El dengue es la arbovirosis más importante en salud pública. Es transmitido por la picadura de mosquitos hembras de Aedes spp., que se infectan de manera horizontal al ingerir sangre de una persona virémica. Sin embargo, numerosos estudios han identificado la transmisión vertical como otro mecanismo de infección vectorial. Con el propósito de analizar la ocurrencia de transmisión vertical del virus dengue por mosquitos Aedes, se recolectaron mosquitos adultos en viviendas y otras locaciones durante los levantamientos de índices entomológicos realizados por la Secretaría de Salud de Medellín en los años 2016 (epidémico) y 2017 (endémico). Los ejemplares se identificaron y conformaron pools para la detección viral por RT-PCR. En total se recolectaron 6.708 mosquitos, donde, el 96 % y 4 % correspondieron a Ae. aegypti y Ae. albopictus, respectivamente. De los 2.211 pools conformados, 294 resultaron positivos para virus dengue, y 50 de estos correspondieron exclusivamente a machos de Aedes spp. Tanto para el año epidémico como endémico, se registró transmisión vertical, pero fue más frecuente en el 2016. Se observó transmisión vertical en todos los sectores de la ciudad, sin un patrón definido. La presencia de machos Aedes spp. infectados naturalmente con virus dengue sugiere que la transmisión vertical es un evento más frecuente de lo que se consideraba, y podría comprender una mayor relevancia epidemiológica. Estudios adicionales para verificar la capacidad de infección del virus detectado en mosquitos machos y precisar el papel de la transmisión vertical en la incidencia de dengue se hacen necesarios.

Introducción. El dengue en Colombia representa un grave problema de salud y, dado que no existe un tratamiento efectivo para la enfermedad y la vacuna no se ha aprobado en todos los países, se deben fortalecer acciones para mitigar su impacto mediante el control de Aedes aegypti, el mosquito vector. La vigilancia en el país se hace con base en los índices entomológicos y en la notificación de casos, la cual es frecuentemente tardía y por ello conduce a falta de oportunidad en las intervenciones. La detección viral en mosquitos urbanos mediante técnicas moleculares proporciona información entomológica más precisa para la adopción de decisiones.Objetivo. Reportar los resultados de la vigilancia virológica de especímenes de Aedes spp. recolectados durante actividades entomológicas rutinarias de la Secretaría de Salud de Medellín.Materiales y métodos. Los ejemplares se recolectaron durante dos periodos, en cada uno de los cuales se seleccionaron 18 viviendas alrededor de cada una de las 250 trampas para larvas dispuestas para la vigilancia entomológica, así como 70 instituciones educativas y 30 centros de salud. Los ejemplares se identificaron y se conformaron grupos para la detección viral mediante reacción en cadena de la polimerasa con transcripción inversa (Reverse Transcription Polymerase Chain Reaction, RT-PCR). Se calculó la tasa mínima de infección y el índice de infestación en adultos.Resultados. Se recolectaron 1.507 mosquitos, 10 de los cuales eran Ae. albopictus. De los 407 grupos conformados, 132 (uno de ellos de Ae. albopictus) fueron positivos, y 14,39 % correspondió a machos de Ae. aegypti. La tasa mínima de infección para Ae. aegypti fue de 120,07 y 69,50 en el primer y segundo períodos, respectivamente, y el índice de infestación en adultos fue mayor en las instituciones educativas (23,57 %).Conclusión. Mediante la RT-PCR se detectaron la infección natural y la transmisión vertical del virus del dengue en Ae. aegypti y en Ae. albopictus. Se propone considerar la incorporación de estas técnicas moleculares en los programas de vigilancia y control de las arbovirosis en el país.

