Mosquito-transmitted Disease Research Articles

Leucinostatins from fungal extracts block malaria transmission to mosquitoes

BackgroundMalaria is a mosquito-transmitted disease that kills more than half a million people annually. The lack of effective malaria vaccines and recently increasing malaria cases urge innovative approaches to prevent malaria. Previously, we reported that the extract from the soil-dwelling fungus Purpureocillium lilacinum, a common fungus from the soil, reduced Plasmodium falciparum oocysts in Anopheles gambiae midguts after mosquitoes contacted the treated surface before feeding.MethodsWe used liquid chromatography to fraction fungal crude extract and tract the active fraction using a contact-wise approach and standard membrane feeding assays. The purified small molecules were analyzed using precise mass spectrometry and tandem mass spectrometry.ResultsWe isolated four active small molecules from P. lilacinum and determined them as leucinostatin A, B, A2, and B2. Pre-exposure of mosquitoes via contact with very low-concentration leucinostatin A significantly reduced the number of oocysts. The half-maximal response or inhibition concentration (EC50) via pre-exposure was 0.7 mg/m2, similar to atovaquone but lower than other known antimalarials. The inhibitory effect of leucinostatin A against P. falciparum during intraerythrocytic development, gametogenesis, sporogonic development, and ookinete formation, with the exception of oocyst development, suggests that leucinostatins play a part during parasite invasion of new cells.ConclusionsLeucinostatins, secondary metabolites from P. lilacinum disrupt malaria development, particular transmission to mosquitoes by contact. The contact-wise malaria control as a nonconventional approach is highly needed in malaria-endemic areas.Graphical

From bench to clinic: the development of VLA1553/IXCHIQ, a live-attenuated chikungunya vaccine.

Over the past 20 years, over 5 million cases of chikungunya, a mosquito-transmitted viral disease, have been reported in over 110 countries. Until recently, preventative strategies for chikungunya were largely ineffective, relying on vector control and individual avoidance of mosquito bites. This review outlines the preclinical and clinical efficacy and safety data that led to the approval of VLA1553 (IXCHIQ®), a live-attenuated vaccine against chikungunya disease. It also describes the innovative development pathway of VLA1553, based on an immunological surrogate of protection, and discusses ongoing and future post-licensure studies. In mice and non-human primate models, VLA1553 elicited high titres of neutralizing antibodies, conferred protection against wild-type chikungunya virus challenge and raised no safety concerns. A Phase 1 clinical trial of VLA1553 demonstrated 100% seroconversion among 120 healthy participants, with sustained neutralizing antibody titres after 12 months. These results and determination of a surrogate marker of protection led to advancement of VLA1553 directly into Phase 3 clinical development, as agreed with the US Food and Drug Administration (FDA) and the European Medicines Agency. The pivotal Phase 3 trial met its primary immunogenicity endpoint, achieving seroprotective levels based on immuno-bridging in baseline seronegative participants 28 days post-vaccination. These findings enabled submission of a Biologics License Application to the FDA for accelerated approval of VLA1553 in the US for adults aged ≥18 years. Ongoing and planned studies will confirm the clinical efficacy/effectiveness and safety of VLA1553 in adults and younger individuals, and will generate data in chikungunya endemic countries that have the highest unmet need. VLA1553 is the first vaccine approved for the prevention of chikungunya disease in adults, following accelerated development based on a serological surrogate marker of protection. VLA1553 adds to strategies to reduce the spread and burden of chikungunya in endemic populations and travellers.

Preliminary analysis of socioeconomic variable correlation with geospatial modeling in Costa Rica dengue epidemics

Dengue is a mosquito-transmitted disease that affects more than 5 million people worldwide. It is endemic in more than 100 countries and it has presence in 5 continents. Understanding the dynamics of dengue epidemics is crucial in reducing the massive public health impact this disease has. However, dengue is a complex phenomenon. There are many variables that contribute to the spread of the virus and the interconnection of those variables is not clear. We set out to explore the correlation of socioeconomic variables in dengue epidemics by using a geospatial model. Our study is centered in Costa Rica, a country with a repeated affectation by the virus. We found a possible relationship between number of dengue cases and some socioeconomic variables (dwellings with water pipes, location of work), which open the gates to consider including them in a more sophisticated epidemiological model.

