About

Marc Verhougstraete is an Associate Professor in the Department of Environmental Health Sciences at the University of Arizona's Zuckerman College of Public Health. His primary research focuses on environmental microbiology and water quality, with an emphasis on understanding the sources, occurrence, and transport of waterborne pathogens through the use of fecal indicator organisms and molecular source tracking. His work aims to integrate microbial water quality data with hydrological catchment dynamics and landscape patterns, employing Quantitative Microbial Risk Assessment to enhance environmental management practices that protect both human and ecosystem health. Recent research efforts include investigating the effects of healthcare intervention practices to reduce the transmission of pathogenic agents and associated healthcare infections. His overarching goal is to prevent human exposure to pathogenic organisms by increasing scientific understanding of complex environments through a multifaceted toolbox approach.

Research topics

• Medicine
• Computer Science
• Political Science
• Psychology
• Biology
• Engineering
• Environmental health
• Microbiology
• Biotechnology
• Waste management
• Psychiatry
• Surgery
• Dentistry

Selected publications

• Fomite workshop recommendations addressing the role of surfaces in virus transmission in the built environment

  mSphere · 2025-08-20

  reviewOpen access

  The emergence of SARS-CoV-2 has led to a need to assess the role of fomites in viral transmission within the built environment. Assessing the role of fomites is necessary for developing intervention strategies for controlling emerging pathogens. A fomite workshop with experts was convened in November 2024 by academia, several government agencies, and public health officials to evaluate existing data and discuss how to mitigate risks. Fomite transmission is influenced by the nature of the built environment, population density and proximity, environmental factors (humidity, heat, etc.), virus survival, surface type, engineering controls (ventilation, physical barriers, etc.), and human behaviors. Based on our current data, direct contact with a contaminated surface/fomite, even for respiratory viruses, presents a risk of viral exposure and transmission by both contact with the fomite and resuspension in the air. Even respiratory viruses can be resuspended from fomites following human and pet movement, activities (e.g., vacuuming, toilet flushing, etc.), or changes in ventilation/indoor airflow. After resuspension from surfaces, microbes can be potentially inhaled (contributing to droplet and/or aerosol exposure) and/or re-deposited from primary to secondary fomites. Development of standard methods (molecular, chemical/physical, and infectivity assays) for detecting the presence of viruses on fomites and human behavior modeling would help to determine the most effective infection prevention strategies.

  PublisherDOI

• A risk-risk tradeoff approach for incorporating the public’s risk perceptions into quantitative microbial risk assessment

  Journal of Occupational and Environmental Hygiene · 2025-01-02 · 3 citations

  articleOpen access

  In public health, risk experts often define acceptable risk targets without community input. We developed a novel method for applying behavioral microeconomics to integrate individuals' risk preferences into risk assessment. To demonstrate this methodology, we explored a risk-risk tradeoff case scenario: increased asthma risk from increased cleaning and disinfection (C&D) and increased infection risk from decreased C&D for healthcare staff. Utilizing a risk-risk tradeoff (RRTO) framework, two datasets were informed with RRTO survey data describing the risks individuals would accept for one outcome to offset risk in another (i.e., "risk target"). A quantitative microbial risk assessment (QMRA) was deployed to output "critical concentrations," viral concentrations on surfaces that yield risk targets for a single contaminated surface touch and a work shift. Critical concentrations were over four orders of magnitude larger for single-touch scenarios. Critical concentrations across risk target datasets were similar. Using the RRTO framework to inform QMRA advances the incorporation of individuals' risk preferences in risk analyses outside economics.

  PublisherOA PDFDOI

• Impact of terminal cleaning in rooms previously occupied by patients with healthcare-associated infections

  PLoS ONE · 2024-07-10 · 7 citations

  articleOpen access1st authorCorresponding

  Healthcare associated infections (HAIs) are costly but preventable. A limited understanding of the effects of environmental cleaning on the riskiest HAI associated pathogens is a current challenge in HAI prevention. This project aimed to quantify the effects of terminal hospital cleaning practices on HAI pathogens via environmental sampling in three hospitals located throughout the United States. Surfaces were swabbed from 36 occupied patient rooms with a laboratory-confirmed, hospital- or community-acquired infection of at least one of the four pathogens of interest (i.e., Acinetobacter baumannii (A. baumannii), methicillin resistant Staphylococcus aureus (MRSA), vancomycin resistant Enterococcus faecalis/faecium (VRE), and Clostridioides difficile (C. difficile)). Six nonporous, high touch surfaces (i.e., chair handrail, bed handrail, nurse call button, desk surface, bathroom counter near the sink, and a grab bar near the toilet) were sampled in each room for Adenosine Triphosphate (ATP) and the four pathogens of interest before and after terminal cleaning. The four pathogens of interest were detected on surfaces before and after terminal cleaning, but their levels were generally reduced. Overall, C. difficile was confirmed on the desk (n = 2), while MRSA (n = 24) and VRE (n = 25) were confirmed on all surface types before terminal cleaning. After cleaning, only MRSA (n = 6) on bed handrail, chair handrail, and nurse call button and VRE (n = 5) on bathroom sink, bed handrail, nurse call button, toilet grab bar, and C. difficile (n = 1) were confirmed. At 2 of the 3 hospitals, pathogens were generally reduced by >99% during terminal cleaning. One hospital showed that VRE increased after terminal cleaning, MRSA was reduced by 73% on the nurse call button, and VRE was reduced by only 50% on the bathroom sink. ATP detections did not correlate with any pathogen concentration. This study highlights the importance of terminal cleaning and indicates room for improvement in cleaning practices to reduce surface contamination throughout hospital rooms.