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Background: Thermal fogging of Insecticides is a vector control strategy used by the Medellin Secretary of Health to combat dengue. This method is employed during outbreaks to curb populations of potentially infectious adult mosquitoes and interrupt transmission cycles. While this strategy has been used in Medellin since 2007, in some years it has not reduced dengue cases as expected. Difficulties in the implementation of fumigation strategies, such as lack of opportunity for treatment and public perception may be factors that limit its utility. The objective of this study was to identify barriers that hinder the implementation of thermal fogging, as well as attitudes and beliefs that prevent its acceptance. Methods: We used a cross-sectional observational study of mixed methods carried out in neighborhoods prioritized for fumigation treatment in Medellin, Colombia. First, we assessed the timeliness of treatment by determining the latency period between reported dengue cases and the implementation of fumigation in response to those cases. Next, we administered structured questionnaires to residents in the area of fumigation treatments (n = 4455 homes) to quantify acceptance and rejection, as well as factors associated with rejection. Results: The median time between notification and treatment was 25 days (IQR 20.0-36.5). Fumigators were only able to treat 53.7% of total households scheduled for treatment; 9.6% rejected treatment, and treatment teams were unable to fumigate the remaining 36.7% of homes due to absent residents, no adults being present, and other reasons. The most frequent causes for rejection were residents being busy at the time of treatment (33.1%) and no interest in the treatment (24.5%). Other reasons for rejection include the perceptions that fumigation does not control pests other than mosquitoes (4.3%), that no mosquitoes were present in the home (3.3%), and that fumigation affects human health (3.1%). Conclusions: The high percentage of houses where it was not possible to perform fumigation limits control of the vector. Future strategies should consider more flexible treatment schedules and incorporate informational messages to educate residents about the safety and importance of treatment.

Surveillance and control activities for virus-transmitting mosquitoes have primarily focused on dwellings. There is little information about viral circulation in heavily trafficked places such as schools. We collected and analyzed data to assess the presence and prevalence of dengue, chikungunya, and Zika viruses in mosquitoes, and measured Aedes indices in schools in Medellín (Colombia) between 2016–2018. In 43.27% of 2632 visits we collected Aedes adults, creating 883 pools analyzed by RT-PCR. 14.27% of pools yielded positive for dengue or Zika (infection rates of 1.75–296.29 for Aedes aegypti). Ae. aegypti was more abundant and had a higher infection rate for all studied diseases. Aedes indices varied over time. There was no association between Aedes abundance and mosquito infection rates, but the latter did correlate with cases of arboviral disease and climate. Results suggest schools are important sources of arbovirus and health agencies should include these sites in surveillance programs; it is essential to know the source for arboviral diseases transmission and the identification of the most population groups exposed to these diseases to research and developing new strategies.

Dengue is a growing global threat in some of the world’s most rapidly growing landscapes. Research shows that urbanization and human movement affect the spatial dynamics and magnitude of dengue outbreaks; however, precise effects of urban growth on dengue are not well understood because of a lack of sufficiently fine-scaled data. We analyzed nine years of address-level dengue case data in Medellin, Colombia during a period of public transit expansion. We correlate changes in the spread and magnitude of localized outbreaks to changes in accessibility and usage of public transit. Locations closer to and with a greater utilization of public transit had greater dengue incidence. This relationship was modulated by socioeconomic status; lower socioeconomic status locations experienced stronger effects of public transit accessibility and usage on dengue incidence. Public transit is a vital urban resource, particularly among low socioeconomic populations. These results highlight the importance of public health services concurrent with urban growth.

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Dengue is a growing global threat in some of the world’s most rapidly growing landscapes. Urbanization and human movement affect the spatial dynamics and magnitude of dengue outbreaks; however, precise effects of urban growth on dengue is not well understood because of a lack of sufficiently fine-scaled data. We analyzed nine years of address-level dengue case data in Medellin, Colombia during a period of public transit expansion. We correlate changes in the spread and magnitude of localized outbreaks to changes in accessibility and usage of public transit. Locations closer to and with a greater utilization of public transit had greater dengue incidence. This relationship was modulated by socioeconomic status; lower socioeconomic status locations experienced stronger effects of public transit accessibility and usage on dengue incidence. Public transit is a vital urban resource, particularly among low socioeconomic populations; these results highlight the importance of public health services concurrent with urban growth.