Results of Integrated Transmission Assessment Surveys for Lymphatic Filariasis and Malaria in Haiti, 2017-2022.

Haiti is endemic for lymphatic filariasis (LF) and malaria, two mosquito-transmitted parasitic diseases targeted for elimination. The World Health Organization recommends a transmission assessment survey (TAS-1) to determine if LF prevalence is significantly beneath putative transmission thresholds (<2% antigen prevalence in Haiti, where Culex is the primary vector for Wuchereria bancrofti) to stop mass drug administration (MDA). Repeated TASs (TAS-2 and TAS-3) are recommended at 2-3-year intervals during post-treatment surveillance. From 2017 to 2022, The Carter Center assisted the Haitian Ministry of Public Health and Population in conducting 15 TASs in 11 evaluation units (EUs) encompassing 54 of the country's 146 districts. Children 6-7 years old were assessed for circulating filarial antigen (CFA) by Filariasis Test Strip: n = 5,239 in TAS-1; n = 11,866 in TAS-2; and n = 1,842 in TAS-3, of whom eight (0.15%), 20 (0.17%), and eight (0.43%) tested positive, respectively. The number of positive results in children was less than the threshold in each EU. When available, participants (n = 16,663) were also tested for malaria by rapid diagnostic test, with 31 (0.19%) children testing positive for Plasmodium falciparum. Integrated TASs provided an efficient means to collect epidemiological data for LF and malaria in Haiti. Results indicated thresholds for stopping and maintaining the halt of MDA for LF have been achieved in all EUs, with the halt of MDA for 571,358 people in four districts and the first TAS-3 surveys conducted in Haiti. Investigations are needed to assess the potential of ongoing LF transmission, especially in areas where CFA-positive samples were detected in TAS-3.

Exploring fine-scale urban landscapes using satellite data to predict the distribution of Aedes mosquito breeding sites

BackgroundThe spread of mosquito-transmitted diseases such as dengue is a major public health issue worldwide. The Aedes aegypti mosquito, a primary vector for dengue, thrives in urban environments and breeds mainly in artificial or natural water containers. While the relationship between urban landscapes and potential breeding sites remains poorly understood, such a knowledge could help mitigate the risks associated with these diseases. This study aimed to analyze the relationships between urban landscape characteristics and potential breeding site abundance and type in cities of French Guiana (South America), and to evaluate the potential of such variables to be used in predictive models.MethodsWe use Multifactorial Analysis to explore the relationship between urban landscape characteristics derived from very high resolution satellite imagery, and potential breeding sites recorded from in-situ surveys. We then applied Random Forest models with different sets of urban variables to predict the number of potential breeding sites where entomological data are not available.ResultsLandscape analyses applied to satellite images showed that urban types can be clearly identified using texture indices. The Multiple Factor Analysis helped identify variables related to the distribution of potential breeding sites, such as buildings class area, landscape shape index, building number, and the first component of texture indices. Models predicting the number of potential breeding sites using the entire dataset provided an R² of 0.90, possibly influenced by overfitting, but allowing the prediction over all the study sites. Predictions of potential breeding sites varied highly depending on their type, with better results on breeding sites types commonly found in urban landscapes, such as containers of less than 200 L, large volumes and barrels. The study also outlined the limitation offered by the entomological data, whose sampling was not specifically designed for this study. Model outputs could be used as input to a mosquito dynamics model when no accurate field data are available.ConclusionThis study offers a first use of routinely collected data on potential breeding sites in a research study. It highlights the potential benefits of including satellite-based characterizations of the urban environment to improve vector control strategies.