  PublisherOA PDFDOI

• A microbial risk assessor's guide to Valley Fever (Coccidioides spp.): Case study and review of risk factors

  The Science of The Total Environment · 2024-01-18 · 2 citations

  reviewOpen access
  PublisherOA PDFDOI

• Research gaps and priorities for quantitative microbial risk assessment (QMRA)

  Risk Analysis · 2024-05-21 · 31 citations

  articleOpen access

  The coronavirus disease 2019 pandemic highlighted the need for more rapid and routine application of modeling approaches such as quantitative microbial risk assessment (QMRA) for protecting public health. QMRA is a transdisciplinary science dedicated to understanding, predicting, and mitigating infectious disease risks. To better equip QMRA researchers to inform policy and public health management, an Advances in Research for QMRA workshop was held to synthesize a path forward for QMRA research. We summarize insights from 41 QMRA researchers and experts to clarify the role of QMRA in risk analysis by (1) identifying key research needs, (2) highlighting emerging applications of QMRA; and (3) describing data needs and key scientific efforts to improve the science of QMRA. Key identified research priorities included using molecular tools in QMRA, advancing dose-response methodology, addressing needed exposure assessments, harmonizing environmental monitoring for QMRA, unifying a divide between disease transmission and QMRA models, calibrating and/or validating QMRA models, modeling co-exposures and mixtures, and standardizing practices for incorporating variability and uncertainty throughout the source-to-outcome continuum. Cross-cutting needs identified were to: develop a community of research and practice, integrate QMRA with other scientific approaches, increase QMRA translation and impacts, build communication strategies, and encourage sustainable funding mechanisms. Ultimately, a vision for advancing the science of QMRA is outlined for informing national to global health assessments, controls, and policies.

  PublisherOA PDFDOI

• Formerly used defense sites on Unalaska Island, Alaska: Mapping a legacy of environmental pollution

  Integrated Environmental Assessment and Management · 2024-02-14 · 7 citations

  articleOpen accessSenior author

  Abstract Unalaska Island, Alaska, served as a US military base during World War II. The military installed bases on Unalaska and nearby islands, many of which were built adjacent to Unangan communities. The military used toxic compounds in its operations and left a legacy of pollution that may pose health risks to residents and local wildlife. The goals of this study were to identify hotspots of contamination remaining at Unalaska formerly used defense (FUD) sites, evaluate the risk posed by arsenic, and examine “no US Department of Defense action indicated” (NDAI) status determinations for FUD sites near communities. We compiled soil chemistry data from remediation reports prepared by the US Army Corps of Engineers at 18 FUD sites on and near Unalaska. Nine had past and/or active remediation projects and on-site sampling data. Eight sites did not have sampling data and were characterized as NDAI. One site was listed as closed. For the nine sites with sampling data, we compiled data for 22 contaminants of concern (COC) and compared concentrations to soil cleanup levels for human health (18 AAC 75.341). We mapped contaminant concentrations exceeding these levels to identify hotspots of contamination. We found that concentrations of some of the 22 COC exceeded Alaska cleanup levels despite remediation efforts, including diesel range organics, arsenic, and lead. The highest COC concentrations were at the FUD site adjacent to the City of Unalaska. A quantitative risk assessment for arsenic found that the risk of exposure through drinking water is low. We highlight concerns with NDAI designations and current remedial practices at remote FUD sites located adjacent to communities. Our data suggest the need for further remediation and monitoring efforts on Unalaska for certain contaminants and research to examine potential threats to human and animal health associated with these sites. Integr Environ Assess Manag 2024;20:1420–1431. © 2024 SETAC Key Points We found that concentrations of some of the 22 contaminants of concern (COC) exceeded Alaska cleanup levels despite remediation efforts, including diesel range organics, arsenic, and lead, and that the highest COC concentrations were present at the formerly used defense (FUD) site adjacent to the City of Unalaska. We conducted a quantitative risk assessment for arsenic and found that the risk of exposure through drinking water is low. We highlight concerns with NDAI designations and current remedial practices at remote FUD sites located adjacent to communities. Our data suggest the need for further remediation and monitoring efforts on Unalaska for certain contaminants and research to examine potential threats to human and animal health associated with these sites.

