ArboAlvo: stratification method for territorial receptivity to urban arboviruses

Historical Hot Spots of Dengue and Zika Viruses to Guide Targeted Vector Control in San Juan, Puerto Rico (2010-2022)

Dengue viruses (DENV) continue to cause large outbreaks in tropical countries, while chikungunya and Zika (ZIKV) viruses have added complexity to Aedes-borne disease prevention and control efforts. Because these viruses are transmitted by the same vectors in urban areas, it is useful to understand if sequential outbreaks caused by these viruses have commonalities, such as similar seasonal and spatial patterns, that would help anticipate and perhaps prevent future outbreaks. We explored and analyzed the heterogeneity of confirmed cases of DENV (2010-2014 and 2015-2022) and ZIKV (2016-2017) during outbreaks in the San Juan metropolitan area of Puerto Rico to explore their degree of overlap and prioritize areas for Aedes aegypti control. Deidentified, georeferenced case data were aggregated into grid cells (500 × 500 m) within a geographical information system of the study area and analyzed to calculate the degree of overlap between outbreaks. Spatial autocorrelations using local indicators of spatial associations were conducted to identify significant disease case hot spots and correlations between outbreaks. We found that 75% of cases during the three transmission periods were concentrated in 25% of the total number of grid cells covering the study area. We also found significant clustering of cases during each outbreak, enabling identification of consistent disease hot spots. Our results showed 85% spatial overlap between cases of ZIKV in 2015-2017 and DENV in 2010-2014 and 97% overlap between DENV cases in 2010-2014 and 2015-2022. These results reveal urban areas at greater risk of future arbovirus outbreaks that should be prioritized for vector control.

[Stratification of risk areas for measles transmission: a systematic reviewEstratificación de las zonas de riesgo de transmisión del sarampión: revisión sistemática]

Objective

To perform a systematic review of scientific publications addressing the use of stratification methods to define risk areas for measles transmission.

Method

Articles published in English, Portuguese, and Spanish in journals indexed in the SciELO, PubMed, and LILACS databases were selected. The search terms risk assessment AND measles were used without date limits. Editorials, opinion articles, individual-level observational studies, and publications that did not focus on the application of methods to stratify measles transmission risk areas were excluded. Year of publication, authorship, country where the study was performed, objective, geographic level of analysis, method used, indicators, and limitations were recorded in a data form.

Results

Thirteen articles published between 2011 and 2022 in nine countries from the six World Health Organization (WHO) regions were selected. Of these, 10 referred to the Measles Risk Assessment Tool developed by the WHO/Centers for Disease Control and Prevention. Only one study adapted the tool to the local context. The risk stratification indicators used in the selected studies focused on a combination of the following dimensions: population immunity, quality of surveillance systems, and epidemiologic status. The systematic output of data with adequate quality and coverage was a noteworthy aspect hindering risk stratification.

Conclusion

There seems to be limited dissemination of measles risk stratification strategies, especially at local levels. The need to train human resources to process and interpret risk analyses as part of the routine of surveillance services is emphasized.

Assessment of insecticide resistance of Aedes aegypti (Diptera: Culicidae) populations to insect growth regulator pyriproxyfen, in the northeast region of Brazil

Vector control has been an essential strategy in Brazil to manage vector-borne diseases, and the use of insecticides plays an important role in this effort. Pyriproxyfen (PPF) has become a common insect growth regulator used to control juvenile stages of mosquitoes by disturbing their growth and development. This study assesses the susceptibility and resistance status of Brazilian Ae. aegypti populations that previously showed low resistance levels to PPF. Eggs of Ae. aegypti were collected from six cities located in the northeast states of Ceará (Quixadá, Icó, and Juazeiro do Norte), and Bahia (Itabuna, Brumado, and Serrinha). We used the Ae. aegypti Rockefeller strain as an experimental control and a strain known to be susceptible to insecticides. Inhibition of emergence rates by 50% of Ae. aegypti populations varied from 0.0098-0.046 µg/L. Mosquitoes from Icó, Serrinha, and Brumado showed low resistance levels [resistance ratio (RR₅₀) = 2.33, 4.52, and 4.83, respectively], whereas moderate levels of resistance were detected in populations from Juazeiro do Norte (RR₅₀=5.83) and Itabuna (RR₅₀=7.88). Aedes aegypti collected from the Quixadá population showed a high resistance level to pyriproxyfen (RR₅₀=11). The evolution of resistance in Brazilian Ae. aegypti populations to PPF can compromise vector control efforts. Continuous monitoring of insecticide resistance in Ae. aegypti is essential for making timely management decisions for effective vector control and management.