Effects of sexual and vertical transmission on Zika virus dynamics under environmental fluctuations

Zika is a mosquito-transmitted viral disease which may spread directly by the vector or sexual transmission. Zika virus may persist in semen and urine for a long time after disappearance from the blood, those persons are known as the convalescent humans. It can also be transmitted vertically among mosquitoes. In this paper, we have considered an eight-compartment Zika model to study the effect of all the said aspects on the virus dynamics in deterministic as well as stochastic environment. In analytic part, we have computed basic reproduction number and discussed stability of different equilibria. We have shown the proposed model undergoes through transcritical bifurcation when the reproduction number is unity and validate the model with real infection data of Dominican Republic in 2016. To study the model in stochastic environments, the additive noise is taken into consideration which is formulated considering the standard Brownian white noises proportional to each class. We have obtained the condition for disease extinction and persistence in mean. All theoretical findings are justified by numerical simulations. Lastly, the paper is ended with some conclusions.

Community and health worker perspectives on malaria in Meghalaya, India: covering the last mile of elimination by 2030

BackgroundMalaria remains a public health problem in regions of Northeastern India because of favourable bio-geographic transmission conditions, poor access to routine healthcare, and inadequate infrastructure for public health and disease prevention. This study was undertaken to better understand community members’ and health workers’ perceptions of malaria, as well as their knowledge, attitudes, and prevention practices related to the disease in Meghalaya state.MethodsThe study included participants from three malaria endemic districts: West Khasi Hills, West Jaiñtia Hills, and South Garo Hills from 2019 to 2021. A total of 82 focus group discussions (FGD) involving 694 community members and 63 in-depth interviews (IDI) with health personnel and traditional healers residing within the three districts were conducted. A thematic content analysis approach was employed, using NVivo12 software for data management.ResultsMost participants reported a perceived reduction in malaria during recent years, attributing this to changes in attitudes and behaviours in health seeking, and to more effective government interventions. Local availability of testing and treatment, and an improved, more responsive health system contributed to changing attitudes. Long-lasting insecticidal nets (LLINs) were largely preferred over indoor residual spraying (IRS), as LLINs were perceived to be effective and more durable. Community members also reported using personal protective measures such as applying repellents, burning neem tree leaves, straw/egg trays, wearing long sleeve clothes, and applying ointments or oils to protect themselves from mosquito bites. While most participants acknowledged the role of mosquitoes in malaria transmission, other conditions that are not mosquito-borne were also attributed to mosquitoes by some participants. The communities surveyed have largely shifted from seeking treatment for malaria from traditional healers to using public facilities, although some participants reported switching between the two or using both simultaneously. Improved understanding of cerebral malaria, which some participants previously attributed to mental illness due to ‘bad spirits’, is an example of how cultural and ritualistic practices have changed.ConclusionThe findings reveal diverse perceptions among community members regarding malaria, its prevention, practices to prevent mosquito-transmitted diseases, and their opinions about the healthcare system. A key finding was the shift in malaria treatment-seeking preferences of community members from traditional healers to the public sector. This shift highlights the changing dynamics and increasing acceptance of modern healthcare practices for malaria treatment and prevention within tribal and/or indigenous communities. By recognizing these evolving attitudes, policymakers and healthcare providers can better tailor their interventions and communication strategies to more effectively address ongoing needs and concerns as India faces the ‘last mile’ in malaria elimination.

Dengue Vaccine: Challenges and Limitations

Dengue is a common mosquito-transmitted viral infectious disease. Due to global warming and other climate changes, the dengue virus vector Aedes aegypti mosquito is breeding rapidly and spreading the dengue worldwide. As a result, every year, millions of people are infected by the dengue virus and tolls thousands of lives across the world. World Health Organization (WHO) has given a terrible message that dengue can become as an epidemic. Therefore, the invention of an effective dengue vaccine is a way to build the body’s immunity to fight against the disease. Efforts to develop a vaccine against dengue have been ongoing for decades. Currently, Dengvaxia is approved for use by individuals to prevent dengue with some limitations. Another vaccine, Qdenga is also shown to be effective against verities of dengue virus serotypes but this vaccine is not approved by the USA Food and Drug Administration (FDA) yet. Neither Dengvaxia nor Qdenga has approved in Bangladesh and other low and middle-economic countries due to its conservative approach, controversy and lack of WHO guidelines on dengue vaccine. KYAMC Journal Volume: 14, No: 03, October 2023: 172-174.

