Epidemiology of Chikungunya in the Americas

Host-adaptive mutations in Chikungunya virus genome

Chikungunya virus (CHIKV) is the causative agent of chikungunya fever (CHIKF), and its primary vectors are the mosquitoes Aedes aegypti and Aedes albopictus. CHIKV was initially endemic to Africa but has spread globally in recent years and affected millions of people. According to a risk assessment by the World Health Organization, CHIKV has the potential seriously impact public health. A growing body of research suggests that mutations in the CHIKV gene that enhance viral fitness in the host are contributing to the expansion of the global CHIKF epidemic. In this article, we review the host-adapted gene mutations in CHIKV under natural evolution and laboratory transmission conditions, which can help improve our understanding of the adaptive evolution of CHIKV and provide a basis for monitoring and early warning of future CHIKV outbreaks.

Exploring the antiviral activities of the FDA-approved drug sulfadoxine and its derivatives against Chikungunya virus

BACKGROUND

Currently, there is no antiviral licensed to treat chikungunya fever, a disease caused by the infection with Alphavirus chikungunya (CHIKV). Treatment is based on analgesic and anti-inflammatory drugs to relieve symptoms. Our study aimed to evaluate the antiviral activity of sulfadoxine (SFX), an FDA-approved drug, and its derivatives complexed with silver(I) (AgSFX), salicylaldehyde Schiff base (SFX-SL), and with both Ag and SL (AgSFX-SL) against CHIKV.

METHODS

The anti-CHIKV activity of SFX and its derivatives was investigated using BHK-21 cells infected with CHIKV-nanoluc, a marker virus-carrying nanoluciferase reporter. Dose-response and time of drug-addition assays were performed in order to assess the antiviral effects of the compounds, as well as in silico data and ATR-FTIR analysis for insights on their mechanisms of action.

RESULTS

The SFX inhibited 34% of CHIKV replication, while AgSFX, SFX-SL, and AgSFX-SL enhanced anti-CHIKV activity to 84%, 89%, and 95%, respectively. AgSFX, SFX-SL, and AgSFX-SL significantly decreased viral entry and post-entry to host cells, and the latter also protected cells against infection. Additionally, molecular docking calculations and ATR-FTIR analysis demonstrated interactions of SFX-SL, AgSFX, and AgSFX-SL with CHIKV.

CONCLUSIONS

Collectively, our findings suggest that the addition of metal ions and/or Schiff base to SFX improved its antiviral activity against CHIKV.

Displaying alphavirus physicochemical consensus antigens on immunogenic liposomes enhances antibody elicitation in mice

Cobalt-porphyrin phospholipid displays recombinant protein antigens on liposome surfaces via antigen polyhistidine-tag (His-tag), and when combined with monophosphorylated lipid A and QS-21 yields the "CPQ" vaccine adjuvant system. In this proof of principle study, CPQ was used to generate vaccine prototypes that elicited antibodies for two different alphaviruses (AV). Mice were immunized with computationally designed, His-tagged, physicochemical property consensus (PCPcon) protein antigens representing the variable B-domain of the envelope protein 2 (E2) from the serotype specific Venezuelan Equine Encephalitis Virus (VEEVcon) or a broad-spectrum AV-antigen termed EVCcon. The CPQ adjuvant enhanced the antigenicity of both proteins without eliciting detectable anti-His-tag antibodies. Antibodies elicited from mice immunized with antigens admixed with CPQ showed orders-of-magnitude higher levels of antigen-specific IgG compared to alternative control adjuvants. The ELISA results correlated with antiviral activity against VEEV strain TC83 and more weakly to Chikungunya virus 118/25. Thus, display of E.coli-produced His-tagged E2 protein segments on the surface of immunogenic liposomes elicits high levels of antigen-specific and AV neutralizing antibodies in mice with vaccination, while facilitating vaccine preparation and providing dose-sparing potential.

Vaccine value profile for Chikungunya

Chikungunya virus (CHIKV) a mosquito-borne alphavirus is the causative agent of Chikungunya (CHIK), a disease with low mortality but high acute and chronic morbidity resulting in a high overall burden of disease. After the acute disease phase, chronic disease including persistent arthralgia is very common, and can cause fatigue and pain that is severe enough to limit normal activities. On average, around 40% of people infected with CHIKV will develop chronic arthritis, which may last for months or years. Recommendations for protection from CHIKV focus on infection control through preventing mosquito proliferation. There is currently no licensed antiviral drug or vaccine against CHIKV. Therefore, one of the most important public health impacts of vaccination would be to decrease burden of disease and economic losses in areas impacted by the virus, and prevent or reduce chronic morbidity associated with CHIK. This benefit would particularly be seen in Low and Middle Income Countries (LMIC) and socio-economically deprived areas, as they are more likely to have more infections and more severe outcomes. This 'Vaccine Value Profile' (VVP) for CHIK is intended to provide a high-level, holistic assessment of the information and data that are currently available to inform the potential public health, economic and societal value of vaccines in the development pipeline and vaccine-like products.This VVP was developed by a working group of subject matter experts from academia, non-profit organizations, public private partnerships, and multi-lateral organizations. All contributors have extensive expertise on various elements of the CHIK VVP and collectively aimed to identify current research and knowledge gaps.The VVP was developed using only existing and publicly available information.

Epidemiological, virological and clinical characterization of a Dengue/Zika outbreak in the Caribbean region of Costa Rica 2017-2018

The increase in incidence and geographical expansion of viruses transmitted by the Aedes mosquitoes, such as dengue (DENV) and zika (ZIKV) in the Americas, represents a burden for healthcare systems in tropical and subtropical regions. These and other under-detected arboviruses co-circulate in Costa Rica, adding additional complexity to their management due to their shared epidemiological behavior and similarity of symptoms in early stages. Since diagnostics of febrile illness is mostly based on clinical symptoms alone, we gathered acute-phase serum and urine from 399 samples of acute dengue-like cases from two healthcare facilities of Costa Rica, during an outbreak of arboviruses from July 2017 to May 2018, and tested them using molecular and serological methods. The analyses showed that of the clinically presumptive arbovirus cases that were reported, only 39.4% (n=153) of the samples were confirmed positive by RT-PCR to be DENV (DENV (10.3%), CHIKV (0.2%), ZIKV (27.3%), or mixed infections (1.5%). RT-PCR for other alphaviruses and flaviviruses, and PCR for Leptospira sp were negative. Furthermore, to assess flavivirus positivity in post-acute patients, the negative sera were tested against Dengue-IgM. 20% of sera were found positive, confounding even more the definitive number of cases, and emphasizing the need of several distinct diagnostic tools for accurate diagnostics. Molecular characterization of the prM and E genes from isolated viruses revealed that the American/Asian genotype of DENV-2 and the Asian lineage of ZIKV were circulating during this outbreak. Two different clades of DENV-2 American/Asian genotype were identified to co-circulate in the same region and a difference in the platelet and leukocyte count was noted between people infected with each clade, suggesting a putative distinct virulence. Our study sheds light on the necessity for healthcare strategies in managing arbovirus outbreaks, emphasizing the importance of comprehensive molecular and serological diagnostic approaches, as well as molecular characterization. This approach aids in enhancing our understanding of the clinical and epidemiological aspects of arboviral diseases during outbreaks. Our research highlights the need to strengthen training programs for health professionals and the need to increase research-based on laboratory evidence for diagnostic accuracy, guidance, development and implementation of public health interventions and epidemiological surveillance.

Accurate Recapitulation of Chikungunya Virus Complete Coding Sequence Phylogeny Using Variable Genome Regions for Genomic Surveillance

Chikungunya virus (CHIKV) is transmitted by mosquito bites and causes chikungunya fever (CHIKF). CHIKV has a single-stranded RNA genome and belongs to a single serotype with three genotypes. The Asian lineage has recently emerged in the Western Hemisphere, likely due to travel-associated introduction. Genetic variation accumulates in the CHIKV genome as the virus replicates, creating new lineages. Whole genome sequencing is ideal for studying virus evolution and spread but is expensive and complex. This study investigated whether specific, highly variable regions of the CHIKV genome could recapitulate the phylogeny obtained with a complete coding sequence (CDS). Our results revealed that concatenated highly variable regions accurately reconstructed CHIKV phylogeny, exhibiting statistically indistinguishable branch lengths and tree confidence compared to CDS. In addition, these regions adequately inferred the evolutionary relationships among CHIKV isolates from the American outbreak with similar results to the CDS. This finding suggests that highly variable regions can effectively capture the evolutionary relationships among CHIKV isolates, offering a simpler approach for future studies. This approach could be particularly valuable for large-scale surveillance efforts.

