Mercy J. Borbor-Cordova

Spatiotemporal clustering, climate periodicity, and social-ecological risk factors for dengue during an outbreak in Machala, Ecuador, in 2010

BackgroundDengue fever, a mosquito-borne viral disease, is a rapidly emerging public health problem in Ecuador and throughout the tropics. However, we have a limited understanding of the disease transmission dynamics in these regions. Previous studies in southern coastal Ecuador have demonstrated the potential to develop a dengue early warning system (EWS) that incorporates climate and non-climate information. The objective of this study was to characterize the spatiotemporal dynamics and climatic and social-ecological risk factors associated with the largest dengue epidemic to date in Machala, Ecuador, to inform the development of a dengue EWS.MethodsThe following data from Machala were included in analyses: neighborhood-level georeferenced dengue cases, national census data, and entomological surveillance data from 2010; and time series of weekly dengue cases (aggregated to the city-level) and meteorological data from 2003 to 2012. We applied LISA and Moran’s I to analyze the spatial distribution of the 2010 dengue cases, and developed multivariate logistic regression models through a multi-model selection process to identify census variables and entomological covariates associated with the presence of dengue at the neighborhood level. Using data aggregated at the city-level, we conducted a time-series (wavelet) analysis of weekly climate and dengue incidence (2003-2012) to identify significant time periods (e.g., annual, biannual) when climate co-varied with dengue, and to describe the climate conditions associated with the 2010 outbreak.ResultsWe found significant hotspots of dengue transmission near the center of Machala. The best-fit model to predict the presence of dengue included older age and female gender of the head of the household, greater access to piped water in the home, poor housing condition, and less distance to the central hospital. Wavelet analyses revealed that dengue transmission co-varied with rainfall and minimum temperature at annual and biannual cycles, and we found that anomalously high rainfall and temperatures were associated with the 2010 outbreak.ConclusionsOur findings highlight the importance of geospatial information in dengue surveillance and the potential to develop a climate-driven spatiotemporal prediction model to inform disease prevention and control interventions. This study provides an operational methodological framework that can be applied to understand the drivers of local dengue risk.

Climate services for health: predicting the evolution of the 2016 dengue season in Machala, Ecuador

BACKGROUND El Niño and its effect on local meteorological conditions potentially influences interannual variability in dengue transmission in southern coastal Ecuador. El Oro province is a key dengue surveillance site, due to the high burden of dengue, seasonal transmission, co-circulation of all four dengue serotypes, and the recent introduction of chikungunya and Zika. In this study, we used climate forecasts to predict the evolution of the 2016 dengue season in the city of Machala, following one of the strongest El Niño events on record. METHODS We incorporated precipitation, minimum temperature, and Niño3·4 index forecasts in a Bayesian hierarchical mixed model to predict dengue incidence. The model was initiated on Jan 1, 2016, producing monthly dengue forecasts until November, 2016. We accounted for misreporting of dengue due to the introduction of chikungunya in 2015, by using active surveillance data to correct reported dengue case data from passive surveillance records. We then evaluated the forecast retrospectively with available epidemiological information. FINDINGS The predictions correctly forecast an early peak in dengue incidence in March, 2016, with a 90% chance of exceeding the mean dengue incidence for the previous 5 years. Accounting for the proportion of chikungunya cases that had been incorrectly recorded as dengue in 2015 improved the prediction of the magnitude of dengue incidence in 2016. INTERPRETATION This dengue prediction framework, which uses seasonal climate and El Niño forecasts, allows a prediction to be made at the start of the year for the entire dengue season. Combining active surveillance data with routine dengue reports improved not only model fit and performance, but also the accuracy of benchmark estimates based on historical seasonal averages. This study advances the state-of-the-art of climate services for the health sector, by showing the potential value of incorporating climate information in the public health decision-making process in Ecuador. FUNDING European Union FP7, Royal Society, and National Science Foundation.

Declining Prevalence of Disease Vectors Under Climate Change

More than half of the world population is at risk of vector-borne diseases including dengue fever, chikungunya, zika, yellow fever, leishmaniasis, chagas disease, and malaria, with highest incidences in tropical regions. In Ecuador, vector-borne diseases are present from coastal and Amazonian regions to the Andes Mountains; however, a detailed characterization of the distribution of their vectors has never been carried out. We estimate the distribution of 14 vectors of the above vector-borne diseases under present-day and future climates. Our results consistently suggest that climate warming is likely threatening some vector species with extinction, locally or completely. These results suggest that climate change could reduce the burden of specific vector species. Other vector species are likely to shift and constrain their geographic range to the highlands in Ecuador potentially affecting novel areas and populations. These forecasts show the need for development of early prevention strategies for vector species currently absent in areas projected as suitable under future climate conditions. Informed interventions could reduce the risk of human exposure to vector species with distributional shifts, in response to current and future climate changes. Based on the mixed effects of future climate on human exposure to disease vectors, we argue that research on vector-borne diseases should be cross-scale and include climatic, demographic, and landscape factors, as well as forces facilitating disease transmission at fine scales.