Establishment and application of an indirect ELISA for Getah virus E2 antibody detection

Getah virus (GETV) is a mosquito-transmitted disease that affects animals, causing fever, aseptic meningitis, and abortion. Its prevalence in China poses risks to both animal health and public well-being. Currently, there is a scarcity of seroepidemiological data on GETV due to the absence of commercial antibody detection kits for pigs. The aim of this study is to develop a rapid, accurate, and sensitive ELISA, providing a reliable tool for GETV seroepidemiology and laying the foundation for future commercial assay development. In this study, we removed specific hydrophobic domains and intracellular structures from E2 proteins and constructed the recombinant plasmid pCold-TF-E2. The recombinant protein was expressed using a prokaryotic expression system, and efficient purification of the rE2 protein was achieved using a nickel affinity column. The purified rE2 protein is suitable for the development of an indirect ELISA (rE2 ELISA). Following the optimization of reaction conditions for the rE2-ELISA, the cut-off value was 0.356. Additionally, the rE2-ELISA method showed a positive rate of 37.1% for IgG antibodies against GETV when testing 986 pig clinical serum samples collected from pigs in Sichuan between May 2022 and September 2022. The rE2-ELISA method displayed a 95.1% overall agreement with VNT, boasting a sensitivity of 98.2% and a specificity of 92.6%. These results indicate that IgG ELISA based on rE2 protein is an efficient and economical method for the detection of GETV antibodies in pigs, facilitating the diagnosis and prevention of GETV.

Quantifying the relationship between arboviral infection prevalence and human mobility patterns among participants of the Communities Organized to Prevent Arboviruses cohort (COPA) in southern Puerto Rico.

Human movement is increasingly being recognized as a major driver of arbovirus risk and dissemination. The Communities Organized to Prevent Arboviruses (COPA) study is a cohort in southern Puerto Rico to measure arboviral prevalence, evaluate interventions, and collect mobility data. To quantify the relationship between arboviral prevalence and human mobility patterns, we fit multilevel logistic regression models to estimate odds ratios for mobility-related predictors of positive chikungunya IgG or Zika IgM test results collected from COPA, assuming mobility data does not change substantially from year to year. From May 8, 2018-June 8, 2019, 39% of the 1,845 active participants during the study period had a positive arboviral seroprevalence result. Most (74%) participants reported spending five or more weekly hours outside of their home. A 1% increase in weekly hours spent outside the home was associated with a 4% (95% confidence interval (CI): 2-7%) decrease in the odds of testing positive for arbovirus. After adjusting for age and whether a person had air conditioning (AC) at home, any time spent in a work location was protective against arbovirus infection (32% decrease, CI: 9-49%). In fact, there was a general decreased prevalence for individuals who visited locations that were inside and had AC or screens, regardless of the type of location (32% decrease, CI: 12-47%). In this population, the protective characteristics of locations visited appear to be the most important driver of the relationship between mobility and arboviral prevalence. This relationship indicates that not all mobility is the same, with elements like screens and AC providing protection in some locations. These findings highlight the general importance of AC and screens, which are known to be protective against mosquitoes and mosquito-transmitted diseases.

Mosquito densovirus significantly reduces the vector susceptibility to dengue virus serotype 2 in Aedes albopictus mosquitoes (Diptera: Culicidae)

