About

Kacey Ernst is a Professor and Program Director in the Department of Epidemiology at the Mel and Enid Zuckerman College of Public Health. Her research focuses on the epidemiology of infectious diseases. She is involved in academic and community efforts to understand and address infectious disease transmission and prevention.

Research topics

• Medicine
• Virology
• Internal medicine
• Ecology
• Biology
• Family medicine
• Zoology
• Immunology
• Sociology
• Nursing
• Environmental health
• Geography
• Agroforestry
• Environmental science
• Gerontology
• Statistics
• Pathology
• Psychiatry
• Pediatrics
• Genetics

Selected publications

• Behavioral patterns in latrine use and handwashing in rural western Kenya: Age, time of day, and the role of perceived safety

  PLoS ONE · 2026-03-27

  articleOpen accessSenior author

  Latrine use enhances health benefits, safety, dignity, and social status. Despite increased latrine coverage, some children and adults do not consistently use latrines. The present study aimed to describe latrine use and handwashing after urination and defecation by age and time of day, and to explore factors associated with latrine use at each time of day. A cross-sectional, population-based survey was conducted from July 17 to September 21, 2023 in western Kenya, targeting individuals aged 4 years or older (n = 528 analyzed). Overall, latrine use tended to be more frequent among adults than children, for defecation than urination, and during the daytime and early morning compared with at night. Handwashing practices after urination and defecation showed similar patterns. For urination, compared with young adults (18-39 years), young children (4-10 years) were less likely to use latrines across all times of day, with reductions of approximately 60-85%. For defecation, compared with adults (18 + years), young children were even less likely to use latrines across all times of day (approximately 90-95% lower likelihood). Similarly, adolescents (11-17 years) had approximately 75% lower latrine use for defecation at night and early in the morning compared with adults. In contrast, individuals who felt safe walking to the latrine at night were substantially more likely to use latrines for both urination and defecation than those who perceived the walk as neither safe nor unsafe or unsafe. Therefore, simple, low-cost interventions, such as promoting the use of flashlights, constructing latrines closer to households, and better connecting sanitation knowledge to daily practices, are crucial for improving sanitation behaviors.

  PublisherDOI

• Concordance between self-reported SARS-CoV-2 positivity and laboratory-confirmed positivity

  PLoS ONE · 2025-10-17

  articleOpen accessCorresponding

  As the use and availability of at-home antigen tests for SARS-CoV-2 infection have increased, the number of individuals with SARS-CoV-2 infections that are reported to state COVID-19 surveillance systems have decreased. Self-reported infection dates are critical to accurately track incidence and outbreaks of COVID-19 and for continued research on illness progression; however, the reliability of self-reported infection dates is unknown to date. To assess accuracy of self-reported test dates, we utilized self-reported SARS-CoV-2 testing data from the Arizona CoVHORT Study (CoVHORT) and laboratory-confirmed testing data collected by the Arizona Department of Health Services (ADHS) and calculated the difference in days between dates to examine their percent agreement. We used logistic regression to assess if any participant characteristics were associated with self-reporting a test date >7 days different than the laboratory confirmed date. A total of 1,900 CoVHORT participants aged 18 years or older were included in our analyses. Most participants (82.5%) reported a test date within 7 days of the laboratory confirmed date of their illness. Increasing age and number of weeks between testing positive and self-reporting the test date were both significantly associated with a difference of 7 days or greater between dates. There was an 84% increase (OR=1.84, 95% CI = 1.11-3.06) in likelihood of inaccurately self-reporting their SARS-CoV-2 test date for participants aged 55 years and older and a 2% increase (OR=1.02, 95% CI = 1.02-1.03) for each elapsed week following their SARS-CoV-2 test. We observed an 82% percent agreement (dates within 7 days of each other) between self-reported and laboratory confirmed test dates, suggesting that self-reported SARS-CoV-2 test dates are sufficient for identifying and tracking Long COVID or Post-COVID Conditions when a laboratory-confirmed test date is not available. However, increasing age and greater time between test date and date of self-report were found to decrease the agreement between self-reported and laboratory confirmed test dates.