Identification of RACK1 as a novel regulator of non-structural protein 4 of chikungunya virus

Chikungunya virus (CHIKV) is a neglected arthropod-borne and anthropogenic alphavirus. Over the past two decades, the CHIKV distribution has undergone significant changes worldwide, from the original tropics and subtropics regions to temperate regions, which has attracted global attention. However, the interactions between CHIKV and its host remain insufficiently understood, which dampens the need for the development of an anti-CHIKV strategy. In this study, on the basis of the optimal overexpression of non-structural protein 4 (nsP4), we explore host interactions of CHIKV nsP4 using mass spectrometry-based protein-protein interaction approaches. The results reveal that some cellular proteins that interact with nsP4 are enriched in the ubiquitin-proteasome pathway. Specifically, the scaffold protein receptor for activated C kinase 1 (RACK1) is identified as a novel host interactor and regulator of CHIKV nsP4. The inhibition of the interaction between RACK1 and nsP4 by harringtonolide results in the reduction of nsP4, which is caused by the promotion of degradation but not the inhibition of nsP4 translation. Furthermore, the decrease in nsP4 triggered by the RACK1 inhibitor can be reversed by the proteasome inhibitor MG132, suggesting that RACK1 can protect nsP4 from degradation through the ubiquitin-proteasome pathway. This study reveals a novel mechanism by which the host factor RACK1 regulates CHIKV nsP4, which could be a potential target for developing drugs against CHIKV.

A 44-Nucleotide Region in the Chikungunya Virus 3' UTR Dictates Viral Fitness in Disparate Host Cells

We previously reported that deletion of a 44-nucleotide element in the 3' untranslated region (UTR) of the Chikungunya virus (CHIKV) genome enhances the virulence of CHIKV infection in mice. Here, we find that while this 44-nucleotide deletion enhances CHIKV fitness in murine embryonic fibroblasts in a manner independent of the type I interferon response, the same mutation decreases viral fitness in C6/36 mosquito cells. Further, the fitness advantage conferred by the UTR deletion in mammalian cells is maintained in vivo in a mouse model of CHIKV dissemination. Finally, SHAPE-MaP analysis of the CHIKV 3' UTR revealed this 44-nucleotide element forms a distinctive two-stem-loop structure that is ablated in the mutant 3' UTR without altering additional 3' UTR RNA secondary structures.

Winged Threat on the Offensive: A Literature Review Due to the First Identification of Aedes japonicus in Poland

Genetic studies preceded by the observation of an unknown mosquito species in Mikołów (Poland) confirmed that it belongs to a new invasive species in Polish fauna, Aedes japonicus (Theobald, 1901), a known vector for numerous infectious diseases. Ae. japonicus is expanding its geographical presence, raising concerns about potential disease transmission given its vector competence for chikungunya virus, dengue virus, West Nile virus, and Zika virus. This first genetically confirmed identification of Ae. japonicus in Poland initiates a comprehensive review of the literature on Ae. japonicus, its biology and ecology, and the viral infections transmitted by this species. This paper also presents the circumstances of the observation of Ae. japonicus in Poland and a methodology for identifying this species.

Clinical and laboratory diagnosis of Mayaro virus (MAYV): Current status and opportunities for further development

The recent outbreaks related to Mayaro virus (MAYV) infection in the Americas have brought this neglected virus as a potential threat to global public health. Given the range of symptoms that can be associated with MAYV infection, it can be challenging to diagnose individuals based on clinical signs, especially in countries with simultaneous circulation of other mosquito-borne viruses, such as dengue virus (DENV) and chikungunya virus (CHIKV). With this challenge in mind, laboratory-based diagnosis assumes a critical role in the introduction of measures to help prevent virus dissemination and to adequately treat patients. In this review, we provide an overview of the clinical features reported in infected patients and currently available laboratory tools that are used for MAYV diagnosis, discussing their advances, advantages, and limitations to apply in the field. Moreover, we explore novel point-of-care (PoC) diagnostic platforms that can provide de-centralised diagnostics for use in areas with limited laboratory infrastructure.

Increasing transmission of dengue virus across ecologically diverse regions of Ecuador and associated risk factors

The distribution and intensity of viral diseases transmitted by Aedes aegypti mosquitoes, including dengue, have rapidly increased over the last century. Here, we study dengue virus (DENV) transmission across the ecologically and demographically distinct regions or Ecuador. We analyzed province-level age-stratified dengue incidence data from 2000-2019 using catalytic models to estimate the force of infection of DENV over eight decades. We found that provinces established endemic DENV transmission at different time periods. Coastal provinces with the largest and most connected cities had the earliest and highest increase in DENV transmission, starting around 1980 and continuing to the present. In contrast, remote and rural areas with reduced access, like the northern coast and the Amazon regions, experienced a rise in DENV transmission and endemicity only in the last 10 to 20 years. The newly introduced chikungunya and Zika viruses have age-specific distributions of hospital-seeking cases consistent with recent emergence across all provinces. To evaluate factors associated with geographic differences in DENV transmission potential, we modeled DENV vector risk using 11,693 Aedes aegypti presence points to the resolution of 1 hectare. In total, 56% of the population of Ecuador, including in provinces identified as having increasing DENV transmission in our models, live in areas with high risk of Aedes aegypti, with population size, trash collection, elevation, and access to water as important determinants. Our investigation serves as a case study of the changes driving the expansion of DENV and other arboviruses globally and suggest that control efforts should be expanded to semi-urban and rural areas and to historically isolated regions to counteract increasing dengue outbreaks.

Chikungunya Arthritis Treatment with Methotrexate and Dexamethasone: A Randomized, Double-blind, Placebo-controlled Trial

BACKGROUND

Chikungunya fever is a reemerging epidemic disease caused by a single-stranded RNA alphavirus transmitted throughout by Aedes mosquitoes. Chikungunya virus infection is a biphasic disease in which 72% to 95% of affected individuals manifest acute chikungunya fever. Following the acute phase, more than 40% of affected individuals develop arthritis, often lasting more than 3 months, referred to as chronic chikungunya arthritis, which frequently mimics rheumatoid arthritis.

OBJECTIVE

This study aimed to evaluate the efficacy and safety of treatment of chronic chikungunya arthritis with methotrexate and dexamethasone in a randomized, double-blind, placebo-controlled clinical trial.

METHODS

The patients were reassessed for treatment response by the DAS28-ESR, tender joint count and swollen joint count, Patient Global Assessment, and for secondary measures, including the Health Assessment Questionnaire Disability Index and Pain Visual Analog Scale.

RESULTS

Thirty-one subjects were randomized (placebo, n = 16; methotrexate, n = 15); 27 completed treatment and 4 discontinued during the 8-week blinded period. Among the participants, 96.8% were female, with mean ± SD age was 52.9 ± 13. The mean ± SD disease duration prior to treatment was 220.9 ± 51.2 days. At 8 weeks, methotrexate-treated subjects showed a greater numerical trend towards improvement, but there were no significant differences between methotrexate- dexamethasone group and dexamethasone (placebo) group.

CONCLUSION

In this relatively small cohort, all of whom received background dexamethasone, there was a greater numerical improvement trend in prespecified outcome measures, but methotrexate in combination with dexamethasone was not superior to dexamethasone in chronic chikungunya arthritis.

Insulin reduces the transmission potential of chikungunya virus and activates the toll pathway in Aedes aegypti mosquitoes

Chikungunya virus (CHIKV) is an alphavirus that has re-emerged globally over the last two decades and has the potential to become endemic in the United States due to the presence of competent mosquito vectors, Aedes aegypti and Aedes albopictus. CHIK disease is characterised by fever, rash, and joint pain, and causes chronic debilitating joint pain and swelling in >50% of infected individuals. Given the disease severity caused by CHIKV and the global presence of vectors to facilitate its spread, strategies to reduce viral transmission are desperately needed; however, the human biological factors driving CHIKV transmission are poorly understood. Towards that end, we have previously shown that mosquitoes fed on alphavirus-infected obese mice have reduced infection and transmission rates compared to those fed on infected lean mice despite similar viremia in lean and obese mice. One of the many host factors that increase in obese hosts is insulin, which was previously shown to impact the infection of mosquitoes by several flaviviruses. However, insulin's impact on alphavirus infection of live mosquitoes is unknown and whether insulin influences mosquito-borne virus transmission has not been tested. To test this, we exposed A. aegypti mosquitoes to bloodmeals with CHIKV in the presence or absence of physiologically relevant levels of insulin and found that insulin significantly lowered both infection and transmission rates. RNA sequencing analysis on mosquito midguts isolated at 1-day-post-infectious-bloodmeal (dpbm) showed enrichment in genes in the Toll immune pathway in the presence of insulin, which was validated by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). We then sought to determine if the Toll pathway plays a role in CHIKV infection of Ae. aegypti mosquitoes; therefore, we knocked down Myd88, a critical immune adaptor molecule for the Toll pathway, in live mosquitoes, and found increased CHIKV infection compared to the mock knockdown control group. Overall, these data demonstrate that insulin reduces CHIKV transmission by Ae. aegypti and activates the Toll pathway in mosquitoes, suggesting that conditions resulting in higher serum insulin concentrations may reduce alphavirus transmission. Finally, these studies suggest that strategies to activate insulin or Toll signalling in mosquitoes may be an effective control strategy against medically relevant alphaviruses.

Chikungunya in Zhejiang Province, Southeast China

Background

Chikungunya is emerging and reemerging word-widely in the past decades. It is non-endemic in Zhejiang Province, Southeast China. Aedes albopictus, one of major vectors of chikungunya, is widely-distribution in Zhejiang, and autochthonous transmission is possible after introducing chikungunya virus.

Methods

Retrospectively collected the epidemiological, clinical and genetic data of chikungunya and conducted the descriptive analysis and gene sequence analysis.

