Dataset Information

Identifying urban hotspots of dengue, chikungunya, and Zika transmission in Mexico to support risk stratification efforts: a spatial analysis.

ABSTRACT:

Background

Effective Aedes aegypti control is limited, in part, by the difficulty in achieving sufficient intervention coverage. To maximise the effect of vector control, areas with persistently high numbers of Aedes-borne disease cases could be identified and prioritised for preventive interventions. We aimed to identify persistent Aedes-borne disease hotspots in cities across southern Mexico.

Methods

In this spatial analysis, geocoded cases of dengue, chikungunya, and Zika from nine endemic Mexican cities were aggregated at the census-tract level. We included cities that were located in southern Mexico (the arbovirus endemic region of Mexico), with a high burden of dengue cases (ie, more than 5000 cases reported during a 10-year period), and listed as high priority for the Mexican dengue control and prevention programme. The Getis-Ord Gi*(d) statistic was applied to yearly slices of the dataset to identify spatial hotspots of each disease in each city. We used Kendall's W coefficient to quantify the agreement in the distribution of each virus.

Findings

128 507 dengue, 4752 chikungunya and 25 755 Zika clinical cases were reported between Jan 1, 2008, and Dec 31, 2016. All cities showed evidence of transmission heterogeneity, with a mean of 17·6% (SD 4·7) of their total area identified as persistent disease hotspots. Hotspots accounted for 25·6% (SD 9·7; range 12·8-43·0) of the population and 32·1% (10·5; 19·6-50·5) of all Aedes-borne disease cases reported. We found an overlap between hotspots of 61·7% for dengue and Zika and 53·3% for dengue and chikungunya. Dengue hotspots in 2008-16 were significantly associated with dengue hotspots detected during 2017-20 in five of the nine cities. Heads of vector control confirmed hotspot areas as problem zones for arbovirus transmission.

Interpretation

This study provides evidence of the overlap of Aedes-borne diseases within geographical hotspots and a methodological framework for the stratification of arbovirus transmission risk within urban areas, which can guide the implementation of surveillance and vector control.

Funding

USAID, the US Centers for Disease Control and Prevention, the Canadian Institutes of Health Research, International Development Research Centre, Fondo Mixto CONACyT (Mexico)-Gobierno del Estado de Yucatan, and the US National Institutes of Health.

Translation

For the Spanish translation of the abstract see Supplementary Materials section.

SUBMITTER: Dzul-Manzanilla F

PROVIDER: S-EPMC8114339 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Similar Datasets

Project description: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.

Project description:Dengue viruses are the most important arboviral pathogens in the world, which have adapted to human transmission and replication over several hundred years and were initially recognized to cause outbreaks of clinical disease in tropical and subtropical countries by Aedes aegypti mosquitoes. Subsequent global expansion of dengue infection outbreaks has occurred, with millions of cases yearly, probably from a combination of factors including proliferation of international travel and trade, possibly global climate changes, adaptation of the vectors to new environment, and emergence of a new mosquito vector, Aedes albopictus. Chikungunya virus, also transmitted by Aedes mosquitoes, causes a very similar clinical disease but with more prominent arthralgia or arthritis and was originally described in Africa in the 1960s. After a quiescent period of several decades, it reemerged in Africa in 2004 and rapidly spread across the Indian Ocean to involve Asian countries and parts of Europe. However, the past 2 years have seen the emergence of chikungunya virus in the western hemisphere with major outbreaks in the Caribbean and the Americas. Similar to dengue virus, chikungunya virus has adapted to Ae. albopictus mosquitoes which can transmit the disease. Although dengue infection is a more deadly disease especially in young children, chikungunya infection can cause prolonged severe disability and occasionally rare fatalities from encephalitis. No specific treatment is available for either diseases, but development of an effective vaccine for dengue infection is in progress. Until 2007, Zika virus [also transmitted by Aedes species] was associated with only sporadic mild infections in Africa and Asia. In 2007, Zika virus for the first time caused an outbreak beyond Africa and Asia to the Yap Island in the Federated States of Micronesia. Since then Zika virus has spread to French Polynesia, New Caledonia, Cook Islands, and Easter Island in the southeastern Pacific Ocean [Chile] in 2014 and by 2015 to Brazil. By January 2016, it became evident that Zika virus had caused an explosive outbreak in the Americas and the Caribbean with over 30 countries affected. On February 1, 2016, the World Health Organization declared Zika outbreak a global public health emergency. Zika virus infection is most commonly asymptomatic, and 20% of patients may develop a mild viral disease, but of major concern is the reported association of microcephaly in infected pregnant women in Brazil. This chapter explores the history, epidemiology, pathogenesis, clinical features, treatment, and prevention of these rapidly emerging zoonoses.

Project description:BackgroundLow-income urban communities in the tropics often lack sanitary infrastructure and are overcrowded, favoring Aedes aegypti proliferation and arboviral transmission. However, as Ae. aegypti density is not spatially homogeneous, understanding the role of specific environmental characteristics in determining vector distribution is critical for planning control interventions. The objectives of this study were to identify the main habitat types for Ae. Aegypti, assess their spatial densities to identify major hotspots of arbovirus transmission over time and investigate underlying factors in a low-income urban community in Salvador, Brazil. We also tested the field-collected mosquitoes for arboviruses.MethodsA series of four entomological and socio-environmental surveys was conducted in a random sample of 149 households and their surroundings between September 2019 and April 2021. The surveys included searching for potential breeding sites (water-containing habitats) and for Ae. aegypti immatures in them, capturing adult mosquitoes and installing ovitraps. The spatial distribution of Ae. aegypti density indices were plotted using kernel density-ratio maps, and the spatial autocorrelation was assessed for each index. Visual differences on the spatial distribution of the Ae. aegypti hotspots were compared over time. The association of entomological findings with socio-ecological characteristics was examined. Pools of female Ae. aegypti were tested for dengue, Zika and chikungunya virus infection.ResultsOverall, 316 potential breeding sites were found within the study households and 186 in the surrounding public spaces. Of these, 18 (5.7%) and 7 (3.7%) harbored a total of 595 and 283 Ae. aegypti immatures, respectively. The most productive breeding sites were water storage containers within the households and puddles and waste materials in public areas. Potential breeding sites without cover, surrounded by vegetation and containing organic matter were significantly associated with the presence of immatures, as were households that had water storage containers. None of the entomological indices, whether based on immatures, eggs or adults, detected a consistent pattern of vector clustering in the same areas over time. All the mosquito pools were negative for the tested arboviruses.ConclusionsThis low-income community displayed high diversity of Ae. aegypti habitats and a high degree of heterogeneity of vector abundance in both space and time, a scenario that likely reflects other low-income communities. Improving basic sanitation in low-income urban communities through the regular water supply, proper management of solid wastes and drainage may reduce water storage and the formation of puddles, minimizing opportunities for Ae. aegypti proliferation in such settings.