  PublisherDOI

• Structural features of outdoor latrines influence the abundance of Anopheles gambiae s.l. and Culex quinquefasciatus in a village in Kisumu County, western Kenya

  Parasites & Vectors · 2025-08-27 · 1 citations

  articleOpen accessSenior author

  BACKGROUND: Malaria remains a leading cause of mortality in Kenya, despite concerted efforts in malaria vector control. Reducing outdoor transmission is a key factor in addressing residual malaria. Outdoor latrines are characterized as semi-sheltered structures with humid environments, which may provide an ideal resting site for Anopheles species to feed on human blood and subsequently rest. This study aimed to quantify the abundance of adult mosquitoes in houses and outdoor latrines, as well as explore the environmental factors associated with mosquito abundance. METHODS: Monthly mosquito sampling was conducted in 50 houses and their corresponding outdoor latrines using Prokopack aspirators from July 2023 to April 2024. Household interviews were conducted concurrently to collect data on the number of individuals sleeping in the houses and the quantity of bednets used within the households. In addition, blood meal sources were identified through polymerase chain reaction (PCR) analysis of blood-fed mosquitoes collected from December 2023 to April 2024. RESULTS: Among anopheline species, the An. funestus group was the most common, followed by An. gambiae s.l. in both houses and latrines. In anophelines, the human blood index was 50.0% (n = 15) in houses and 33.3% (n = 4) in latrines, while bovine blood was 60.0% (n = 18) and 66.7% (n = 8), respectively. Ventilated improved pit (VIP) latrines were associated with a 61% decrease in An. gambiae s.l. abundance (adjusted incidence rate ratio [aIRR] = 0.39, 95% confidence interval [CI] = 0.16-0.96) and a 62% decrease in Culex quinquefasciatus abundance (aIRR = 0.38, 95% CI = 0.24-0.60), compared with pit latrines. The presence of a bathing space in latrines was associated with a 23% increase in Cx. quinquefasciatus abundance (aIRR = 1.88, 95% CI = 1.23-2.89) compared with latrines without a bathing space. There was an inverse association between the number of individuals using the latrines and Cx. quinquefasciatus abundance (aIRR = 0.93, 95% CI = 0.89-0.97). CONCLUSIONS: VIP latrines were associated with a lower abundance of An. gambiae s.l. and Cx. quinquefasciatus compared with pit latrines, whereas the presence of a bathing space in latrines was associated with a higher abundance of Cx. quinquefasciatus compared with latrines without bathing spaces. Integrative public health programs that promote the construction of VIP latrines as a low-cost intervention may provide co-benefits for both sanitation and vector control.

  PublisherOA PDFDOI

• An analytical evaluation of contact tracing systems using real-world individual-level data

  International Journal of Medical Informatics · 2025-06-19

  article
  PublisherDOI

• Data Parameters From Participatory Surveillance Systems in Human, Animal, and Environmental Health From Around the Globe: Descriptive Analysis