Results

From 2008 to 2022, 29 chikungunya cases, including 26 overseas imported and 3 local cases, were reported and no cases died of chikungunya. More than half of the imported cases (53.85%) were from Southeast Asia. Seasonal peak of the imported cases was noted between August and September, and 42.31% cases onset in those 2 months. Eight prefecture-level cities and 16 counties reported cases during the study period, with Jinghua (27.59%) and Hangzhou (24.14%) reporting the largest number of cases. The 3 local cases were all reported in Qujiang, Quzhou in 2017. For imported cases, the male-female gender ratio was 2.71:1, 20-30 years old cases (46.15%) and commercial service (42.31%) accounted for the highest proportion. Clinically, fever (100%), fatigue (94.44%), arthralgia (79.17%), headache (71.43%) and erythra (65.22%) were the most common reported symptoms. Eight whole-genome sequences were obtained and belonged to East/Central/South African (ECSA) or Asian genotype.

Conclusions

With the change of immigration policy, the surveillance of chikungunya should be strengthened and the ability of the case discovery and diagnosis should be improved in Zhejiang in the post-COVID-19 era.

Fitness costs in the presence and absence of insecticide use explains abundance of two common Aedes aegypti kdr resistance alleles found in the Americas

Aedes aegypti is the vector of viruses such as chikungunya, dengue, yellow fever and Zika that have a critical impact on human health. Control of adult mosquitoes is widely done using pyrethroids, but resistance has reduced the effectiveness of this class of insecticides. Resistance to pyrethroids in mosquitoes is commonly due to mutations in the voltage-gated sodium channel (Vgsc) gene (these mutations are known as knockdown resistance, kdr). In the Americas and the Caribbean, the most common kdr alleles are 410L+1016I+1534C and 1534C. In this study, we conducted a population cage experiment to evaluate changes in the allele and genotype frequencies of the 410L+1016I+1534C allele by crossing two congenic strains; one carrying the 410L+1016I+1534C and another with the 1534C allele. Changes in allele frequencies were measured over 10 generations in the absence of insecticide exposure. We also applied one cycle of selection with deltamethrin at F9 to evaluate the changes in allele and genotype frequencies. Our findings indicate that fitness costs were higher with the 410L+1016I+1534C allele, relative to the 1534C allele, in the absence of deltamethrin exposure, but that the 410L+1016I+1534C allele provides a stronger advantage when exposed to deltamethrin relative to the 1534C allele. Changes in genotype frequencies were not in Hardy-Weinberg equilibrium and could not be explained by drift. Our results suggest the diametrically opposed fitness costs in the presence and absence of insecticides is a reason for the variations in frequencies between the 410L+1016I+1534C and 1534C alleles in field populations.

Analysis and Bayesian estimation of a model for Chikungunya dynamics with relapse: An outbreak in Acapulco, Mexico

Chikungunya is a vector-borne viral disease transmitted by Aedes aegypti and Aedes albopictus mosquitoes. It does not have any specific treatment, and there is no vaccine. Recent epidemiological data have indicated that a relapse of the infection can occur within three months of the initial infection; however, until now, mathematical models for the spread of the disease have not considered this factor. We propose a mathematical model for the transmission of the Chikungunya virus that considers relapse. We calculated the basic reproductive number $ (R_0) $ of the disease by using the next-generation operator method. We proved the existence of a forward bifurcation. We determined the existence and the global stability of the equilibrium points by using the Lyapunov function method. We fitted the model to data from an outbreak in 2015 in Acapulco, Mexico to estimate the model parameters and $ R_0 $ with the Bayesian approach via a Hamiltonian Monte Carlo method. In the local sensitivity analysis, we found that the fraction of infected individuals who become asymptomatic has a strong impact on the basic reproductive number and makes some control measures insufficient. The impact of the fraction of infected individuals who become asymptomatic should be considered in Chikungunya control strategies.

New weapons against the disease vector Aedes aegypti: From natural products to nanoparticles

Despite the global burden of viral diseases transmitted by Aedes aegypti, there is a lack of effective means of prevention and treatment. Strategies for vector control include chemical and biological approaches such as organophosphates and Bacillus thuringiensis var. israelensis (Bti), among others. However, important concerns are associated, such as resistance in mosquito larvae and deleterious effects on non-target organisms. In this scenario, novel approaches against A. aegypti have been investigated, including natural products (e.g. vegetable oil and extracts) and nanostructured systems. This review focuses on potential strategies for fighting A. aegypti, highlighting plant-based materials and nanomaterials able to induce toxic effects on egg, larva, pupa and adult mosquitoes. Issues including aspects of conventional vector control strategies are presented, and finally new insights on development of eco-friendly nanoformulations against A. aegypti are discussed.

Global geotemporal distribution of chikungunya disease, 2011-2022

BACKGROUND

Chikungunya virus is a mosquito-borne alphavirus, transmitted by Aedes mosquitoes. Humans serve as the primary reservoir. Chikungunya infections typically appear with an abrupt onset of fever, rash, and severe joint pain. Some 40% of cases develop chronic rheumatologic complications that can persist months to years.

OBJECTIVES

To improve precision of risk characterization by analyzing cases of chikungunya by year and by country and depicting this geotemporal distribution in map form.

METHOD

Chikungunya case counts by year were compiled from national or regional health authorities from 2011 to 2022. These data were augmented by published reviews plus the Program for Monitoring Emerging Diseases (ProMED). Country-level distribution was categorized into four groups based on recency and magnitude. Data for India were mapped on a per-state basis.

RESULTS

The global map depicts distribution of chikungunya disease from 2011 through 2022. Most cases are reported in tropical and subtropical areas, but notable exceptions include the northern coast of the Mediterranean Sea. Countries of high recency and frequency include India, Brazil, Sudan, and Thailand. Countries with high frequency, but few cases reported in 2019-22 include many Latin American and Caribbean countries. Subnational foci are discussed in general and mapped for India. The range of Aedes mosquitoes is broader than the geography where chikungunya infection is typically diagnosed.

CONCLUSIONS

These maps help identify geographical regions where residents or travelers are at greatest risk of chikungunya. Once vaccines are licensed to help prevent chikungunya, maps like these can help guide future vaccine decision-making.

Equine Polyclonal Antibodies Prevent Acute Chikungunya Virus Infection in Mice

Chikungunya virus (CHIKV) is a mosquito-transmitted pathogen that causes chikungunya disease (CHIK); the disease is characterized by fever, muscle ache, rash, and arthralgia. This arthralgia can be debilitating and long-lasting, seriously impacting quality of life for years. Currently, there is no specific therapy available for CHIKV infection. We have developed a despeciated equine polyclonal antibody (CHIKV-EIG) treatment against CHIKV and evaluated its protective efficacy in mouse models of CHIKV infection. In immunocompromised (IFNAR^-/-) mice infected with CHIKV, daily treatment for five consecutive days with CHIKV-EIG administered at 100 mg/kg starting on the day of infection prevented mortality, reduced viremia, and improved clinical condition as measured by body weight loss. These beneficial effects were seen even when treatment was delayed to 1 day after infection. In immunocompetent mice, CHIKV-EIG treatment reduced virus induced arthritis (including footpad swelling), arthralgia-associated cytokines, viremia, and tissue virus loads in a dose-dependent fashion. Collectively, these results suggest that CHIKV-EIG is effective at preventing CHIK and could be a viable candidate for further development as a treatment for human disease.

Increasing transmission of dengue virus across ecologically diverse regions of Ecuador and associated risk factors

The distribution and intensity of viral diseases transmitted by Aedes aegypti mosquitoes, including dengue, have rapidly increased over the last century. Ecuador is an interesting country to study drivers of dengue virus (DENV) transmission given it has multiple ecologically and demographically distinct regions. Here, we analyze province-level age-stratified dengue prevalence data from 2000-2019 using catalytic models to estimate the force of infection of DENV over eight decades and across provinces in Ecuador. We found that provinces established endemic DENV transmission at different time periods. Coastal provinces with the largest and most connected cities had the earliest and highest increase in DENV transmission, starting around 1980 and continuing to the present. In contrast, remote and rural areas with reduced access, like the northern coast and the Amazon regions, experienced a rise in DENV transmission and endemicity only in the last 10 to 20 years. The newly introduced chikungunya and Zika viruses have distinct age-specific prevalence distributions consistent with recent emergence across all provinces. We evaluated factors to the resolution of 1 hectare associated with geographic differences in vector suitability and arbovirus disease in the last 10 years by modeling 11,693 A aegypti presence points and 73,550 arbovirus cases. In total, 56% of the population of Ecuador lives in areas with high risk of Aedes aegypti. Most suitable provinces had hotspots for arbovirus disease risk, with population size, elevation, sewage connection, trash collection, and access to water as important determinants. Our investigation serves as a case study of the changes driving the expansion of DENV and other arboviruses globally and suggest that control efforts should be expanded to semi-urban and rural areas and to historically isolated regions to counteract increasing dengue outbreaks.