BackgroundDengue virus (DENV) is a major public health threat, with Aedes albopictus being the confirmed vector responsible for dengue epidemics in Guangzhou, China. Mosquito densoviruses (MDVs) are pathogenic mosquito-specific viruses, and a novel MDV was previously isolated from Ae. albopictus in Guangzhou. This study aims to determine the prevalence of MDVs in wild Ae. albopictus populations and investigate their potential interactions with DENV and impact on vector susceptibility for DENV.MethodsThe prevalence of MDV in wild mosquitoes in China was investigated using open access sequencing data and PCR detection in Ae. albopictus in Guangzhou. The viral infection rate and titers in MDV-persistent C6/36 cells were evaluated at 12, 24, 48, 72, 96, and 120 h post infection (hpi) by indirect immunofluorescence assay (IFA) and real time quantitative PCR (RT-qPCR). The midgut infection rate (MIR), dissemination rate (DR), and salivary gland infection rate (SGIR) in various tissues of MDV-infected mosquitoes were detected and quantified at 0, 5, 10, and 15 days post infection (dpi) by RT-PCR and RT-qPCR. The chi-square test evaluated dengue virus serotype 2 (DENV-2) and Aedes aegypti densovirus (AaeDV) infection rates and related indices in mosquitoes, while Tukey's LSD and t-tests compared viral titers in C6/36 cells and tissues over time.ResultsThe results revealed a relatively wide distribution of MDVs in Aedes, Culex, and Anopheles mosquitoes in China and an over 68% positive rate. In vitro, significant reductions in DENV-2 titers in supernatant at 120 hpi, and an apparent decrease in DENV-2-positive cells at 96 and 120 hpi were observed. In vivo, DENV-2 in the ovaries and salivary glands was first detected at 10 dpi in both monoinfected and superinfected Ae. albopictus females, while MDV superinfection with DENV-2 suppressed the salivary gland infection rate at 15 dpi. DENV-2 titer in the ovary and salivary glands of Ae. albopictus was reduced in superinfected mosquitoes at 15 dpi.ConclusionsMDVs is widespread in natural mosquito populations, and replication of DENV-2 is suppressed in MDV-infected Ae. albopictus, thus reducing vector susceptibility to DENV-2. Our study supports the hypothesis that MDVs may contribute to reducing transmission of DENV and provides an alternative strategy for mosquito-transmitted disease control.Graphical abstract

Impact of Mosquito Gut Microbiota on Propagating Pathogenic Infections

The mosquito vectors of various human diseases host a diversified microbial community. These microbiomes seem to be beneficial in several aspects of mosquito biology. They can influence mosquitoes’ susceptibility to various pathogenic infections, therefore affecting the vectorial capacity of mosquitoes through different direct or indirect mechanisms. These microbes act as natural barriers against several mosquito-transmitted infectious diseases. They may be considered as a new transmission-blocking strategy to limit the transmission of pathogens like Plasmodium, Trypanosome, Zika, Dengue and Chikungunya viruses, and filarial parasites. It is through an understanding of the interaction between the mosquito, its microbiota, and the transmitted pathogens that some promising approaches may be developed for limiting the transmission of pathogenic diseases.In this review, we investigate the role of mosquito’s gut microbiome in the propagation of pathogenic infections. It is summarized here in a brief manner how the current knowledge is used for the purpose of limiting the transmission of mosquito-borne diseases through the alteration of mosquitoes' vector capacities.

Performance of VIDAS® Diagnostic Tests for the Automated Detection of Dengue Virus NS1 Antigen and of Anti-Dengue Virus IgM and IgG Antibodies: A Multicentre, International Study

Dengue is a serious mosquito-transmitted disease caused by the dengue virus (DENV). Rapid and reliable diagnosis of DENV infection is urgently needed in dengue-endemic regions. We describe here the performance evaluation of the CE-marked VIDAS® dengue immunoassays developed for the automated detection of DENV NS1 antigen and anti-DENV IgM and IgG antibodies. A multicenter concordance study was conducted in 1296 patients from dengue-endemic regions in Asia, Latin America, and Africa. VIDAS® dengue results were compared to those of competitor enzyme-linked immunosorbent assays (ELISA). The VIDAS® dengue assays showed high precision (CV ≤ 10.7%) and limited cross-reactivity (≤15.4%) with other infections. VIDAS® DENGUE NS1 Ag showed high positive and negative percent agreement (92.8% PPA and 91.7% NPA) in acute patients within 0-5 days of symptom onset. VIDAS® Anti-DENGUE IgM and IgG showed a moderate-to-high concordance with ELISA (74.8% to 90.6%) in post-acute and recovery patients. PPA was further improved in combined VIDAS® NS1/IgM (96.4% in 0-5 days acute patients) and IgM/IgG (91.9% in post-acute patients) tests. Altogether, the VIDAS® dengue NS1, IgM, and IgG assays performed well, either alone or in combination, and should be suitable for the accurate diagnosis of DENV infection in dengue-endemic regions.