The Social and Spatial Ecology of Dengue Presence and Burden during an Outbreak in Guayaquil, Ecuador, 2012

Dengue fever, a mosquito-borne arbovirus, is a major public health concern in Ecuador. In this study, we aimed to describe the spatial distribution of dengue risk and identify local social-ecological factors associated with an outbreak of dengue fever in the city of Guayaquil, Ecuador. We examined georeferenced dengue cases (n = 4248) and block-level census data variables to identify social-ecological risk factors associated with the presence/absence and burden of dengue in Guayaquil in 2012. Local Indicators of Spatial Association (LISA), specifically Anselin’s Local Moran’s I, and Moran’s I tests were used to locate hotspots of dengue transmission, and multimodel selection was used to identify covariates associated with dengue presence and burden at the census block level. We identified significant dengue transmission hotspots near the North Central and Southern portions of Guayaquil. Significant risk factors for presence of dengue included poor housing conditions, access to paved roads, and receipt of remittances. Counterintuitive positive correlations with dengue presence were observed with several municipal services such as garbage collection and access to piped water. Risk factors for increased burden of dengue included poor housing conditions, garbage collection, receipt of remittances, and sharing a property with more than one household. Social factors such as education and household demographics were negatively correlated with increased dengue burden. These findings elucidate underlying differences with dengue presence versus burden, and suggest that vulnerability and risk maps could be developed to inform dengue prevention and control; this is information that is also relevant for emerging epidemics of chikungunya and Zika viruses.

The high burden of dengue and chikungunya in southern coastal Ecuador: Epidemiology, clinical presentation, and phylogenetics from a prospective study in Machala in 2014 and 2015

Background Dengue (DENV), chikugunya (CHIKV) and zika (ZIKV) viruses are arboviruses transmitted by the Ae. aegypti mosquito, that cause febrile illness and present a major public health challenge in tropical low– and middle-income countries such as Ecuador. Here we report the methods and findings from the first two years (January 1, 2014 to December 31, 2015) of an active and passive surveillance study conducted in the southern coastal city of Machala, Ecuador. Methods Individuals whom presented at one of four sentinel clinics or the central hospital of the Ministry of Health with suspected DENV (index cases) were recruited into the study (n = 324). Index cases with confirmed acute DENV infection triggered a cluster investigation (n = 44) of DENV infections in the index household and four neighboring households (associates) within 200 meters, (n = 397). We conducted genomic sequencing and phylogenetic analysis of select DENV positive samples from 2014. Results In 2014, 72.5% of index patients and 35.6% of associates had evidence of acute or recent DENV infections. In 2015, 28.3% and 12.85% of index patients and associates, respectively, had acute or recent infections. The first cases of CHIKV were detected in an associate on epidemiological week 12 in 2015. There were a total of 54 cases of acute CHIKV infections, including seven DENV/CHIKV co-infections. No cases of ZIKV were detected. DENV symptoms varied significantly by age and by primary versus secondary infections. Symptoms that were associated with DENV and CHIKV infections are presented. Phylogenetic analyses of isolates revealed genetic relatedness and shared ancestry of DENV1, DENV2 and DENV4 genomes from Ecuador with those from Venezuela and Colombia, as well as more than one introduction of the same serotype into Ecuador, indicating presence of viral flow between Ecuador and the surrounding countries. Discussion Findings from this study highlight the importance of (1) implementing rapid active surveillance protocols and (2) strengthening local molecular diagnostic capacities in resource-limited settings where DENV, CHIKV, and ZIKV co-circulate.

Climate Variability, Vulnerability, and Natural Disasters: A Case Study of Zika Virus in Manabi, Ecuador Following the 2016 Earthquake

Abstract Climate change presents complex and wide‐reaching threats to human health. A variable and changing climate can amplify and unmask ecological and socio‐political weaknesses and increase the risk of adverse health outcomes in socially vulnerable regions. When natural disasters occur in such areas, underlying climatic conditions may amplify the public health crisis. We describe an emerging epidemic of Zika virus (ZIKV) in Ecuador following the 2016 earthquake, which coincided with an exceptionally strong El Niño event. We hypothesize that the trigger of a natural disaster during anomalous climate conditions and underlying social vulnerabilities were force multipliers contributing to a dramatic increase in ZIKV cases postearthquake.

The Carbon Holdings of Northern Ecuador's Mangrove Forests

Within a geographic information systems environment, we combine field measures of mangrove tree diameter, mangrove species distribution, and mangrove tree density with remotely sensed measures of mangrove location and mangrove canopy cover to estimate the mangrove carbon holdings of northern Ecuador. We find that the four northern estuaries of Ecuador contain approximately 7,742,999 t (±15.47 percent) of standing carbon. Of particularly high carbon holdings are the Rhizophora mangle–dominated mangrove stands found in and around the Cayapas-Mataje Ecological Reserve in northern Esmeraldas Province, Ecuador, and certain stands of Rhizophora mangle in and around the Isla Corazón y Fragata Wildlife Refuge in central Manabí Province, Ecuador. Our field-driven mangrove carbon estimate is higher than all but one of the comparison models evaluated. We find that basic latitudinal mangrove carbon models performed at least as well, if not better, than the more complex species-based allometric models in predicting standing carbon levels. In addition, we find that improved results occur when multiple models are combined as opposed to relying on any one single model for mangrove carbon estimates. The high level of carbon contained in these mangrove forests, combined with the future atmospheric carbon sequestration potential they offer, makes it a necessity that they are included in any future payment for ecosystem services strategy aimed at using forest systems to offset CO2 emissions and mitigate predicted CO2-driven temperature increases.

