue virus infections, which may aid in developing antidengue therapeutics.

Molecular diversity of dengue virus serotypes 1-4 during an outbreak of acute dengue virus infection in Theni, India

Background

Dengue fever (DF) is caused by an arthropod-borne dengue virus (DENV), has four serotypes and several genotypes. Although having clinical and epidemiological significance, the information on the circulating serotypes/genotypes is scarce in India.

Materials and Methods

Blood specimens were collected from the patients suspected of DF and they are tested for DENV NS1 antigen and DENV IgM by ELISA. Antigen-positive samples were further serotyped by reverse transcriptase polymerase chain reaction. Representative samples from each serotype were sequenced to identify the genotypes.

Results

All the four DENV serotypes were detected with the pre-dominance of DENV-1 (n = 49; 41.9%). Cases with multiple DENV serotype infections were also identified. Genotyping showed that DENV-1 belonging to genotype I, DENV-2 cosmopolitan (IV), DENV-3 genotype III and DENV-4 genotype I were active in the circulation during the outbreak in 2017.

Conclusion

Our study documents the molecular characteristics of DENV circulating in our geographical locality. The detection of heterologous DENV serotypes highlights the importance of regular molecular monitoring for the early recognition of any switch in pre-dominant serotype.

The Clinical Features of Co-circulating Dengue Viruses and the Absence of Dengue Hemorrhagic Fever in Pakistan

Dengue virus (DENV) is the most common and widespread arboviral infection worldwide. Though all four DENV serotypes cocirculate in nature, the clinicopathological framework of these serotypes is undefined in Pakistan. A cross-sectional, observational study was performed to document the circulation of various arboviruses in the Sindh region of Pakistan. Here we describe a population of patients diagnosed with DENV spanning a 2-year period. This study used an orthogonal system of NS1 antigen ELISA followed by RT-PCR for DENV detection and subtyping. A total of 168 NS1 positive patients were evaluated of which 91 patients were serotyped via RT-PCR. There was no significant difference between sex or age for infection risk and peak transmission occurred during the Autumn months. DENV2 was the most common serotype followed by DENV1 then DENV3, then DENV4. The data show that DENV1 patients were more likely to have abnormal liver function tests; DENV2 infected patients were more likely to exhibit arthralgia and neurological symptoms; DENV3 patients were more likely to complain of burning micturition and have elevated lymphocyte counts and low hematocrit; and DENV4 patients were more likely to report headaches and rash. Notably, no dengue hemorrhagic fever or other manifestations of severe dengue fever were present in patients with primary or secondary infections. We were able to identify significantly more NS1 antigen positive patients than RT-PCR. This study demonstrates that all four DENV serotypes are co-circulating and co-infecting in Pakistan.

A New High-Throughput Tool to Screen Mosquito-Borne Viruses in Zika Virus Endemic/Epidemic Areas

Mosquitoes are vectors of arboviruses affecting animal and human health. Arboviruses circulate primarily within an enzootic cycle and recurrent spillovers contribute to the emergence of human-adapted viruses able to initiate an urban cycle involving anthropophilic mosquitoes. The increasing volume of travel and trade offers multiple opportunities for arbovirus introduction in new regions. This scenario has been exemplified recently with the Zika pandemic. To incriminate a mosquito as vector of a pathogen, several criteria are required such as the detection of natural infections in mosquitoes. In this study, we used a high-throughput chip based on the BioMark™ Dynamic arrays system capable of detecting 64 arboviruses in a single experiment. A total of 17,958 mosquitoes collected in Zika-endemic/epidemic countries (Brazil, French Guiana, Guadeloupe, Suriname, Senegal, and Cambodia) were analyzed. Here we show that this new tool can detect endemic and epidemic viruses in different mosquito species in an epidemic context. Thus, this fast and low-cost method can be suggested as a novel epidemiological surveillance tool to identify circulating arboviruses.

Geographical distribution of primary & secondary dengue cases in India - 2017: A cross-sectional multicentric study

Background & objectives

Dengue virus infection is endemic in India with all the four serotypes of dengue virus in circulation. This study was aimed to determine the geographic distribution of the primary and secondary dengue cases in India.

