Murine typhus and other potentially lethal rickettsial diseases in Chiapas, Mexico.

Not available.

Procesos celulares modificados en Aedes aegypti infectados con Wolbachia y la susceptibilidad al virus dengue.

OBJETIVO: Analizar la expresión diferencial de proteínas de Aedes aegypti infectados con Wolbachia y su asociación con el ciclo viral del virus dengue (DENV). Material y métodos. Se revisó una base de datos de proteínas de Ae. aegypti infec-tados y no infectados con Wolbachia, cepa wMel y se buscaron estas en revistas indizadas, que hablaran de la proteína y el ciclo viral de DENV. RESULTADOS: La expresión diferencial de proteínas de los mosquitos durante la infección con Wolbachia intervienen en los procesos de entrada, replicación y salida del DENV. CONCLUSIONES: Existen cambios en la expresión de proteínas de células infectadas con Wolbachia, que son necesarias para el ciclo de replicación de DENV, explicando porque algunos mosquitos infectados con Wolbachia son refractarios a la infección por DENV.

Evidencia molecular de Rickettsia ricketsii y Rickettsia felis en garrapatas colectadas en ganado bovino en la costa de Chiapas.

OBJETIVO: Estimar la diversidad de garrapatas, la prevalencia de infestación y tasa de infección de Rickettsia spp. en ganado bovino en la costa del estado de Chiapas. Material y métodos. Se realizó un estudio transversal de octubre de 2021 a marzo de 2022, que incluyó la extracción de garrapatas de 297 vacas pertenecientes a 5 municipios. Se calcularon los índices de diversidad. El diagnóstico de Rickettsia spp en las garrapatas se realizó mediante PCR anida. RESULTADOS: Se encontró una baja diversidad de especies. Las especies Rhipicephalus microplus, Amblyomma cajennense y Rhipicephalus sanguineus hembra adultas fueron positivas a Rickettsia spp. Los municipios de Pijijiapan y Tonalá presentaron la TMI más alta con 7.5 y 7.2%. Conclusión. Este es primer estudio México que reporta infección de Rickettsia spp, en garrapatas colectadas de ganado bovino, lo cual indica un riesgo de salud pública.

Entomopathogenic fungi for the control of larvae and adults of Aedes aegypti (Diptera: Culicidae) vector of dengue, chikungunya and Zika viruses in Mexico.

OBJECTIVE: To assess larvicide and adulticide activity of different native strains of fungi on Aedes aegypti. MATERIALS AND METHODS: Third instar larvae were exposed for 72 h at a concentration of 1x108 conidia/ml of 15 fungi; only fungi that significantly affected the larvae were evaluated against the adult phase at a concentration of 2x1010 conidia/ml. Mortality readings were performed at 24, 48, and 72 h for larvae, and every day to 30 days for adults. RESULTS: Trichoderma longibrachiatum, Aspergillus aculeatus, and Metarhizium anisopliae had the best larvicidal activity at 24 h of exposure (p<0.05), causing mortalities of 100, 72, and 62%, respectively. Adult mosquitoes were more affected by Gliocladium virens (45% mortality), M. anisopliae (30% mortality), and T. longibrachiatum (23.33% mortality). CONCLUSION: The larval stage of Ae. aegypti was more susceptible than the adult phase to the pathogenic action of native fungi, with T. longibrachiatum being with the highest virulence.

Schools as centers for health educational initiatives, health behavior research and risk behavior for dengue infection in school children and community members: a systematic review.

Dengue virus is the main arboviral disease transmitted by Aedes mosquitoes and affects mainly school-aged children and teens. Many methods have been developed for dengue control, including health education strategies for elementary and high school students. The objective of this study is to provide an update on the status of health education on dengue in schools and provide new perspectives on health behavior research in order to reduce the proliferation of mosquitoes and spread of arboviral diseases among school-aged children and other community members. A systematic review about health educational initiatives was carried out. This research discusses the effectiveness of these strategies in educating students about dengue disease and mosquito control and how the school is relevant for community-based participation in research on dengue education. The study found that employing ludic strategies and directly involving children in mosquito control in their households have been the most attractive and effective strategies for dengue education in children and teens. However, the sustainability of protective behaviors has been poorly evaluated, and new approaches for health behavior research are needed. Inasmuch as, schools are important places for gathering community members, and students can serve as an essential link between educative interventions and the community.

Diversity and potential distribution of culicids of medical importance of the Yucatan Peninsula, Mexico.