Zika Virus Outbreak, Barbados, 2015–2016

Abstract. Barbados is a Caribbean island country of approximately 285,000 people, with a thriving tourism industry. In 2015, Zika spread rapidly throughout the Americas, and its proliferation through the Caribbean islands followed suit. Barbados reported its first confirmed autochthonous Zika transmission to the Pan American Health Organization in January 2016, a month before the global public health emergency was declared. After detection of suspected Zika cases on Barbados in 2015, 926 individuals were described as suspected cases, and 147 laboratory-confirmed cases were reported through December 2016, the end of the most recent epidemiological year. In this short report, we describe the epidemiological characteristics of 926 clinical case records that were originally suspected as cases of Zika, and which were subsequently sent for testing and confirmation; 147 were found positive for Zika, using reverse transcription-polymerase chain reaction methods, another 276 tested negative, and the remaining 503 were either pending results or still in the suspected category. Women were represented at about twice the rate of men in case records where gender was reported (71.9%), and confirmed cases (78.2%), and 19 of the confirmed positive cases were children under the age of 10.

The Burden of Dengue Fever and Chikungunya in Southern Coastal Ecuador: Epidemiology, Clinical Presentation, and Phylogenetics from the First Two Years of a Prospective Study

Abstract. Here, we report the findings from the first 2 years (2014–2015) of an arbovirus surveillance study conducted in Machala, Ecuador, a dengue-endemic region. Patients with suspected dengue virus (DENV) infections (index cases, N = 324) were referred from five Ministry of Health clinical sites. A subset of DENV-positive index cases (N = 44) were selected, and individuals from the index household and four neighboring homes within 200 m were recruited (N = 400). Individuals who entered the study, other than the index cases, are referred to as associates. In 2014, 70.9% of index cases and 35.6% of associates had acute or recent DENV infections. In 2015, 28.3% of index cases and 12.8% of associates had acute or recent DENV infections. For every DENV infection captured by passive surveillance, we detected an additional three acute or recent DENV infections in associates. Of associates with acute DENV infections, 68% reported dengue-like symptoms, with the highest prevalence of symptomatic acute infections in children aged less than 10 years. The first chikungunya virus (CHIKV) infections were detected on epidemiological week 12 in 2015; 43.1% of index cases and 3.5% of associates had acute CHIKV infections. No Zika virus infections were detected. Phylogenetic analyses of isolates of DENV from 2014 revealed genetic relatedness and shared ancestry of DENV1, DENV2, and DENV4 genomes from Ecuador with those from Venezuela and Colombia, indicating the presence of viral flow between Ecuador and surrounding countries. Enhanced surveillance studies, such as this, provide high-resolution data on symptomatic and inapparent infections across the population.

Dengue fever and Aedes aegypti risk in the Galápagos Islands, Ecuador

Introduction Dengue fever is an emerging infectious disease in the Galápagos Islands of Ecuador, with the first cases reported in 2002 and periodic outbreaks since then. Here we report the results of a pilot study conducted in two cities in 2014: Puerto Ayora (PA) on Santa Cruz Island, and Puerto Baquerizo Moreno (PB) on Santa Cristobal Island. The aims of this study were to assess the social-ecological risk factors associated with dengue and mosquito presence at the household-level. Methods In 2014 we conducted 100 household surveys (50 on each island) in neighborhoods with prior reported dengue. Adult mosquitoes were collected inside and outside the home, larval indices were determined through container surveys, and heads of households were interviewed to determine demographics, prior dengue infections, housing conditions, and knowledge, attitudes and practices regarding dengue. Multimodel selection methods were used to derive best-fit generalized linear regression (GLM) models of prior dengue infection, and the presence of Ae. aegypti in the home. Results We found that 24% of PB and 14% of PA respondents self-reported a prior dengue infection, and more PB homes than PA homes had Ae. aegypti. The top-ranked model for prior dengue infection included human movement – travel between neighborhoods, between islands, and to the mainland; demographics including salary level and education of the head of household, and increase with more people per room in a house, house condition, access to water quality issues, and dengue awareness. The top-ranked model for the presence of Ae. aegypti included housing conditions, including the presence of window screens and air conditioners, mosquito control actions, and dengue risk perception. Discussion/conclusion To our knowledge, this is the first study of dengue risk and Aedes aegypti in the Galápagos Islands. The findings that human movement within and between islands, and to and from the mainland, were important to reported dengue cases confirms concerns of this route of introduction and repeated transmission.