Methods

A multicentre cross-sectional study was conducted at Department of Health Research / Indian Council of Medical Research (DHR)/(ICMR) viral research and diagnostic laboratories (VRDLs) and selected ICMR institutes located in India. Only laboratory-confirmed dengue cases with date of onset of illness less than or equal to seven days were included between September and October 2017. Dengue NS1 antigen ELISA and anti-dengue IgM capture ELISA were used to diagnose dengue cases while anti-dengue IgG capture ELISA was used for identifying the secondary dengue cases.

Results

Of the 1372 dengue cases, 897 (65%) were classified as primary dengue and 475 (35%) as secondary dengue cases. However, the proportion varied widely geographically, with Theni, Tamil Nadu; Tirupati, Andhra Pradesh and Udupi-Manipal, Karnataka reporting more than 65 per cent secondary dengue cases while Srinagar, Jammu and Kashmir reporting as low as 10 per cent of the same. The median age of primary dengue cases was 25 yr [interquartile range (IQR 17-35] while that of secondary dengue cases was 23 yr (IQR 13.5-34). Secondary dengue was around 50 per cent among the children belonging to the age group 6-10 yr while it ranged between 20-43 per cent among other age groups.

Interpretation & conclusions

Our findings showed a wide geographical variation in the distribution of primary and secondary dengue cases in India. It would prove beneficial to include primary and secondary dengue differentiation protocol in the national dengue surveillance programme.

Emergence of dengue virus 4 as the predominant serotype during the outbreak of 2017 in South India

Context

Dengue virus (DENV) causes acute febrile illness in tropical and subtropical countries. In India there is a steady increase in incidence since 1950s which could be attributed to emergence of new serotype or lineage\clade shifts in circulating DENV.

Aims

We aimed to perform molecular characterisation and phylogenetic analysis on samples from the recent outbreak (August-October 2017).

Settings and Design

Retrospective epidemiological analysis of dengue outbreak.

Subjects and Methods

Samples positive for non-steroidal 1 antigen by enzyme-linked immunosorbent assay (n = 147) were included. The study was approved by our institute ethics committee (JIP/IEC/2018/496). Five hundred and eleven base pair of capsid and pre-membrane encoding genes (CprM) region was amplified using Lanciotti primers, followed by second round of polymerase chain reaction using serotype specific primers. Samples which were positive by second round (n = 68) were sequenced and genotyped using Basic Local Alignment Search Tool analysis and phylogenetic tree was constructed by MEGA7 software.

Results

Phylogenetic analysis of CprM sequences identified all 4 serotypes in circulation during this outbreak. We observed both single (n = 50) and concurrent infections (n = 18), with DENV4 as the major contributor (64%). Within Genotype I of DENV4 we observed a distinct new clade (Clade E) which was 2.6% ± 0.9%-5.5% ± 1.1% divergent from the other clades. Among the concurrent infection, DENV 4 and DENV 2 combination was observed to form the majority (77.8%).

Conclusions

Overall this study documents the emergence of DENV4 as the major serotype in circulation, replacing DENV1, 2 and 3 which had been previously reported from Tamil Nadu and Puducherry. This substantiates the need for continuous monitoring in endemic countries like India, where such data may impact the formulation of vaccine policy for dengue.

Pathogen blocking in Wolbachia-infected Aedes aegypti is not affected by Zika and dengue virus co-infection

Background

Wolbachia’s ability to restrict arbovirus transmission makes it a promising tool to combat mosquito-transmitted diseases. Wolbachia-infected Aedes aegypti are currently being released in locations such as Brazil, which regularly experience concurrent outbreaks of different arboviruses. A. aegypti can become co-infected with, and transmit multiple arboviruses with one bite, which can complicate patient diagnosis and treatment.

Methodology/principle findings

Using experimental oral infection of A. aegypti and then RT-qPCR, we examined ZIKV/DENV-1 and ZIKV/DENV-3 co-infection in Wolbachia-infected A. aegypti and observed that Wolbachia-infected mosquitoes experienced lower prevalence of infection and viral load than wildtype mosquitoes, even with an extra infecting virus. Critically, ZIKV/DENV co-infection had no significant impact on Wolbachia’s ability to reduce viral transmission. Wolbachia infection also strongly altered expression levels of key immune genes Defensin C and Transferrin 1, in a virus-dependent manner.