OBJECTIVE: To determine the species distribution, abundance, and diversity of culicids in the Yucatan Peninsula (YP); their potential distribution, using ecological niche modeling (ENM), and the risk of contact with urban and rural populations. MATERIALS AND METHODS: A cross-sectional study was carried out through the YP. The diversity of species was determined with the Shannon index. The potential distribution of the culicids was determined through the ENM, as well as the risk of urban and rural populations through contact with vectors. RESULTS: A total of 10 699 specimens, 15 genera and 52 species were registered. Campeche and the Biosphere Reserve of Calakmul exhibited the highest diversity. CONCLUSIONS: The ENM predict a high suitability in all the YP of Ae. aegypti, An. albimanus, An. pseudopuntipennis, Cx. coronator, and Cx. quinquefasciatus. The vector species that exhibited the highest risk of contact in the YP were Cx. quinquefasciatus, Ae. aegypti and Ae. albopictus.

OBJETIVO: Determinar la distribución, abundancia y diversidad de los culícidos de la Península de Yucatán (PY), su distribución potencial utilizando modelos de nicho ecológico (MNE) y el riesgo de contacto con poblaciones urbanas y rurales. MATERIAL Y MÉTODOS: Se realizó un estudio transversal. La diversidad fue determinada por el índice de Shannon. La distribución potencial de los culícidos se determinó a través de MNE, así como el riesgo de las poblaciones urbanas y rurales al contacto con los vectores. RESULTADOS: En total, se registraron 10 699 especímenes, 15 géneros y 52 especies. Campeche y la Reserva de la Biosfera de Calakmul presentaron la mayor diversidad. CONCLUSIONES: El MNE predice una alta idoneidad en toda la PY para Ae. aegypti, An. albimanus, An. pseudopuntipennis, Cx. coronador y Cx. quinquefasciatus. Las especies de vectores que presentaron el mayor riesgo de contacto en la PY fueron Cx. quinquefasciatus, Ae. aegypti y Ae. albopictus.

[Indoor thermal fogging of the mixture of flupyradifurone and transflutrin on Aedes aegypti mosquitoes susceptible and resistant to pyrethroids in southern Mexico]. / Nebulización térmica intradomiciliar de la mezcla de flupyradifurona y transflutrina en mosquitos Aedes aegypti susceptibles y resistentes a piretroides en el Sur de México.

OBJECTIVE: To evaluate the efficacy of thermal fogging of a mixture of flupyrafirudone (26.3 g/L) and transfluthrin (52.5 g/L) against dengue, Zika y chikungunya Aedes mosquito vectors. MATERIALS AND METHODS: Groups of 15 caged Ae. aegypti (susceptible and pyrethroid resistant) mosquitoes were placed in living room, kitchen and bedroom inside houses, after which a dose of 2 and 4 mg/m3 of flupyradifurone and transfluthrine, respectively, was applied as thermal fog. After one hour of exposure mosquitoes were transferred to the laboratory and mortality was recorded after 24 h. RESULTS: The mixture killed 97 to 100% of mosquitoes from the strains and the efficacy was similar independently of their place within the premises. CONCLUSIONS: The mixture of flupyrafirudone and transfluthrin applied as thermal fog is a promising tool to control Aedes mosquito populations independently of the pyrethroid-insecticide resistance status.

OBJETIVO: Evaluar la efectividad de la mezcla de flupyradifurona 26.3 g/L y transflutrina 52.5 g/L aplicada como niebla térmica a mosquitos Aedes vectores de virus dengue, Zika y chikungunya. MATERIAL Y MÉTODOS: Se colocaron grupos de 15 mosquitos de Ae. aegypti (susceptibles y resistentes a piretroides) dentro de jaulas, en sala, recámara y cocina. Posteriormente, se aplicó la mezcla de flupyradifurona y transflutrina dentro de las viviendas a una dosis de 2 y 4 mg/m3, respectivamente. RESULTADOS: La mezcla de flupyradifurona y transflutrina causó mortalidades de 97 a 100% sobre las cepas de mosquitos Aedes y su efectividad fue la misma en los diferentes compartimentos de las viviendas. CONCLUSIONES: La mezcla de flupyradifurona y transflutrina, aplicada en niebla térmica, es una herramienta prometedora para el control de poblaciones de mosquitos Aedes independientemente de su estado de resistencia a insecticidas.