Global transmission suitability maps for dengue virus transmitted by Aedes aegypti from 1981 to 2019

Mosquito-borne viruses increasingly threaten human populations due to accelerating changes in climate, human and mosquito migration, and land use practices. Over the last three decades, the global distribution of dengue has rapidly expanded, causing detrimental health and economic problems in many areas of the world. To develop effective disease control measures and plan for future epidemics, there is an urgent need to map the current and future transmission potential of dengue across both endemic and emerging areas. Expanding and applying Index P, a previously developed mosquito-borne viral suitability measure, we map the global climate-driven transmission potential of dengue virus transmitted by Aedes aegypti mosquitoes from 1981 to 2019. This database of dengue transmission suitability maps and an R package for Index P estimations are offered to the public health community as resources towards the identification of past, current and future transmission hotspots. These resources and the studies they facilitate can contribute to the planning of disease control and prevention strategies, especially in areas where surveillance is unreliable or non-existent.

Chikungunya: risks for travellers

RATIONALE FOR REVIEW

Chikungunya outbreaks continue to occur, with changing epidemiology. Awareness about chikungunya is low both among the at-risk travellers and healthcare professionals, which can result in underdiagnosis and underreporting. This review aims to improve awareness among healthcare professionals regarding the risks of chikungunya for travellers.

KEY FINDINGS

Chikungunya virus transmission to humans occurs mainly via daytime-active mosquitoes, Aedes aegypti and Aedes albopictus. The areas where these mosquitoes live is continuously expanding, partly due to climate changes. Chikungunya is characterized by an acute onset of fever with joint pain. These symptoms generally resolve within 1-3 weeks, but at least one-third of the patients suffer from debilitating rheumatologic symptoms for months to years. Large outbreaks in changing regions of the world since the turn of the 21st century (e.g. Caribbean, La Réunion; currently Brazil, India) have resulted in growing numbers of travellers importing chikungunya, mainly to Europe and North America. Viremic travellers with chikungunya infection have seeded chikungunya clusters (France, United States of America) and outbreaks (Italy in 2007 and 2017) in non-endemic countries where Ae. albopictus mosquitoes are present. Community preventive measures are important to prevent disease transmission by mosquitoes. Individual preventive options are limited to personal protection measures against mosquito bites, particularly the daytime-active mosquitos that transmit the chikungunya virus. Candidate vaccines are on the horizon and regulatory authorities will need to assess environmental and host risk factors for persistent sequelae, such as obesity, age (over 40 years) and history of arthritis or inflammatory rheumatologic disease to determine which populations should be targeted for these chikungunya vaccines.

CONCLUSIONS/RECOMMENDATIONS

Travellers planning to visit destinations with active CHIKV circulation should be advised about the risk for chikungunya, prevention strategies, the disease manifestations, possible chronic rheumatologic sequelae and, if symptomatic, seek medical evaluation and report potential exposures.

Dengue and chikungunya virus loads in the mosquito Aedes aegypti are determined by distinct genetic architectures

Aedes aegypti is the primary vector of the arboviruses dengue (DENV) and chikungunya (CHIKV). These viruses exhibit key differences in their vector interactions, the latter moving more quicky through the mosquito and triggering fewer standard antiviral pathways. As the global footprint of CHIKV continues to expand, we seek to better understand the mosquito's natural response to CHIKV-both to compare it to DENV:vector coevolutionary history and to identify potential targets in the mosquito for genetic modification. We used a modified full-sibling design to estimate the contribution of mosquito genetic variation to viral loads of both DENV and CHIKV. Heritabilities were significant, but higher for DENV (40%) than CHIKV (18%). Interestingly, there was no genetic correlation between DENV and CHIKV loads between siblings. These data suggest Ae. aegypti mosquitoes respond to the two viruses using distinct genetic mechanisms. We also examined genome-wide patterns of gene expression between High and Low CHIKV families representing the phenotypic extremes of viral load. Using RNAseq, we identified only two loci that consistently differentiated High and Low families: a long non-coding RNA that has been identified in mosquito screens post-infection and a distant member of a family of Salivary Gland Specific (SGS) genes. Interestingly, the latter gene is also associated with horizontal gene transfer between mosquitoes and the endosymbiotic bacterium Wolbachia. This work is the first to link the SGS gene to a mosquito phenotype. Understanding the molecular details of how this gene contributes to viral control in mosquitoes may, therefore, also shed light on its role in Wolbachia.

Dengue-chikungunya infection in the tertiary care hospital of northern India: Cross-sectional latent class cluster analysis in viral infection

Cases of dengue and chikungunya fever are escalating all over India. Both viruses share a common vector, the "Aedes" mosquito. Due to similar clinical symptoms, both the dengue (DENV) and chikungunya (CHIKV) virus can circulate as co-infection. There is very limited data available on dengue-chikungunya co-infection in Uttarakhand, India. The purpose of this study was to determine the seroprevalence of dengue and chikungunya virus infections, as well as their co-infection, in patients presenting with clinical symptoms. Serum samples of clinically suspected patients from the tertiary care hospital of Uttarakhand were collected, and Latent Class Cluster Analysis was performed for clinical profiling. ELISA was performed for DENV and CHIKV. 279 cases were enrolled, out of which 222 (79.5%) came positive for dengue NS1 Ag, 143 (51.2%) for dengue IgM, 98 (35.1%) for IgG followed by 16 (5.7%) of CHIKV IgM, and 4 (1.4%) were NS1 Ag with CHIKV IgM. Among the clinical features, fever (n = 270, 96.8%) was the most common symptom in all suspected dengue and chikungunya cases. Other symptoms like chills (n = 254, 91.0%), arthralgia (n = 241, 86.4%), and headache (n = 240, 86.0%) were present in a significant number. Results showed fewer odds of getting both DENV and CHIKV infection simultaneously, but the risk is still not negligible. This study explores the clinical presentation of the suspected dengue-chikungunya case. The increasing incidence of dengue and chikungunya and their co-infection necessitate the authorities' active surveillance of endemic regions and effective patient care management.

Infection with chikungunya virus confers heterotypic cross-neutralizing antibodies and memory B-cells against other arthritogenic alphaviruses predominantly through the B domain of the E2 glycoprotein

Infections with Chikungunya virus, a mosquito-borne alphavirus, cause an acute febrile syndrome often followed by chronic arthritis that persists for months to years post-infection. Neutralizing antibodies are the primary immune correlate of protection elicited by infection, and the major goal of vaccinations in development. Using convalescent blood samples collected from both endemic and non-endemic human subjects at multiple timepoints following suspected or confirmed chikungunya infection, we identified antibodies with broad neutralizing properties against other alphaviruses within the Semliki Forest complex. Cross-neutralization generally did not extend to the Venezuelan Equine Encephalitis virus (VEEV) complex, although some subjects had low levels of VEEV-neutralizing antibodies. This suggests that broadly neutralizing antibodies elicited following natural infection are largely complex restricted. In addition to serology, we also performed memory B-cell analysis, finding chikungunya-specific memory B-cells in all subjects in this study as remotely as 24 years post-infection. We functionally assessed the ability of memory B-cell derived antibodies to bind to chikungunya virus, and related Mayaro virus, as well as the highly conserved B domain of the E2 glycoprotein thought to contribute to cross-reactivity between related Old-World alphaviruses. To specifically assess the role of the E2 B domain in cross-neutralization, we depleted Mayaro and Chikungunya virus E2 B domain specific antibodies from convalescent sera, finding E2B depletion significantly decreases Mayaro virus specific cross-neutralizing antibody titers with no significant effect on chikungunya virus neutralization, indicating that the E2 B domain is a key target of cross-neutralizing and potentially cross-protective neutralizing antibodies.

Growth in chikungunya virus-related research in ASEAN and South Asian countries from 1967 to 2022 following disease emergence: a bibliometric and graphical analysis

BACKGROUND

ASEAN (Association of Southeast Asian Nations) is composed of ten Southeast Asian countries bound by socio-cultural ties that promote regional peace and stability. South Asia, located in the southern subregion of Asia, includes nine countries sharing similarities in geographical and ethno-cultural factors. Chikungunya is one of the most significant problems in Southeast and South Asian countries. Much of the current chikungunya epidemic in Southeast Asia is caused by the emergence of a virus strain that originated in Africa and spread to Southeast Asia. Meanwhile, in South Asia, three confirmed lineages are in circulation. Given the positive correlation between research activity and the improvement of the clinical framework of biomedical research, this article aimed to examine the growth of chikungunya virus-related research in ASEAN and South Asian countries.

METHODS

The Scopus database was used for this bibliometric analysis. The retrieved publications were subjected to a number of analyses, including those for the most prolific countries, journals, authors, institutions, and articles. Co-occurrence mapping of terms and keywords was used to determine the current state, emerging topics, and future prospects of chikungunya virus-related research. Bibliometrix and VOSviewer were used to analyze the data and visualize the collaboration network mapping.

RESULTS

The Scopus search engine identified 1280 chikungunya-related documents published by ASEAN and South Asian countries between 1967 and 2022. According to our findings, India was the most productive country in South Asia, and Thailand was the most productive country in Southeast Asia. In the early stages of the study, researchers investigated the vectors and outbreaks of the chikungunya virus. In recent years, the development of antivirus agents has emerged as a prominent topic.

CONCLUSIONS

Our study is the first to present the growth of chikungunya virus-related research in ASEAN and South Asian countries from 1967 to 2022. In this study, the evaluation of the comprehensive profile of research on chikungunya can serve as a guide for future studies. In addition, a bibliometric analysis may serve as a resource for healthcare policymakers.