Repellent Screening of Selected Plant Essential Oils Against Dengue Fever Mosquitoes Using Behavior Bioassays

Among the efforts to reduce mosquito-transmitted diseases, such as malaria and dengue fever, essential oils (EOs) have become increasingly popular as natural replacements for the repellant DEET. In this study, seven commercially available plant EOs against Aedes species mosquitoes were evaluated for their complete protection time (CPT, min) in vivo using human-hand in cage tests (GB2009/China and WHO2009). Among the EOs with the highest efficacy in repelling mosquitoes, Aedes albopictus (Skuse) were clove bud oil and patchouli oil. Both were further assessed according to the in vivo method recommended by the WHO, to determine their minimum effective dose and CPT. A comparison of the ED50 values (dose yielding a 50% repellent response) of these two EOs against Aedes aegypti(L.) showed that the ED50 (2.496 µg/cm2) of patchouli oil was 1248 times higher than that of clove bud oil (0.002 µg/cm2), thus demonstrating them greater efficacy of the latter in repelling Ae. aegypti mosquitoes. For the 2 EOs, eugenol was the major component with higher than 80% in relative amount of the clove bud oil. The patchouli oil had more than 30% of character chemical patchouli alcohol along with α-bulnesene (10.962%), α-guaiene (9.227%), and seychellene (7.566%). Clove bud oil was found to confer longer complete protection than patchouli oil against a common species of mosquito. These results suggest use of EOs as safe, highly potent repellents for use in daily life and against mosquito-transmitted diseases, such as malaria and dengue fever.

Evaluation of an Immunoglobulin E Capture Enzyme-Linked Immunosorbent Assay for the Early Diagnosis of Dengue.

Dengue virus (DENV) is the etiological agent of dengue, the most important mosquito-transmitted viral disease of humans worldwide. Enzyme-linked immunosorbent assays (ELISAs) designed to detect DENV IgM are commonly used for dengue diagnosis. However, DENV IgM is not reliably detected until ≥4 days after illness onset. Reverse transcription-polymerase chain reaction (RT-PCR) can diagnose early dengue but requires specialized equipment, reagents, and trained personnel. Additional diagnostic tools are needed. Limited work has been performed to determine whether IgE-based assays can be used for the early detection of vector-borne viral diseases, including dengue. In this study, we determined the efficacy of a DENV IgE capture ELISA for the detection of early dengue. Sera were collected within the first 4 days of illness onset from 117 patients with laboratory-confirmed dengue, as determined by DENV-specific RT-PCR. The serotypes responsible for the infections were DENV-1 and DENV-2 (57 and 60 patients, respectively). Sera were also collected from 113 dengue-negative individuals with febrile illness of undetermined etiology and 30 healthy controls. The capture ELISA detected DENV IgE in 97 (82.9%) confirmed dengue patients and none of the healthy controls. There was a high false positivity rate (22.1%) among the febrile non-dengue patients. In conclusion, we provide evidence that IgE capture assays have the potential to be explored for early diagnosis of dengue, but further research is necessary to address the possible false positivity rate among patients with other febrile illnesses.

Artificial intelligence (AI): a new window to revamp the vector-borne disease control.

Artificial intelligence (AI) facilitates scientists to devise intelligent machines that work and behave like humans to resolve difficulties and problems by utilizing minimal resources. The Healthcare sector has benefited due to this. Mosquito-transmitted diseases pose a significant health risk. Despite all advances, present strategies for curbing these diseases still depend largely on controlling the mosquito vectors. This strategy demands an army of entomology experts for thorough monitoring, determining, and finally eradicating the targeted mosquito population. Deep learning (DL) algorithms may substitute such unmanageable processes. The current review focuses on how AI, with particular emphasis on deep learning, demonstrates effectiveness in quick detection, identification, monitoring, and finally controlling the target mosquito populations with minimal resources. It accelerates the pace of operation and data exploration on ongoing evolutionary status, tendency to feed blood, and age grading of mosquitoes. The successful combination of computer and biological sciences will provide practical insight and generate a new research niche in this study area.