Vertical transmission of dengue virus in Aedes aegypti and its role in the epidemiological persistence of dengue in Central and Southern Mexico.

BACKGROUND: Aedes aegypti and Aedes albopictus are the main mosquito species responsible for dengue virus (DENV) transmission to humans in the tropical and subtropical regions of the world. The role of vertical transmission in the epidemiology of dengue and the maintenance of this arbovirus in nature during interepidemic periods remain poorly understood, and DENV vertical transmission could sustain the existence of virus reservoirs within Aedes populations. METHODS: Between April 2011 and October 2012, we monitored vertical transmission of DENV in Ae. aegypti and Ae. albopictus in 9 cities of 4 Mexican states. Aedes eggs were collected in ovitraps, then adults were reared under laboratory conditions and their heads were used to infect C6/36 cells. The presence of flavivirus was detected by immunofluorescence assays (IFA), and DENV infection was confirmed by RT-PCR. RESULTS: About 96% of reared adults were Ae. aegypti and 4.0% were Ae. albopictus. No infection was detected in Ae. albopictus, whereas 54 of 713 (7.8%) of Ae. aegypti pools tested positive. A minimum infection rate (MIR) of 2.52 per 1000 mosquitoes was estimated for Ae. aegypti. DENV-1, DENV-2 & DENV-3 serotypes were detected even during interepidemic periods. CONCLUSIONS: This study reports the evidence of vertical transmission of dengue virus with viral isolation and molecular confirmation in Ae. aegypti eggs collected in four endemic regions of Central and Southern Mexico. Vertical transmission may play a role as a reservoir mechanism during mosquito dormancy in interepidemic periods but with minor participation in transmission during epidemic periods.

TRANSMISSION VERTICALE DU VIRUS DE LA DENGUE CHEZ AEDES AEGYPTI ET SON RÔLE DANS LA PERSISTANCE ÉPIDÉMIOLOGIQUE DE LA DENGUE DANS LE CENTRE ET LE SUD DU MEXIQUE: OBJECTIF: Aedes aegypti et Aedes albopictus sont les principales espèces de moustiques responsables de la transmission du virus de la dengue (DENV) à l'homme dans les régions tropicales et subtropicales du monde. Le rôle de la transmission verticale dans l'épidémiologie de la dengue et le maintien de cet arbovirus dans la nature pendant les périodes d'inter-épidémiques restent mal compris, et la transmission verticale du DENV pourrait maintenir l'existence de réservoirs de virus au sein des populations d'Aedes. Notre objectif était d'évaluer la transmission verticale du DENV au Mexique. MÉTHODES: Entre avril 2011 et octobre 2012, nous avons surveillé la transmission verticale du DENV chez Ae. aegypti et Ae. albopictus dans 9 villes de 4 états mexicains. Les œufs d'Aedes ont été collectés dans des ovitraps, puis les adultes ont été élevés dans des conditions de laboratoire et leur tête a été utilisée pour infecter les cellules C6/36. La présence de flavivirus a été détectée par des tests d'immunofluorescence (IFA) et l'infection par DENV a été confirmée par RT-PCR. RÉSULTATS: 96% des adultes élevés étaient Ae. aegypti et 4,0% étaient Ae. albopictus. Aucune infection n'a été détectée chez Ae. albopictus, alors que 54 des 713 (7,8%) des pools d'Ae. aegypti ont été testés positifs. Un taux d'infection minimum (MIR) de 2,52 pour 1000 moustiques a été estimé pour Ae. aegypti. Les sérotypes DENV-1, DENV-2 et DENV-3 ont été détectés même pendant les périodes inter-épidémiques. CONCLUSIONS: Cette étude rapporte les preuves de transmission verticale du virus de la dengue avec isolement viral et confirmation moléculaire dans les œufs d'Ae. Aegypti collectés dans quatre régions d'endémie du centre et du sud du Mexique. La transmission verticale pourrait jouer un rôle de mécanisme réservoir lors de la dormance des moustiques en période inter-épidémique, mais avec une participation mineure à la transmission en période d'épidémie.

Effects of climatic and social factors on dengue incidence in Mexican municipalities in the state of Veracruz.