Insights into the role of the cobalt(III)-thiosemicarbazone complex as a potential inhibitor of the Chikungunya virus nsP4

Chikungunya virus (CHIKV) is the causative agent of chikungunya fever, a disease that can result in disability. Until now, there is no antiviral treatment against CHIKV, demonstrating that there is a need for development of new drugs. Studies have shown that thiosemicarbazones and their metal complexes possess biological activities, and their synthesis is simple, clean, versatile, and results in high yields. Here, we evaluated the mechanism of action (MOA) of a cobalt(III) thiosemicarbazone complex named [CoIII(L1)2]Cl based on its in vitro potent antiviral activity against CHIKV previously evaluated (80% of inhibition on replication). Furthermore, the complex has no toxicity in healthy cells, as confirmed by infecting BHK-21 cells with CHIKV-nanoluciferase in the presence of the compound, showing that [CoIII(L1)2]Cl inhibited CHIKV infection with the selective index of 3.26. [CoIII(L1)2]Cl presented a post-entry effect on viral replication, emphasized by the strong interaction of [CoIII(L1)2]Cl with CHIKV non-structural protein 4 (nsP4) in the microscale thermophoresis assay, suggesting a potential mode of action of this compound against CHIKV. Moreover, in silico analyses by molecular docking demonstrated potential interaction of [CoIII(L1)2]Cl with nsP4 through hydrogen bonds, hydrophobic and electrostatic interactions. The evaluation of ADME-Tox properties showed that [CoIII(L1)2]Cl presents appropriate lipophilicity, good human intestinal absorption, and has no toxicological effect as irritant, mutagenic, reproductive, and tumorigenic side effects.

Expected endpoints from future chikungunya vaccine trial sites informed by serological data and modeling

In recent decades, there has been an increased interest in developing a vaccine for chikungunya. However, due to its unpredictable transmission, planning for a chikungunya vaccine trial is challenging. To inform decision making on the selection of sites for a vaccine efficacy trial, we developed a new framework for projecting the expected number of endpoint events at a given site. In this framework, we first accounted for population immunity using serological data collated from a systematic review and used it to estimate parameters related to the timing and size of past outbreaks, as predicted by an SIR transmission model. Then, we used that model to project the infection attack rate of a hypothetical future outbreak, in the event that one were to occur at the time of a future trial. This informed projections of how many endpoint events could be expected if a trial were to take place at that site. Our results suggest that some sites may have sufficient transmission potential and susceptibility to support future vaccine trials, in the event that an outbreak were to occur at those sites. In general, we conclude that sites that have experienced outbreaks within the past 10 years may be poorer targets for chikungunya vaccine efficacy trials in the near future. Our framework also generates projections of the numbers of endpoint events by age, which could inform study participant recruitment efforts.

Development and validation of a clinical rule for the diagnosis of chikungunya fever in a dengue-endemic area

Rio de Janeiro is a dengue-endemic city that experienced Zika and chikungunya epidemics between 2015 and 2019. Differential diagnosis is crucial for indicating adequate treatment and assessing prognosis and risk of death. This study aims to derive and validate a clinical rule for diagnosing chikungunya based on 3,214 suspected cases consecutively treated at primary and secondary health units of the sentinel surveillance system (up to 7 days from onset of symptoms) in Rio de Janeiro, Brazil. Of the total sample, 624 were chikungunya, 88 Zika, 51 dengue, and 2,451 were negative for all these arboviruses according to real-time polymerase chain reaction (RT-qPCR). The derived rule included fever (1 point), exanthema (1 point), myalgia (2 points), arthralgia or arthritis (2 points), and joint edema (2 points), providing an AUC (area under the receiver operator curve) = 0.695 (95% CI: 0.662-0.725). Scores of 4 points or more (validation sample) showed 74.3% sensitivity (69.0% - 79.2%) and 51.5% specificity (48.8% - 54.3%). Adding more symptoms improved the specificity at the expense of a lower sensitivity compared to definitions proposed by government agencies based on fever alone (European Center for Disease Control) or in combination with arthralgia (World Health Organization) or arthritis (Pan American Health Organization, Brazilian Ministry of Health). The proposed clinical rule offers a rapid, low-cost, easy-to-apply strategy to differentiate chikungunya fever from other arbovirus infections during epidemics.

Low Transmission of Chikungunya Virus by Aedes aegypti from Vientiane Capital, Lao PDR

In 2012−2013, chikungunya virus (CHIKV) was the cause of a major outbreak in the southern part of Lao People’s Democratic Republic (Lao PDR). Since then, only a few imported cases, with isolates belonging to different lineages, were recorded between 2014 and 2020 in Vientiane capital and few autochthonous cases of ECSA-IOL lineage were detected in the south of the country in 2020. The CHIKV epidemiological profile contrasts with the continuous and intensive circulation of dengue virus in the country, especially in Vientiane capital. The study’s aim was to investigate the ability of the local field-derived Aedes aegypti population from Vientiane capital to transmit the Asian and ECSA-IOL lineages of CHIKV. Our results revealed that, for both CHIKV lineages, infection rates were low and dissemination rates were high. The transmission rates and efficiencies evidenced a low vector competence for the CHIKV tested. Although this population of Ae. aegypti showed a relatively modest vector competence for these two CHIKV lineages, several other factors could influence arbovirus emergence such as the longevity and density of female mosquitoes. Due to the active circulation of CHIKV in Southeast Asia, investigations on these factors should be done to prevent the risk of CHIKV emergence and spread in Lao PDR and neighboring countries.

Arbovirus Antibody Seroprevalence in the Human Population from Cauca, Colombia

Several arboviruses have emerged or reemerged into the New World during the past several decades, causing outbreaks of significant proportion. In particular, the outbreaks of Dengue virus (DENV), Zika virus, and Chikungunya virus (CHIKV) have been explosive and unpredictable, and have led to significant adverse health effects. These viruses are considered the leading cause of acute undifferentiated febrile illnesses in Colombia. However, Venezuelan equine encephalitis virus (VEEV) is endemic in Colombia, and arboviruses such as the Mayaro virus (MAYV) and the Oropouche virus (OROV) cause febrile illnesses in neighboring countries. Yet, evidence of human exposure to MAYV and OROV in Colombia is scarce. In this study, we conducted a serosurvey study in healthy individuals from the Cauca Department in Colombia. We assessed the seroprevalence of antibodies against multiple arboviruses, including DENV serotype 2, CHIKV, VEEV, MAYV, and OROV. Based on serological analyses, we found that the overall seroprevalence for DENV serotype 2 was 30%, 1% for MAYV, 2.6% for CHIKV, 4.4% for VEEV, and 2% for OROV. This study provides evidence about the circulation of MAYV and OROV in Colombia, and suggests that they-along with VEEV and CHIKV-might be responsible for cases of acute undifferentiated febrile illnesses that remain undiagnosed in the region. The study results also highlight the need to strengthen surveillance programs to identify outbreaks caused by these and other vector-borne pathogens.

Immune response to arbovirus infection in obesity

Obesity is a global health problem that affects 650 million people worldwide and leads to diverse changes in host immunity. Individuals with obesity experience an increase in the size and the number of adipocytes, which function as an endocrine organ and release various adipocytokines such as leptin and adiponectin that exert wide ranging effects on other cells. In individuals with obesity, macrophages account for up to 40% of adipose tissue (AT) cells, three times more than in adipose tissue (10%) of healthy weight individuals and secrete several cytokines and chemokines such as interleukin (IL)-1β, chemokine C-C ligand (CCL)-2, IL-6, CCL5, and tumor necrosis factor (TNF)-α, leading to the development of inflammation. Overall, obesity-derived cytokines strongly affect immune responses and make patients with obesity more prone to severe symptoms than patients with a healthy weight. Several epidemiological studies reported a strong association between obesity and severe arthropod-borne virus (arbovirus) infections such as dengue virus (DENV), chikungunya virus (CHIKV), West Nile virus (WNV), and Sindbis virus (SINV). Recently, experimental investigations found that DENV, WNV, CHIKV and Mayaro virus (MAYV) infections cause worsened disease outcomes in infected diet induced obese (DIO) mice groups compared to infected healthy-weight animals. The mechanisms leading to higher susceptibility to severe infections in individuals with obesity remain unknown, though a better understanding of the causes will help scientists and clinicians develop host directed therapies to treat severe disease. In this review article, we summarize the effects of obesity on the host immune response in the context of arboviral infections. We have outlined that obesity makes the host more susceptible to infectious agents, likely by disrupting the functions of innate and adaptive immune cells. We have also discussed the immune response of DIO mouse models against some important arboviruses such as CHIKV, MAYV, DENV, and WNV. We can speculate that obesity-induced disruption of innate and adaptive immune cell function in arboviral infections ultimately affects the course of arboviral disease. Therefore, further studies are needed to explore the cellular and molecular aspects of immunity that are compromised in obesity during arboviral infections or vaccination, which will be helpful in developing specific therapeutic/prophylactic interventions to prevent immunopathology and disease progression in individuals with obesity.