  JMIR Public Health and Surveillance · 2025-03-26 · 8 citations

  articleOpen access

  BACKGROUND: Emerging pathogens and zoonotic spillover highlight the need for One Health surveillance to detect outbreaks as early as possible. Participatory surveillance empowers communities to collect data at the source on the health of animals, people, and the environment. Technological advances increase the use and scope of these systems. This initiative sought to collate information from active participatory surveillance systems to better understand parameters collected across the One Health spectrum. OBJECTIVE: This study aims to develop a compendium of One Health data parameters by examining participatory surveillance systems active in 2023. The expected outcomes of the compendium were to pinpoint specific parameters related to human, animal, and environmental health collected globally by participatory surveillance systems and to detail how each parameter is collected. The compendium was designed to help understand which parameters are currently collected and serve as a reference for future systems and for data standardization initiatives. METHODS: Contacts associated with the 60 systems identified through the One Health Participatory Surveillance System Map were invited by email to provide specific data parameters, methodologies used for data collection, and parameter-specific considerations. Information was received from 38 (63%) active systems. Data were compiled into a searchable spreadsheet-based compendium organized into 5 sections: general, livestock, wildlife, environmental, and human parameters. An advisory group comprising experts in One Health participatory surveillance reviewed the collected parameters, refined the compendium structure, and contributed to the descriptive analysis. RESULTS: A comprehensive compendium of data parameters from a diverse array of single-sector and multisector participatory surveillance systems was collated and reviewed. The compendium includes parameters from 38 systems used in Africa (n=3, 8%), Asia (n=9, 24%), Europe (n=12, 32%), Australia (n=3, 8%), and the Americas (n=12, 32%). Almost one-third of the systems (n=11, 29%) collect data across multiple sectors. Many (n=17, 45%) focus solely on human health. Variations in data collection techniques were observed for commonly used parameters, such as demographics and clinical signs or symptoms. Most human health systems collected parameters from a cohort of users tracking their own health over time, whereas many wildlife and environmental systems incorporated event-based parameters. CONCLUSIONS: Several participatory surveillance systems have already adopted a One Health approach, enhancing traditional surveillance by identifying shared health threats among animals, people, and the environment. The compendium reveals substantial variation in how parameters are collected, underscoring the need for further work in system interoperability and data standards to allow for timely data sharing across systems during outbreaks. Parameters collated from across the One Health spectrum represent a valuable resource for informing the development of future systems and identifying opportunities to expand existing systems for multisector surveillance.

  PublisherOA PDFDOI

• Evaluating Associations Between Drought and West Nile Virus Epidemics: A Systematic Review

  Microorganisms · 2025-12-15

  articleOpen access

  Human West Nile virus (WNV) infections can have severe neurological health effects, especially among those over 50 years of age. As changes in weather patterns lead to more frequent and intense droughts, there is a public health need for improved understanding of drought associated WNV risks. While multiple studies have reported an association between drought conditions and human WNV cases, this information has not yet been synthesized systematically across studies. Our review aims to evaluate the existing evidence of an association between drought and human WNV cases while considering the impacts of different study regions, methodological approaches, drought metrics, and WNV case definitions. We conducted a systematic literature search of peer-reviewed epidemiological studies that examined a potential association between drought and human WNV cases. Our inclusion criteria targeted studies that employed measures of drought beyond precipitation and reported effect estimates along with measures of error. The literature search and screening process resulted in the inclusion of nine papers with study periods spanning from 1999 to 2018. The included peer-reviewed publications employed a wide variety of study designs and methods, such as linear mixed-effects models, generalized linear models using simultaneous autoregression, generalized additive models, Bayesian model averaging, and a case-crossover design using conditional logistic regression models. We summarize the key findings and provide study quality evaluations for each of the nine included studies. Studies that analyzed drought indices averaged over a seasonal period of three to four months reported positive associations between drought and WNV. However, studies that analyzed drought indicator variables averaged over weekly periods of time had less consistent results. We discuss potential mechanisms underlying the observed associations between drought and human WNV cases.

  PublisherOA PDFDOI

• Developing and validating a HEalthCare NAvigation Competency (HECNAC) Scale for refugees in the United States