OBJECTIVE:: To assess links between the social variables and longer-term El Niño-Southern Oscillation (ENSO) related weather conditions as they relate to the week-to-week changes in dengue incidence at a regional level. MATERIALS AND METHODS:: We collected data from 10 municipalities of the Olmeca region in México, over a 10 year period (January 1995 to December 2005). Negative binomial models with distributed lags were adjusted to look for associations between changes in the weekly incidence rate of dengue fever and climate variability. RESULTS:: Our results show that it takes approximately six weeks for sea surface temperatures (SST -34) to affect dengue incidence adjusted by weather and social variables. CONCLUSION:: Such models could be used as early as two months in advance to provide information to decision makers about potential epidemics. Elucidating the effect of climatic variability and social variables, could assist in the development of accurate early warning systems for epidemics like dengue, Chikungunya and Zika.

Outbreak of Zika Virus Infection, Chiapas State, Mexico, 2015, and First Confirmed Transmission by Aedes aegypti Mosquitoes in the Americas.

BACKGROUND: After decades of obscurity, Zika virus (ZIKV) has spread through the Americas since 2015 accompanied by congenital microcephaly and Guillain-Barré syndrome. Although these epidemics presumably involve transmission by Aedes aegypti, no direct evidence of vector involvement has been reported, prompting speculation that other mosquitoes such as Culex quinquefasciatus could be involved. METHODS: We detected an outbreak of ZIKV infection in southern Mexico in late 2015. Sera from suspected ZIKV-infected patients were analyzed for viral RNA and antibodies. Mosquitoes were collected in and around patient homes and tested for ZIKV. RESULTS: Of 119 suspected ZIKV-infected patients, 25 (21%) were confirmed by RT-PCR of serum collected 1-8 days after the onset of signs and symptoms including rash, arthralgia, headache, pruritus, myalgia, and fever. Of 796 mosquitoes collected, A. aegypti yielded ZIKV detection by RT-PCR in 15 of 55 pools (27.3%). No ZIKV was detected in C. quinquefasciatus ZIKV sequences derived from sera and mosquitoes showed a monophyletic relationship suggestive of a point source introduction from Guatemala. CONCLUSIONS: These results demonstrate the continued, rapid northward progression of ZIKV into North America with typically mild disease manifestations, and implicate A. aegypti for the first time as a principal vector in North America.

Comparison of Climate Change Scenarios of Rhipicephalus sanguineus sensu lato (Latreille 1806) from México and the Boarders with Central America and the United States.

In America, the presence of Rhipicephalus sanguineus sensu stricto and Rhipicephalus linnaei has been confirmed. Both species are found in sympatry in the southern United States, northern Mexico, southern Brazil, and Argentina. The objective of this work is to evaluate the projection of the potential distribution of the ecological niche of Rhipicephalus sanguineus sensu lato in two climate change scenarios in Mexico and the border with Central America and the United States. Initially, a database of personal collections of the authors, GBIF, Institute of Epidemiological Diagnosis and Reference, and scientific articles was built. The ENMs were projected for the current period and two future scenarios: RCP and SSP used for the kuenm R package, the ecological niche of R. sanguineus s.l. It is distributed throughout the Mexico and Texas (United States), along with the border areas between Central America, Mexico, and the United States. Finally, it is observed that the ecological niche of R. sanguineus s.l. in the current period coincides in three degrees with the routes of human migration. Based on this information, and mainly on the flow of migrants from Central America to the United States, the risk of a greater gene flow in this area increases, so the risk relating to this border is a latent point that must be analyzed.

Resistance to Pyrethroids in the Malaria Vector Anopheles albimanus in Two Important Villages in the Soconusco Region of Chiapas, Mexico, 2022.

Chiapas State comprises the largest malaria foci from Mexico, and 57% of the autochthonous cases in 2021, all with Plasmodium vivax infections, were reported in this State. Southern Chiapas is at constant risk of cases imported due to migratory human flow. Since chemical control of vector mosquitoes is the main entomological action implemented for the prevention and control of vector-borne diseases, this work aimed to investigate the susceptibility of Anopheles albimanus to insecticides. To this end, mosquitoes were collected in cattle in two villages in southern Chiapas in July-August 2022. Two methods were used to evaluate the susceptibility: the WHO tube bioassay and the CDC bottle bioassay. For the latter, diagnostic concentrations were calculated. The enzymatic resistance mechanisms were also analyzed. CDC diagnostic concentrations were obtained; 0.7 µg/mL deltamethrin, 12 µg/mL permethrin, 14.4 µg/mL malathion, and 2 µg/mL chlorpyrifos. Mosquitoes from Cosalapa and La Victoria were susceptible to organophosphates and to bendiocarb, but resistant to pyrethroids, with mortalities between 89% and 70% (WHO), and 88% and 78% (CDC), for deltamethrin and permethrin, respectively. High esterase levels are suggested as the resistance mechanism involved in the metabolism of pyrethroids in mosquitoes from both villages. Mosquitoes from La Victoria might also involve cytochrome P450. Therefore, organophosphates and carbamates are suggested to currently control An. albimanus. Its use might reduce the frequency of resistance genes to pyrethroids and vector abundance and may impede the transmission of malaria parasites.