Honokiol and Alpha-Mangostin Inhibit Mayaro Virus Replication through Different Mechanisms

Mayaro virus (MAYV) is an emerging arbovirus with an increasing circulation across the Americas. In the present study, we evaluated the potential antiviral activity of the following natural compounds against MAYV and other arboviruses: Sanguinarine, (R)-Shikonin, Fisetin, Honokiol, Tanshinone IIA, and α-Mangostin. Sanguinarine and Shikonin showed significant cytotoxicity, whereas Fisetin, Honokiol, Tanshinone IIA, and α-Mangostin were well tolerated in all the cell lines tested. Honokiol and α-Mangostin treatment protected Vero-E6 cells against MAYV-induced damage and resulted in a dose-dependent reduction in viral progeny yields for each of the MAYV strains and human cell lines assessed. These compounds also reduced MAYV viral RNA replication in HeLa cells. In addition, Honokiol and α-Mangostin disrupted MAYV infection at different stages of the virus life cycle. Moreover, Honokiol and α-Mangostin decreased Una, Chikungunya, and Zika viral titers and downmodulated the expression of E1 and nsP1 viral proteins from MAYV, Una, and Chikungunya. Finally, in Honokiol- and α-Mangostin-treated HeLa cells, we observed an upregulation in the expression of type I interferon and specific interferon-stimulated genes, including IFNα, IFNβ, MxA, ISG15, OAS2, MDA-5, TNFα, and IL-1β, which may promote an antiviral cellular state. Our results indicate that Honokiol and α-Mangostin present potential broad-spectrum activity against different arboviruses through different mechanisms.

Genomic Epidemiology Reveals the Circulation of the Chikungunya Virus East/Central/South African Lineage in Tocantins State, North Brazil

The chikungunya virus (CHIKV) is a mosquito-borne virus of the family Togaviridae transmitted to humans by Aedes spp. mosquitoes. In Brazil, imported cases have been reported since June 2014 through two independent introductions, one caused by Asian Lineage in Oiapoque, Amapá state, North Region, and another caused by East/Central/South African (ECSA) in Feira de Santana, Bahia state, Northeast Region. Moreover, there is still limited information about the genomic epidemiology of the CHIKV from surveillance studies. The Tocantins state, located in Northern Brazil, reported an increase in the number of CHIKV cases at the end of 2021 and the beginning of 2022. Thus, to better understand the dispersion dynamics of this viral pathogen in the state, we generated 27 near-complete CHIKV genome sequences from four cities, obtained from clinical samples. Our results showed that the newly CHIKV genomes from Tocantins belonged to the ECSA lineage. Phylogenetic reconstruction revealed that Tocantins' strains formed a single well-supported clade, which appear to be closely related to isolates from the Rio Grande do Norte state (Northeast Brazil) and the Rio de Janeiro state (Southeast Brazil), that experienced an explosive ECSA epidemic between 2016-2019. Mutation analyses showed eleven frequent non-synonymous mutations in the structural and non-structural proteins, indicating the autochthonous transmission of the CHIKV in the state. None of the genomes recovered within the Tocantins samples carry the A226V mutation in the E1 protein associated with increased transmission in A. albopictus. The study presented here highlights the importance of continued genomic surveillance to provide information not only on recording mutations along the viral genome but as a molecular surveillance tool to trace virus spread within the country, to predict events of likely occurrence of new infections, and, as such, contribute to an improved public health service.

Updating the Insecticide Resistance Status of Aedes aegypti and Aedes albopictus in Asia: A Systematic Review and Meta-Analysis

Background: Aedes aegypti and Aedes albopictus are two important vectors of several important arboviruses, including the dengue, chikungunya, and Zika viruses. Insecticide application is an important approach to reduce vector abundance during Aedes spp.-borne outbreaks in the absence of effective vaccines and treatments. However, insecticide overuse can result in the development of resistance, and careful monitoring of resistance markers is required. Methods: This meta-analysis and systematic review explored the spatial and temporal patterns of insecticide resistance in Asia from 2000 to 2021. PubMed, Scopus, EbscoHost, and Embase were used to enhance the search capability. The random-effects model was applied for the 94 studies that met our inclusion criteria for qualitative synthesis and meta-analysis. Results: Four major insecticides were studied (malathion, dichlorodiphenyltrichloroethane, permethrin, and deltamethrin). Dichlorodiphenyltrichloroethane resistance rates were high in both Ae. aegypti and Ae. albopictus (68% and 64%, respectively). Conversely, malathion resistance was less prevalent in Ae. aegypti (3%), and deltamethrin resistance was less common in Ae. albopictus (2%). Ae. aegypti displayed consistently high resistance rates (35%) throughout the study period, whereas the rate of insecticide resistance in Ae. albopictus increased from 5% to 12%. The rates of the major kdr mutations F1534C, V1016G, and S989P were 29%, 26%, and 22%, respectively. Conclusions: Insecticide resistance in both Ae. aegypti and Ae. albopictus is widespread in Asia, although the rates vary by country. Continuous monitoring of the resistance markers and modification of the control strategies will be important for preventing unexpected outbreaks. This systematic review and meta-analysis provided up-to-date information on insecticide resistance in dengue-endemic countries in Asia.

Interactions between seasonal temperature variation and temporal synchrony drive increased arbovirus co-infection incidence

Though instances of arthropod-borne (arbo)virus co-infection have been documented clinically, the overall incidence of arbovirus co-infection and its drivers are not well understood. Now that dengue, Zika and chikungunya viruses are all in circulation across tropical and subtropical regions of the Americas, it is important to understand the environmental and biological conditions that make co-infections more likely to occur. To understand this, we developed a mathematical model of co-circulation of two arboviruses, with transmission parameters approximating dengue, Zika and/or chikungunya viruses, and co-infection possible in both humans and mosquitoes. We examined the influence of seasonal timing of arbovirus co-circulation on the extent of co-infection. By undertaking a sensitivity analysis of this model, we examined how biological factors interact with seasonality to determine arbovirus co-infection transmission and prevalence. We found that temporal synchrony of the co-infecting viruses and average temperature were the most influential drivers of co-infection incidence. Our model highlights the synergistic effect of co-transmission from mosquitoes, which leads to more than double the number of co-infections than would be expected in a scenario without co-transmission. Our results suggest that appreciable numbers of co-infections are unlikely to occur except in tropical climates when the viruses co-occur in time and space.

In Depth Viral Diversity Analysis in Atypical Neurological and Neonatal Chikungunya Infections in Rio de Janeiro, Brazil

Chikungunya virus (CHIKV) is an arthropod-borne virus (arbovirus) transmitted by Aedes mosquitoes. The human infection usually manifests as a febrile and incapacitating arthritogenic illness, self-limiting and non-lethal. However, since 2013, CHIKV spreading through the tropics and to the Americas was accompanied by an increasing number of cases of atypical disease presentation, namely severe neuropathies and neonatal infection due to intrapartum vertical transmission. The pathophysiological mechanisms underlying these conditions have not been fully elucidated. However, arbovirus intrahost genetic diversity is thought to be linked to viral pathogenesis. To determine whether particular viral variants could be somehow associated, we analyzed the intrahost genetic diversity of CHIKV in three infected patients with neurological manifestations and three mothers infected during the intrapartum period, as well as their babies following vertical transmission. No statistically supported differences were observed for the genetic variability (nucleotide substitutions/gene length) along the genome between the groups. However, the newborn and cerebrospinal fluid samples (corresponding to virus passed through the placenta and/or the blood–brain barrier (BBB)) presented a different composition of their intrahost mutant ensembles compared to maternal or patient serum samples, even when concurrent. This finding could be consistent with the unidirectional virus transmission through these barriers, and the effect of selective bottlenecks during the transmission event. In addition, a higher proportion of defective variants (insertions/deletions and stop codons) was detected in the CSF and maternal samples and those were mainly distributed within the viral non-structural genes. Since defective viral genomes in RNA viruses are known to contribute to the outcome of acute viral infections and influence disease severity, their role in these atypical cases should be further investigated. Finally, with the in silico approach adopted, we detected no relevant non-conservative mutational pattern that could provide any hint of the pathophysiological mechanisms underlying these atypical cases. The present analysis represents a unique contribution to our understanding of the transmission events in these cases and generates hypotheses regarding underlying mechanisms, that can be explored further.

Spatio-temporal clusters and patterns of spread of dengue, chikungunya, and Zika in Colombia

Background

Colombia has one of the highest burdens of arboviruses in South America. The country was in a state of hyperendemicity between 2014 and 2016, with co-circulation of several Aedes-borne viruses, including a syndemic of dengue, chikungunya, and Zika in 2015.

Methodology/Principal findings

We analyzed the cases of dengue, chikungunya, and Zika notified in Colombia from January 2014 to December 2018 by municipality and week. The trajectory and velocity of spread was studied using trend surface analysis, and spatio-temporal high-risk clusters for each disease in separate and for the three diseases simultaneously (multivariate) were identified using Kulldorff’s scan statistics. During the study period, there were 366,628, 77,345 and 74,793 cases of dengue, chikungunya, and Zika, respectively, in Colombia. The spread patterns for chikungunya and Zika were similar, although Zika’s spread was accelerated. Both chikungunya and Zika mainly spread from the regions on the Atlantic coast and the south-west to the rest of the country. We identified 21, 16, and 13 spatio-temporal clusters of dengue, chikungunya and Zika, respectively, and, from the multivariate analysis, 20 spatio-temporal clusters, among which 7 were simultaneous for the three diseases. For all disease-specific analyses and the multivariate analysis, the most-likely cluster was identified in the south-western region of Colombia, including the Valle del Cauca department.