Development of Antibody-Based Therapeutics Against West Nile Virus in Plants.

Since its discovery in 1937 in the West Nile district of Uganda, West Nile virus (WNV) has been one of the leading causes of mosquito-transmitted infectious diseases (Smithburn, Burke, Am J Trop Med 20:22, 1940). Subsequently, it spread to Europe, Asia, Australia, and finally North America in 1999 (Sejvar, Ochsner 5(3):6-10, 2003). Worldwide outbreaks have continued to increase since the 1990s (Chancey et al, Biomed Res Int 2015:376230, 2015). According to the Center for Disease Control and Prevention, more than 51,000 cases of WNV infection and nearly 2400 cases of WNV-related death were reported in the USA from 1999 to 2019. The estimated economic impact of WNV infections is close to 800 million dollars in the USA from 1999 to 2012 (Barrett, Am J Trop Med Hyg 90:389, 2014).

Climate-driven mosquito-borne viral suitability index: measuring risk transmission of dengue, chikungunya and Zika in Mexico

BackgroundClimate variability influences the population dynamics of the Aedes aegypti mosquito that transmits the viruses that cause dengue, chikungunya and Zika. In recent years these diseases have grown considerably. Dengue is now the fastest-growing mosquito-transmitted disease worldwide, putting 40 per cent of the global population at risk. With no effective antiviral treatments or vaccines widely available, controlling mosquito population remains one of the most effective ways to prevent epidemics. This paper analyses the temporal and spatial dynamics of dengue in Mexico during 2000–2020 and that of chikungunya and Zika since they first appeared in the country in 2014 and 2015, respectively. This study aims to evaluate how seasonal climatological variability affects the potential risk of transmission of these mosquito-borne diseases. Mexico is among the world’s most endemic countries in terms of dengue. Given its high incidence of other mosquito-borne diseases and its size and wide range of climates, it is a good case study.MethodsWe estimate the recently proposed mosquito-borne viral suitability index P, which measures the transmission potential of mosquito-borne pathogens. This index mathematically models how humidity, temperature and precipitation affect the number of new infections generated by a single infected adult female mosquito in a host population. We estimate this suitability index across all Mexico, at small-area level, on a daily basis during 2000–2020.ResultsWe find that the index P predicted risk transmission is strongly correlated with the areas and seasons with a high incidence of dengue within the country. This correlation is also high enough for chikungunya and Zika in Mexico. We also show the index P is sensitive to seasonal climatological variability, including extreme weather shocks.ConclusionsThe paper shows the dynamics of dengue, chikungunya and Zika in Mexico are strongly associated with seasonal climatological variability and the index P. This potential risk of transmission index, therefore, is a valuable tool for surveillance for mosquito-borne diseases, particularly in settings with varied climates and limited entomological capacity.

Externalities modulate the effectiveness of the Wolbachia release programme

Externalities modulate the effectiveness of the Wolbachia release programme

Geographical clusters of dengue outbreak in Singapore during the Covid-19 nationwide lockdown of 2020

Dengue, a mosquito-transmitted viral disease, has posed a public health challenge to Singaporean residents over the years. In 2020, Singapore experienced an unprecedented dengue outbreak. We collected a dataset of geographical dengue clusters reported by the National Environment Agency (NEA) from 15 February to 9 July in 2020, covering the nationwide lockdown associated with Covid-19 during the period from 7 April to 1 June. NEA regularly updates the dengue clusters during which an infected person may be tagged to one cluster based on the most probable infection location (residential apartment or workplace address), which is further matched to fine-grained spatial units with an average coverage of about 1.35 km2. Such dengue cluster dataset helps not only reveal the dengue transmission patterns, but also reflect the effects of lockdown on dengue spreading dynamics. The resulting data records are released in simple formats for easy access to facilitate studies on dengue epidemics.