Design and Evaluation of a Sticky Attractant Trap for Intra-Domiciliary Surveillance of Aedes aegypti Populations in Mexico.

Surveillance consists of systematic data collection, analysis, and interpretation and is essential for planning and implementing control activities. The lack of success in the control and surveillance of the Ae. aegypti mosquito elsewhere demands the development of new accessible and effective strategies. This work aimed to develop and evaluate an adhesive lure trap for household indoor surveillance of Ae. aegypti. Based on a bibliographic review, four compounds that have significant attraction percentages for Ae. aegypti were considered. Our more effective blend was determined through preliminary bioassays using the high-throughput screening system (HITSS) and 90 × 90 cm mosquito cages. We designed a low-cost, pyramid-shaped, sticky cardboard trap to incorporate the selected blend. Semi-field 2 × 2 m cages and field tests were utilized to evaluate its effectiveness through mosquito capture percentages. In laboratory tests, blend number 2 presented an attraction percentage of 47.5 ± 4.8%; meanwhile, in semi-field cages, a 4-inch, 110 v powered fan was used to disperse the attractants, and then a similar capture percentage of 43.2 ± 4.0% was recorded. Results were recorded during the field evaluation of the at-house indoor environment and were compared with those recorded with the golden-standard BG-Sentinel trap, i.e., our prototype trapped an average of 6.0 ± 1.5 mosquitoes versus 10.0 ± 2.6. In most Latin American countries, there is a lack of formal and accessible strategies for monitoring adult populations of Ae. Aegypti; therefore, we must develop tools that reinforce entomological surveillance methods.

A prospective cohort study to evaluate peridomestic infection as a determinant of dengue transmission: protocol.

BACKGROUND: Vector control programs, which have focused mainly on the patient house and peridomestic areas around dengue cases, have not produced the expected impact on transmission. This project will evaluate the assumption that the endemic/epidemic transmission of dengue begins around peridomestic vicinities of the primary cases. Its objective is to assess the relationship between symptomatic dengue case exposure and peridomestic infection incidence. METHODS/DESIGN: A prospective cohort study will be conducted (in Tepalcingo and Axochiapan, in the state of Morelos, Mexico), using the state surveillance system for the detection of incident cases. Paired blood specimens will be collected from both the individuals who live with the incident cases and a sample of subjects residing within a 25-meter radius of such cases (exposed cohort), in order to measure dengue-specific antibodies. Other subjects will be selected from areas which have not presented any incident cases within 200 meters, during the two months preceding the sampling (non-exposed cohort). Symptomatic/asymptomatic incident infection will be considered as the dependent variable, exposure to confirmed dengue cases, as the principal variable, and the socio-demographic, environmental and socio-cultural conditions of the subjects, as additional explanatory variables. DISCUSSION: Results indicating a high infection rate among the exposed subjects would justify the application of peridomestic control measures and call for an evaluation of alternate causes for insufficient program impact. On the other hand, a low incidence of peridomestic-infected subjects would support the hypothesis that infection occurs outside the domicile, and would thus explain why the vector control measures applied in the past have exerted such a limited impact on cases incidence rates. The results of the present study may therefore serve to reassess site selection for interventions of this type.

[Integrated prevention and control strategy for dengue in Mesoamerica]. / La estrategia para la prevención y el control integrado del dengue en Mesoamérica.

Dengue in the Americas is a public health problem in ascent. The control strategies have not been effective when sustained in the intensive use of insecticides and poor community participation. The Mesoamerican Initiative for the Prevention and the Integrated Control of Dengue synthesizes the works generated by the Integrated Strategy of the Pan-American Health Organization (PAHO) and the risks stratification strategy designed by the countries of the Mesoamerican region. The objective is to progressively reduce the incidence of dengue cases until a 50% reduction is reached over a five years period. This document describes the elements for the risk stratification, the activities for prevention and control organized by levels of intensity and frequency and the indicators used to pursuit the objectives. To face the dispersion of the problem a concentration of efforts for control in the areas of greater risk is presented; the opportunity in the detection of cases is highlighted to tackle the fast dissemination of the infection; focus on the most productive breeding sites is proposed to battle against the vast dissemination of the breeding sites; and the severity of the infection must be addressed by capable clinical human resources. This strategy was designed along with the national representatives of the control programs to create master plans that provided the basis for the integrated prevention and control of dengue in the Mesoamerican region.