Conclusions/Significance

The results further our understanding of emerging Aedes-borne diseases in Colombia by providing useful evidence on their potential site of entry and spread trajectory within the country, and identifying spatio-temporal disease-specific and multivariate high-risk clusters of dengue, chikungunya, and Zika, information that can be used to target interventions.

Dengue, chikungunya, and Zika are diseases transmitted to humans by the bite of infected Aedes mosquitoes. Between 2014 and 2016 chikungunya and Zika viruses started causing outbreaks in Colombia, one of the countries historically most affected by dengue. We used case counts of the diseases by municipality and week to study the spread trajectory of chikungunya and Zika within Colombia’s territory, and to identify space-time high-risk clusters, i.e., the areas and time periods that dengue, chikungunya, and Zika were more present. Chikungunya and Zika spread similarly in Colombia, but Zika spread faster. The Atlantic coast, a famous touristic destination in the country, was likely the place of entry of chikungunya and Zika in Colombia. The south-western region was identified as a high-risk cluster for all three diseases in separate and simultaneously. This region has a favorable climate for the Aedes mosquitoes and other characteristics that facilitate the diseases’ transmission, such as social deprivation and high population mobility. Our results provide useful information on the locations that should be prioritized for interventions to prevent the entry of new diseases transmitted by Aedes and to reduce the burden of dengue, chikungunya and Zika where they are established.

Climate Change and Cascading Risks from Infectious Disease

Climate change is adversely affecting the burden of infectious disease throughout the world, which is a health security threat. Climate-sensitive infectious disease includes vector-borne diseases such as malaria, whose transmission potential is expected to increase because of enhanced climatic suitability for the mosquito vector in Asia, sub-Saharan Africa, and South America. Climatic suitability for the mosquitoes that can carry dengue, Zika, and chikungunya is also likely to increase, facilitating further increases in the geographic range and longer transmission seasons, and raising concern for expansion of these diseases into temperate zones, particularly under higher greenhouse gas emission scenarios. Early spring temperatures in 2018 seem to have contributed to the early onset and extensive West Nile virus outbreak in Europe, a pathogen expected to expand further beyond its current distribution, due to a warming climate. As for tick-borne diseases, climate change is projected to continue to contribute to the spread of Lyme disease and tick-borne encephalitis, particularly in North America and Europe. Schistosomiasis is a water-borne disease and public health concern in Africa, Latin America, the Middle East, and Southeast Asia; climate change is anticipated to change its distribution, with both expansions and contractions expected. Other water-borne diseases that cause diarrheal diseases have declined significantly over the last decades owing to socioeconomic development and public health measures but changes in climate can reverse some of these positive developments. Weather and climate events, population movement, land use changes, urbanization, global trade, and other drivers can catalyze a succession of secondary events that can lead to a range of health impacts, including infectious disease outbreaks. These cascading risk pathways of causally connected events can result in large-scale outbreaks and affect society at large. We review climatic and other cascading drivers of infectious disease with projections under different climate change scenarios. Supplementary file1 (MP4 328467 KB).

The Seroprevalence and Hidden Burden of Chikungunya Endemicity and Malaria Mono- and Coinfection in Nigeria

Background: Mosquito-borne infections are of global health concern because of their rapid spread and upsurge, which creates a risk for coinfections. Chikungunya, an arbovirus disease transmitted by Aedes aegypti or A. albopictus, and malaria, a parasitic disease transmitted by Anopheles gambiae, are prevalent in Nigeria and neighbouring countries, but their burden and possible coinfections are poorly understood. In this study, we investigated the seroprevalence, hidden burden and endemicity of chikungunya and malaria in three regions in Nigeria. Methods: A cross-sectional sero-survey was conducted on 871 participants in three regions of Nigeria. The samples were collected from outpatients employing simple random sampling. All serum sample analyses were performed using CHIKV virus-like particle recomLine Tropical Fever for the presence of arboviral antibody serological marker IgG immunoblot for chikungunya and malaria RDT (Rapid Diagnostic Test) for malaria parasites. Results: The seroprevalences of chikungunya and malaria mono-infection were 64.9% and 27.7%, respectively, while the coinfection seroprevalence was 71.9%. The central (69.5%) and northern (67.0%) regions showed more significant seroprevalences than the southern region (48.0%). The seroprevalence and the hidden burden of chikungunya and malaria infections varied across the three geographical regions. Conclusions: This study highlighted an unexpectedly high seroprevalence and hidden endemicity of chikungunya and a less surprising high malaria endemicity in three regions of Nigeria.

Development of a next-generation chikungunya virus vaccine based on the HydroVax platform

Chikungunya virus (CHIKV) is an emerging/re-emerging mosquito-borne pathogen responsible for explosive epidemics of febrile illness characterized by debilitating polyarthralgia and the risk of lethal infection among the most severe cases. Despite the public health risk posed by CHIKV, no vaccine is currently available. Using a site-directed hydrogen peroxide-based inactivation approach, we developed a new CHIKV vaccine, HydroVax-CHIKV. This vaccine technology was compared to other common virus inactivation approaches including β-propiolactone (BPL), formaldehyde, heat, and ultraviolet (UV) irradiation. Heat, UV, and BPL were efficient at inactivating CHIKV-181/25 but caused substantial damage to neutralizing epitopes and failed to induce high-titer neutralizing antibodies in vaccinated mice. HydroVax-CHIKV and formaldehyde-inactivated CHIKV retained intact neutralizing epitopes similar to live virus controls but the HydroVax-CHIKV approach demonstrated a more rapid rate of virus inactivation. HydroVax-CHIKV vaccination induced high neutralizing responses to homologous and heterologous CHIKV clades as well as to other alphaviruses including Mayaro virus, O’nyong’nyong virus, and Una virus. Following heterologous infection with CHIKV-SL15649, HydroVax-CHIKV-immunized mice were protected against viremia, CHIKV-associated arthritic disease, and lethal CHIKV infection by an antibody-dependent mechanism. In contrast, animals vaccinated with Heat- or UV-inactivated virus showed no protection against viremia in addition to demonstrating significantly exacerbated CD4⁺ T cell-mediated footpad swelling after CHIKV infection. Together, these results demonstrate the risks associated with using suboptimal inactivation methods that fail to elicit protective neutralizing antibody responses and show that HydroVax-CHIKV represents a promising new vaccine candidate for prevention of CHIKV-associated disease.

Chikungunya virus (CHIKV) is a mosquito-borne virus that has gained significant attention due to its ability to cause large epidemics and to spread beyond endemic countries through international travelers. Despite substantial efforts over the course of many years, a licensed CHIKV vaccine remains unavailable for protecting at-risk populations. Our research group has established an advanced site-directed oxidation system, termed HydroVax, for the development of new vaccines. Here, we describe a novel CHIKV vaccine that utilizes this peroxide-based vaccine platform and demonstrates greatly improved antiviral immunity compared to other traditional virus inactivation approaches as well as complete protection against viremia, CHIKV-associated arthritic disease and lethal CHIKV infection in robust preclinical mouse models. The HydroVax-CHIKV vaccine not only induced neutralizing antibodies to geographically diverse strains of CHIKV, but also elicited neutralizing antibody responses to other clinically important alphaviruses including, Mayaro, O’nyong’nyong, and Una virus. Together, this indicates that this vaccine not only protects against CHIKV infection but may potentially provide immunity across a broader range of virulent alphaviruses as well.

Chikungunya Virus Asian Lineage Infection in the Amazon Region Is Maintained by Asiatic and Caribbean-Introduced Variants

The simultaneous transmission of two lineages of the chikungunya virus (CHIKV) was discovered after the pathogen’s initial arrival in Brazil. In Oiapoque (Amapá state, north Brazil), the Asian lineage (CHIKV-Asian) was discovered, while in Bahia state, the East-Central-South-African lineage (CHIKV-ECSA) was discovered (northeast Brazil). Since then, the CHIKV-Asian lineage has been restricted to the Amazon region (mostly in the state of Amapá), whereas the ECSA lineage has expanded across the country. Despite the fact that the Asian lineage was already present in the Amazon region, the ECSA lineage brought from the northeast caused a large outbreak in the Amazonian state of Roraima (north Brazil) in 2017. Here, CHIKV spread in the Amazon region was studied by a Zika–Dengue–Chikungunya PCR assay in 824 serum samples collected between 2013 and 2016 from individuals with symptoms of viral infection in the Amapá state. We found 11 samples positive for CHIKV-Asian, and, from these samples, we were able to retrieve 10 full-length viral genomes. A comprehensive phylogenetic study revealed that nine CHIKV sequences came from a local transmission cluster related to Caribbean strains, whereas one sequence was related to sequences from the Philippines. These findings imply that CHIKV spread in different ways in Roraima and Amapá, despite the fact that both states had similar climatic circumstances and mosquito vector frequencies.