Conclusions/significance

Our results suggest that pathogen interference in Wolbachia-infected A. aegypti is not adversely affected by ZIKV/DENV co-infection, which suggests that Wolbachia-infected A. aegypti will likely prove suitable for controlling mosquito-borne diseases in environments with complex patterns of arbovirus transmission.

Wolbachia is an endosymbiotic bacterium that infects insects. It has been artificially transferred into Aedes aegypti, a mosquito species that can transmit medically important viruses including dengue, chikungunya, and Zika. Wolbachia in A. aegypti limits infection with these viruses, making the mosquitoes much less capable of transmitting them to people. In tropical areas, where these viral pathogens are commonly found, it is not unusual for outbreaks of different viruses to occur at the same time, which can complicate diagnosis and treatment for those afflicted. Mosquitoes with Wolbachia are currently being released into these areas to reduce transmission of these diseases. In our study, we assessed whether Wolbachia infection in A. aegypti mosquitoes could still effectively inhibit the dengue and Zika viruses if the mosquitoes were fed both viruses at the same time. We found that Wolbachia was still very effective at inhibiting the replication of both viruses in the mosquito, and likewise still greatly reduced the chance of transmission of either virus. Our results suggest that Wolbachia-infected mosquitoes should be able to limit infection with more than one virus, should they encounter them in the field.

Molecular epidemiology of dengue, yellow fever, Zika and Chikungunya arboviruses: An update

Arboviruses are a group of viruses transmitted by arthropods. They are characterized by a wide geographic distribution, which is associated with the presence of the vector, and cause asymptomatic infections or febrile diseases in humans in both enzootic and urban cycles. Recent reports of human infections caused by viruses such as dengue, Zika, and chikungunya have raised concern regarding public health, and have led to the re-evaluation of surveillance mechanisms and measures to control the transmission of these arboviruses. Viruses such as Mayaro and Usutu are not currently responsible for a high number of symptomatic infections in humans, but should remain under epidemiological surveillance to avoid the emergence of new epidemics, as happened with Zika virus, that are associated with new or more severe symptoms. Additionally, significant variation has been observed in these viruses, giving rise to different lineages. Until recently, the emergence of new lineages has primarily been related to geographical distribution and dispersion, allowing us to ascertain the possible origins and direction of expansion of each virus type, and to make predictions regarding regions where active infections in humans are likely to occur. Therefore, this review is focused on untangling the molecular epidemiology of Dengue, Yellow fever, Zika and Chikungunya due to their recent epidemics in Latinamerica but provides an update on the geographical distribution globally of these viral variants, and outlines the need for further understanding of the genotypes/lineages assignment.

Co-circulation of four dengue serotypes at South Eastern Andhra Pradesh, India: A prospective study

Background

Dengue is one of the most important mosquito-borne viral diseases in the world. The emergence and spread of four dengue viruses (DENVs) (serotypes) represent a global pandemic. The four distinct serotypes are, namely, DENV-1, DENV-2, DENV-3 and DENV-4. Very few dengue serotyping studies have been reported from Andhra Pradesh. In this context, the present study focuses on the circulating serotypes of dengue in South-Eastern Andhra Pradesh.

Methodology

Study was done at Sri Venkateswara Institute of Medical Sciences, a teaching hospital in Tirupati, Andhra Pradesh. Acute phase dengue serum samples were collected and tested for NS1 antigen and anti-human IgM antibodies by enzyme-linked immunosorbent assay (ELISA). NS1-positive samples were further serotyped by reverse transcriptase real-time polymerase chain reaction (rRT-PCR).

Results

A total of 398 serum samples were received from clinically suspected dengue fever cases. Of these, 150 (37.7%) samples were positive for NS1 and/or IgM ELISA. The 96 NS1 antigen-positive samples were further processed for serotyping, of which 36 were negative by rRT-PCR. DENV-2 (41%) was the predominant serotype, followed by DENV-4 (37%), DENV-3 (12%) and DENV-1 (10%) in descending order.

Conclusion

This study reports the all four dengue serotypes' co-circulation. This is the first report from South Eastern Andhra Pradesh. Amongst four, DENV-2 was predominant followed by DENV-4. The information of predominant serotypes can guide in forecasting dengue outbreaks and improving control measures of vectors thus may be helpful in the prevention of outbreaks.

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

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