  PLoS ONE · 2025-01-30 · 2 citations

  articleOpen accessCorresponding

  The complex healthcare system in the United States (US) poses significant challenges for people, particularly minorities such as refugees. Refugees often encounter additional layers of challenges to healthcare navigation due to unfamiliarity with the system, limited health literacy, and language barriers. Despite their challenges, it is difficult to identify the gaps as few tools exist to measure navigation competency among this population and many conventional tools assume English proficiency, making them inadequate for refugees and other immigrants. To address this gap, this study developed and validated a HEalthCare NAvigation Competency (HECNAC) Scale tailored to refugees' needs. The scale development process followed three phases: domain identification through a literature review and stakeholder interviews (n = 15), content validation through the Delphi method (2 rounds, n = 12), and face validity assessment via cognitive interviews (2 rounds, n = 4). Based on a literature review and stakeholder interviews, the initial version of the scale was developed, including ten domains and 47 items. An introductory email concerning the scale and the Delphi process was subsequently sent to 21 eligible experts, including staff from refugee resettlement agencies, health care providers serving refugee communities, and refugees. Twelve experts completed the two rounds of the Delphi, resulting in a consensus on 39 items. After conducting cognitive interviews with 4 Afghan refugees, the scale was finalized with ten domains and 35 items. The finalized scale captures multifaceted aspects of healthcare navigation crucial for refugees, organized into domains such as health system knowledge, insurance, making an appointment, transportation, preparing for a visit, in the clinic, interpretation, medicine, medical bills, and preventive care. Overall, the HECNAC Scale represents a significant step towards understanding and assessing refugees' competencies in navigating the US healthcare system. It has the potential to guide tailored interventions and standardized training curricula and ultimately mitigate persistent barriers faced by refugees in accessing healthcare services.

  PublisherDOI

• Long COVID and the Increased Risk of Food Insecurity Among Participants in Arizona CoVHORT: A matched cohort study

  medRxiv · 2025-11-17

  preprintOpen accessSenior author

  Abstract Objectives To assess whether individuals with long COVID face a higher risk of food insecurity compared with those without long COVID. Methods We used data from the Arizona CoVHORT, which is a prospective longitudinal study of SARS-CoV-2 health outcomes initiated in May 2020. Participants with confirmed infections who completed a symptom survey ≥6 months post-infection were eligible (n = 2415). We matched participants with long COVID to participants who did not have long COVID by gender, age group, income bracket, and date of first assessment of food insecurity (±6 months). We estimated the association between long COVID and food insecurity using a conditional logistic regression analysis. Results Participants with long COVID had significantly greater odds of food insecurity (adjusted odds ratio = 1.47; 95% confidence interval = 1.06 - 2.04). Conclusions Long COVID significantly increases vulnerability to food insecurity. This highlights the need for integrated health and social interventions for individuals with long COVID. WHAT IS ALREADY KNOWN ON THIS TOPIC Food Insecurity has been shown to be an important risk factor for long COVID, but we do not know whether long COVID independently increases the risk of food insecurity, nor have studies adopted a cohort design approach to examine the relationship between long COVID and food insecurity. This study is the first to analyze the association between long COVID and food Insecurity using a matched cohort data within the United States. WHAT THIS STUDY ADDS This study uniquely adds to the current knowledge base by providing evidence that long COVID is independently associated with a significantly increased risk of food insecurity among adults in Arizona, after adjusting for confounders. We found that adults with long COVID in the Arizona CoVHORT had 47% higher odds of experiencing food insecurity compared to matched controls without long COVID. This study provides robust statistical support for a direct association between long COVID and food insecurity and advances the field by evidencing a previously under-explored dimension of the pandemic’s long-term impact, thus, highlighting an urgent need for integrated screening and intervention strategies at the intersection of chronic illness and nutrition insecurity. HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE OR POLICY Our study provides evidence that long COVID not only affects health of individuals but also social and economic well-being, including food access and stability. Healthcare and public health systems should integrate routine screening for food insecurity in outpatient care, primary care, and long COVID clinics. Early detection and referral to nutritional or financial assistance programs may reduce the combined effects of chronic illness and economic strain. These interventions are critical for groups disproportionately impacted by the pandemic’s longer-term effects, including low-income households, women, and communities of color. Expanding safety net programs and tracking social consequences of infectious diseases are vital for public health preparedness.