  PublisherOA PDFDOI

• Developing a Risk Calculator Tool to Reduce Respiratory Viral Transmission in Classrooms

  2024-04-30 · 1 citations

  article
  PublisherDOI

• Effects of recirculation and air change per hour on COVID-19 transmission in indoor settings: A CFD study with varying HVAC parameters

  Heliyon · 2024-07-23 · 13 citations

  articleOpen access

  COVID-19 has already claimed over 7 million lives and has infected over 775 million people globally [1]. SARS-CoV-2, the virus that causes Covid-19, spreads primarily through droplets from infected people's airways, rendering Heating, Ventilation, and Air Conditioning (HVAC) systems critical in controlling infection risk levels in the indoor environment. To understand the dynamics of exhaled droplets and aerosols and the percentage of particles that are inhaled, escaped, recirculated, or trapped on different surfaces for a variety of environmental settings, we have presented our findings from the Computational Fluid Dynamics (CFD) modeling to investigate the impact of changing HVAC parameters in this paper. When combined with the spatial and temporal distribution of droplets, this method can be used to assess the potential risk and strengthen resilience. This finding demonstrates the viability and usefulness of CFD for modeling the distribution and dynamics of droplets and aerosols in confined environments. Our study demonstrates that raising the Air Change per Hour (ACH) from 2 to 8 reduces the risk of particle inhalation by nearly 70 %. Additionally, limiting the amount of air recirculation or increasing the amount of fresh air helps to reduce the number of airborne particles in an indoor space. To reduce the potential for respiratory droplet-related transmission and to provide relevant recommendations to the appropriate authority, the same computational approach could be applied to a wide range of ventilated indoor environments such as public buses, restaurants, exhibitions, and theaters.

  PublisherOA PDFDOI

• Research gaps and priorities for quantitative microbial risk assessment (QMRA)

  UNC Libraries · 2024-11-20 · 2 citations

  articleOpen access

  The coronavirus disease 2019 pandemic highlighted the need for more rapid and routine application of modeling approaches such as quantitative microbial risk assessment (QMRA) for protecting public health. QMRA is a transdisciplinary science dedicated to understanding, predicting, and mitigating infectious disease risks. To better equip QMRA researchers to inform policy and public health management, an Advances in Research for QMRA workshop was held to synthesize a path forward for QMRA research. We summarize insights from 41 QMRA researchers and experts to clarify the role of QMRA in risk analysis by (1) identifying key research needs, (2) highlighting emerging applications of QMRA; and (3) describing data needs and key scientific efforts to improve the science of QMRA. Key identified research priorities included using molecular tools in QMRA, advancing dose-response methodology, addressing needed exposure assessments, harmonizing environmental monitoring for QMRA, unifying a divide between disease transmission and QMRA models, calibrating and/or validating QMRA models, modeling co-exposures and mixtures, and standardizing practices for incorporating variability and uncertainty throughout the source-to-outcome continuum. Cross-cutting needs identified were to: develop a community of research and practice, integrate QMRA with other scientific approaches, increase QMRA translation and impacts, build communication strategies, and encourage sustainable funding mechanisms. Ultimately, a vision for advancing the science of QMRA is outlined for informing national to global health assessments, controls, and policies.

  PublisherDOI

• Hierarchical agent-based MRSA transmission simulation model of university classrooms for risk assessment: mobility, contact, and cleaning

  International Journal of Risk Assessment and Management · 2023-01-01

  articleSenior author

  Methicillin-resistant Staphylococcus aureus (MRSA) is a bacterium capable of triggering infections that range from minor to life-threatening. Surface hygiene is crucial to prevent MRSA transmission, especially in public places such as schools and university campuses where large numbers of people congregate and routinely contact shared surfaces. The current study developed hierarchical agent-based models that simulated human-behaviour-based characteristics, MRSA transmission dynamics, and student interactions in the university classroom settings. The micro-scale model focused on individual touch behaviours and other environmental factors influencing the transfer rate. The macro-scale level included cleaning and class schedules scenarios to inform policy. The models allow for the manipulation of critical components of MRSA transmission at the individual and classroom level. Results demonstrate the importance of hand sanitiser and twice weekly surface cleanings to control transmission rates. This study advances facilities and health management capacities by highlighting robust quantitative relationships among micro-activities, contamination levels, and infection risks.

  PublisherDOI

Frequent coauthors

• Amanda M. Wilson

  University of Arizona

  17 shared

• Joan B. Rose

  Michigan State University

  15 shared

• Kelly A. Reynolds

  14 shared

• Emily Cooksey

  University of Arizona

  7 shared

• Kerry A. Hamilton

  7 shared

• Jennifer Pearce‐Walker

  University of Arizona

  7 shared

• Robert A. Canales

  George Washington University

  5 shared

• Charles P. Gerba

  5 shared