Immunological implications of diverse production approaches for Chikungunya virus-like particle vaccines

Chikungunya virus (CHIKV), an arbovirus from the Alphavirus genus, causes sporadic outbreaks and epidemics and can cause acute febrile illness accompanied by severe long-term arthralgias. Over 20 CHIKV vaccine candidates have been developed over the last two decades, utilizing a wide range of vaccine platforms, including virus-like particles (VLP). A CHIKV VLP vaccine candidate is among three candidates in late-stage clinical testing and has potentially promising data in nonclinical and clinical studies exploring safety and vaccine immunogenicity. Despite the consistency of the CHIKV VLP structure, vaccine candidates vary significantly in protein sequence identity, structural protein expression cassettes and their mode of production. Here, we explore the impact of CHIKV VLP coding sequence variation and the chosen expression platform, which affect VLP expression yields, antigenicity and overall vaccine immunogenicity. Additionally, we explore the potential of the CHIKV VLP platform to be modified to elicit protection against other pathogens.

EVITA Dengue: a cluster-randomized controlled trial to EValuate the efficacy of Wolbachia-InfecTed Aedes aegypti mosquitoes in reducing the incidence of Arboviral infection in Brazil

BACKGROUND

Arboviruses transmitted by Aedes aegypti including dengue, Zika, and chikungunya are a major global health problem, with over 2.5 billion at risk for dengue alone. There are no licensed antivirals for these infections, and safe and effective vaccines are not yet widely available. Thus, prevention of arbovirus transmission by vector modification is a novel approach being pursued by multiple researchers. However, the field needs high-quality evidence derived from randomized, controlled trials upon which to base the implementation and maintenance of vector control programs. Here, we report the EVITA Dengue trial design (DMID 17-0111), which assesses the efficacy in decreasing arbovirus transmission of an innovative approach developed by the World Mosquito Program for vector modification of Aedes mosquitoes by Wolbachia pipientis.

METHODS

DMID 17-0111 is a cluster-randomized trial in Belo Horizonte, Brazil, with clusters defined by primary school catchment areas. Clusters (n = 58) will be randomized 1:1 to intervention (release of Wolbachia-infected Aedes aegypti mosquitoes) vs. control (no release). Standard vector control activities (i.e., insecticides and education campaigns for reduction of mosquito breeding sites) will continue as per current practice in the municipality. Participants (n = 3480, 60 per cluster) are children aged 6-11 years enrolled in the cluster-defining school and living within the cluster boundaries who will undergo annual serologic surveillance for arboviral infection. The primary objective is to compare sero-incidence of arboviral infection between arms.

DISCUSSION

DMID 17-0111 aims to determine the efficacy of Wolbachia-infected mosquito releases in reducing human infections by arboviruses transmitted by Aedes aegypti and will complement the mounting evidence for this method from large-scale field releases and ongoing trials. The trial also represents a critical step towards robustness and rigor for how vector control methods are assessed, including the simultaneous measurement and correlation of entomologic and epidemiologic outcomes. Data from this trial will inform further the development of novel vector control methods.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04514107 . Registered on 17 August 2020 Primary sponsor: National Institute of Health, National Institute of Allergy and Infectious Diseases.

Distinct Cellular Tropism and Immune Responses to Alphavirus Infection

Alphaviruses are emerging and reemerging viruses that cause disease syndromes ranging from incapacitating arthritis to potentially fatal encephalitis. While infection by arthritogenic and encephalitic alphaviruses results in distinct clinical manifestations, both virus groups induce robust innate and adaptive immune responses. However, differences in cellular tropism, type I interferon induction, immune cell recruitment, and B and T cell responses result in differential disease progression and outcome. In this review, we discuss aspects of immune responses that contribute to protective or pathogenic outcomes after alphavirus infection. Expected final online publication date for the Annual Review of Immunology, Volume 40 is April 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Dynamics of a Fractional-Order Chikungunya Model with Asymptomatic Infectious Class

In this paper, a nonlinear fractional-order chikungunya disease model that incorporates asymptomatic infectious individuals is proposed and analyzed. The main interest of this work is to investigate the role of memory effects on the dynamics of chikungunya. Qualitative analysis of the model's equilibria showed that there exists a threshold quantity which governs persistence and extinction of the disease. Model parameters were estimated based on the 2015 weekly reported cases in Colombia. The Adams-Bashforth-Moulton method was used to numerically solve the proposed model. We investigated the role of asymptomatic infectious patients on short- and long-term dynamics of the diseases. We also determined threshold levels for the efficacy of preventative strategies that results in effective management of the disease. We believe that our model can provide invaluable insights for public health authorities to predict the effect of chikungunya transmission and analyze its underlying factors and to guide new control efforts.

Serological Responses in Patients Infected with Mayaro Virus and Evaluation of Cross-Protective Responses against Chikungunya Virus

Mayaro virus (MAYV) is an alphavirus endemic to both Latin America and the Caribbean. Recent reports have questioned the ability of MAYV and its close relative, Chikungunya virus (CHIKV), to generate cross-reactive, neutralizing antibodies to one another. Since CHIKV was introduced to South America in 2013, discerning whether individuals have cross-reactive antibodies or whether they have had exposures to both viruses previously has been difficult. Using samples obtained from people infected with MAYV prior to the introduction of CHIKV in the Americas, we performed neutralizing assays and observed no discernable neutralization of CHIKV by sera from patients previously infected with MAYV. These data suggest that a positive CHIKV neutralization test cannot be attributed to prior exposure to MAYV and that previous exposure to MAYV may not be protective against a subsequent CHIKV infection.

Current Understanding of the Role of T Cells in Chikungunya, Dengue and Zika Infections

Arboviral infections such as Chikungunya (CHIKV), Dengue (DENV) and Zika (ZIKV) are a major disease burden in tropical and sub-tropical countries, and there are no effective vaccinations or therapeutic drugs available at this time. Understanding the role of the T cell response is very important when designing effective vaccines. Currently, comprehensive identification of T cell epitopes during a DENV infection shows that CD8 and CD4 T cells and their specific phenotypes play protective and pathogenic roles. The protective role of CD8 T cells in DENV is carried out through the killing of infected cells and the production of proinflammatory cytokines, as CD4 T cells enhance B cell and CD8 T cell activities. A limited number of studies attempted to identify the involvement of T cells in CHIKV and ZIKV infection. The identification of human immunodominant ZIKV viral epitopes responsive to specific T cells is scarce, and none have been identified for CHIKV. In CHIKV infection, CD8 T cells are activated during the acute phase in the lymph nodes/blood, and CD4 T cells are activated during the chronic phase in the joints/muscles. Studies on the role of T cells in ZIKV-neuropathogenesis are limited and need to be explored. Many studies have shown the modulating actions of T cells due to cross-reactivity between DENV-ZIKV co-infections and have repeated heterologous/homologous DENV infection, which is an important factor to consider when developing an effective vaccine.

Prevention and control of dengue and Chikungunya in Colombia: A cost-effectiveness analysis

Background

Chikungunya and dengue are emerging diseases that have caused large outbreaks in various regions of the world. Both are both spread by Aedes aegypti and Aedes albopictus mosquitos. We developed a dynamic transmission model of chikungunya and dengue, calibrated to data from Colombia (June 2014 –December 2017).

Methodology/Principal findings

We evaluated the health benefits and cost-effectiveness of residual insecticide treatment, long-lasting insecticide-treated nets, routine dengue vaccination for children aged 9, catchup vaccination for individuals aged 10–19 or 10–29, and portfolios of these interventions. Model calibration resulted in 300 realistic transmission parameters sets that produced close matches to disease-specific incidence and deaths. Insecticide was the preferred intervention and was cost-effective. Insecticide averted an estimated 95 chikungunya cases and 114 dengue cases per 100,000 people, 61 deaths, and 4,523 disability-adjusted life years (DALYs). In sensitivity analysis, strategies that included dengue vaccination were cost-effective only when the vaccine cost was 14% of the current price.

Conclusions/Significance

Insecticide to prevent chikungunya and dengue in Colombia could generate significant health benefits and be cost-effective. Because of limits on diagnostic accuracy and vaccine efficacy, the cost of dengue testing and vaccination must decrease dramatically for such vaccination to be cost-effective in Colombia. The vectors for chikungunya and dengue have recently spread to new regions, highlighting the importance of understanding the effectiveness and cost-effectiveness of policies aimed at preventing these diseases.

Chikungunya and dengue are emerging diseases that have caused large outbreaks in various regions of the world. Both are both spread by Aedes aegypti and Aedes albopictus mosquitos. To evaluate the effectiveness and cost-effectiveness of interventions aimed at controlling either of these diseases, it is important to consider the potential effects on both diseases, as an intervention that reduces the mosquito population will reduce the spread of both diseases. We developed a dynamic transmission model of chikungunya and dengue, calibrated to data from Colombia. We evaluated the health benefits and cost-effectiveness of the following interventions: residual insecticide treatment, long-lasting insecticide-treated nets, routine dengue vaccination for children aged 9, catchup dengue vaccination for individuals aged 10–19 or 10–29, and portfolios of these interventions. In all vaccination scenarios, we considered testing for previous exposure to dengue. We found that insecticide to prevent chikungunya and dengue in Colombia could generate significant health benefits and be cost-effective. While the dengue vaccine was effective in preventing cases and deaths, costs of diagnostic testing and vaccination must decrease for dengue vaccination to be considered cost-effective.