  PublisherOA PDFDOI

• Impacts of ground-based ULV pyrethroid sprays on abundance and age structure of the Zika vector, <i>Aedes aegypti</i> (Diptera: Culicidae), in urban Arizona

  Journal of Medical Entomology · 2025-04-03

  article

  Aedes aegypti (L.), the primary mosquito vector of arboviruses such as dengue and Zika, has a global distribution that includes the southern United States. Control of this peridomestic mosquito is challenging. Ultra-low volume (ULV) pyrethroid sprays are commonly used against adult mosquitoes to break transmission during a disease outbreak, although efficacy data are limited. This study examined the impacts of ULV sprays on Ae. aegypti vectorial capacity as measured by vector abundance and age structure in two cities in Maricopa County, AZ with robust Ae. aegypti populations and a well-developed vector management program. We assessed impacts of routine ULV applications conducted by Maricopa Vector Control Division during the summer rainy seasons of 2017 to 2019 to determine whether existing practices mainly targeting Culex spp. also suppressed Ae. aegypti. The insecticide formulations applied for Culex spp. control (Duet and Permanone 30-30) did not affect Ae. aegypti abundance, but Duet applications slightly reduced female mosquito age. Deltagard, the insecticide product used specifically against Ae. aegypti, was only applied three times in 2018 over small areas, so efficacy assessment was difficult. Deltagard was associated with a small decline in Ae. aegypti abundance. CDC bottle bioassays of Ae. aegypti collected in the study area showed resistance to permethrin and deltamethrin. Overall, the lack of significant mosquito population suppression or age structure changes after insecticide applications suggest that current tools used by Maricopa Vector Control Division are unlikely to effectively control Ae. aegypti populations in the event of a disease outbreak.

  PublisherDOI

• Developing and validating modular surveys for vector-borne diseases: A study protocol

  PLoS ONE · 2025-08-25

  articleOpen access

  Vector-borne diseases are an increasing threat to human health and well-being in the United States. Understanding public perception and practices to reduce vector abundance and vector-human contact can guide effective interventions. Nevertheless, vector-borne disease surveys, which are widely used in the field to understand public perception and practices, are often inconsistent in terms of structure and implementation. This protocol is designed to provide guidance for public health professionals and researchers in the development of future knowledge, attitudes, and practices studies by ensuring uniformity in design and structure. This manuscript describes a rigorous three-phase protocol for the development of standardized vector-borne disease survey modules that can be used throughout the United States to generate data that are comparable across diverse regions. During phase one, a workshop with subject matter experts and a comprehensive literature review will be conducted to identify survey domains and generate items of interest. Survey items will also be mapped based on two theoretical frameworks: the Health Belief Model and the Risks, Attitudes, Norms, Abilities, and Self-Regulation framework. Standards across knowledge, attitudes, and practices surveys will enhance the analysis and interpretation of the data across geographies and time. During phase two, a group of expert judges will evaluate survey items based on content relevance, representativeness, and technical quality. During the final phase, cognitive interviews and surveys with target audience groups will be conducted to measure and ensure the face validity, reliability, and external validity of the modules. Participants will be drawn from a diverse range of educational backgrounds and geographic locations. The surveys developed through this protocol will facilitate acquisition of insights into the public's knowledge, attitudes, and practices concerning vector-borne diseases, allowing for the collection of comparable data across various regions in the United States.

  PublisherDOI

Recent grants

• NIH Grant R15AI10011801

  NIH · $376k · 2016

• On the Edge: Dengue and Climate

  NIH · $2.2M · 2012–2017

Frequent coauthors

• Andrew J. Monaghan

  University of Colorado Boulder

  48 shared

• Mary H. Hayden

  University of Colorado Colorado Springs

  43 shared

• Steven Haenchen

  University of Southern California

  40 shared

• Kathleen Walker

  University of Arizona

  36 shared

• Mary H. Hayden

  University of Colorado Colorado Springs

  36 shared

• Katherine L. Dickinson

  35 shared

• Elizabeth T. Jacobs

  University of Arizona

  34 shared

• Kristen Pogreba-Brown

  26 shared

Labs

• Ernst LabPI