[Targeted treatment of Aedes aegypti at localities with high risk for dengue transmission, Morelos, Mexico]. / Control enfocado de Aedes aegypti en localidades de alto riesgo de transmisión de dengue en Morelos, México.

OBJECTIVE: To determine the relative importance of Aedes aegyti breeding sites for potential targeted dengue control interventions in Morelos. MATERIAL AND METHODS: Cross-sectional entomological surveys were conducted and collection of Ae. aegypti pupae was taken from all water-holding containers in Cuautla, Jojutla and Tlaquiltenango during dry (1,713 households) and rainy (1,677) seasons in 2008. Relative importance of different types of breeding sites was determined by the contribution (%) to total pupae production within each locality. RESULTS: In Cuautla most pupae during the dry season were found in wash basins (48.5%), tanks and buckets/pots (15% each); during the rainy season, diverse small items (21.3%), buckets/pots (19.3%) and plant pots (12.9%) were more productive. In Jojutla and Tlaquiltenango, 97% of all pupae was found in plant pots during the dry season; during the rainy season diverse small items (26.3%), washing/cooking utensils (13.9%), buckets/pots (12.9%) and plant pots (12.7%) were significant. CONCLUSION: Prevention and control of the dengue vector should be based on this kind of evidence to target the most productive breeding-sites.

Field Effectiveness of Drones to Identify Potential Aedes aegypti Breeding Sites in Household Environments from Tapachula, a Dengue-Endemic City in Southern Mexico.

Aedes aegypti control programs require more sensitive tools in order to survey domestic and peridomestic larval habitats for dengue and other arbovirus prevention areas. As a consequence of the COVID-19 pandemic, field technicians have faced a new occupational hazard during their work activities in dengue surveillance and control. Safer strategies to monitor larval populations, in addition to minimum householder contact, are undoubtedly urgently needed. Drones can be part of the solution in urban and rural areas that are dengue-endemic. Throughout this study, the proportion of larvae breeding sites found in the roofs and backyards of houses were assessed using drone images. Concurrently, the traditional ground field technician's surveillance was utilized to sample the same house groups. The results were analyzed in order to compare the effectiveness of both field surveillance approaches. Aerial images of 216 houses from El Vergel village in Tapachula, Chiapas, Mexico, at a height of 30 m, were obtained using a drone. Each household was sampled indoors and outdoors by vector control personnel targeting all the containers that potentially served as Aedes aegypti breeding sites. The main results were that the drone could find 1 container per 2.8 found by ground surveillance; however, containers that were inaccessible by technicians in roofs and backyards, such as plastic buckets and tubs, disposable plastic containers and flowerpots were more often detected by drones than traditional ground surveillance. This new technological approach would undoubtedly improve the surveillance of Aedes aegypti in household environments, and better vector control activities would therefore be achieved in dengue-endemic countries.

Evolution of dengue virus in Mexico is characterized by frequent lineage replacement.

Both dengue fever and its more serious clinical manifestation, dengue hemorrhagic fever, represent major public health concerns in the Americas. To understand the patterns and dynamics of virus transmission in Mexico, a country characterized by a marked increase in dengue incidence in recent years, we undertook a molecular evolutionary analysis of the largest sample of Mexican strains of dengue virus compiled to date. Our E gene data set comprises sequences sampled over a period of 27 years and representing all of the Mexican states that are endemic for dengue. Our phylogenetic analysis reveals that, for each of the four dengue viruses (DENV-1 to DENV-4), there have been multiple introductions of viral lineages in Mexico, with viruses similar to those observed throughout the Americas, but there has been strikingly little co-circulation. Rather, dengue virus evolution in Mexico is typified by frequent lineage replacement, such that only a single viral lineage dominates in a specific serotype at a specific time point. Most lineage replacement events involve members of the same viral genotype, although a replacement event involving different genotypes was observed with DENV-2, and viral lineages that are new to Mexico are described for DENV-1, DENV-3 and DENV-4.