Health and Human Services

How GIS Brings Wastewater Surveillance to Life

What do you think happens to the water flushed down your toilets and sinks? Did you ever consider that your communities’ wastewater might provide insight into its overall health? In some cases, communities across the nation are using geographic information systems (GIS) to support wastewater surveillance systems to monitor local wastewater for the occurrence of diseases and health threats like polio, hepatitis, opioid use, antibiotic resistance, and recently, COVID-19. According to the CDC, there are more than 700 wastewater sampling sites in the US currently testing for viral shedding for the SARS-CoV-2 virus that causes COVID-19. Those sites are distributed across nearly 75% of the nation’s states and territories, monitoring the waste of approximately 30% of the U.S. population.

Communities with wastewater surveillance programs enjoy a number of benefits. A single sample could represent hundreds, thousands, or even millions of people in an area, making it a very efficient and cost-effective surveillance method. The testing process is quick too, giving public health officials more lead time for making decisions, allocating resources to where they are needed most, and communicating any potential health concerns with stakeholders. Not only is this process convenient and non-intrusive but it is also equitable and inclusive, as everyone served by the sewershed is surveyed. Wastewater surveillance also provides anonymity as community wastewater is tested in aggregate with results representing the entire area rather than specific individuals.

Many organizations are turning to GIS to improve wastewater surveillance programs by:

Site Selection: Determining Where to Surveil

It may be safe to assume that site selection for a wastewater surveillance system should be based on an area that is already experiencing high occurrences of the health threat of interest (e.g., COVID-19, antibiotic resistance, substance misuse). However, this simplistic view comes with a risk of “attentional bias” in which important information may be ignored if the focus is too obvious or narrow. With GIS, health departments can consider multiple contextual and risk factors that help them take a more holistic approach. Not only does this improve the decision-making about surveillance site selection but opens the door to applying predictive spatial analytics to determine where an outbreak or threat may occur in the future.

GIS makes it simple to understand where large populations reside, which communities are at a greater risk for severe illness, and places where clinical or public health resources may be unavailable or underused. Location-intelligence allows you to map social vulnerability, age, and other factors that help identify at-risk groups and target locations for testing sites that serve the greatest need.

For example, GIS would help in selecting the best sites for COVID-19 wastewater testing as location intelligence would locate where in a community there has been low vaccination rates, high hospitalization rates, low testing rates, and a high prevalence of service workers. These factors can all contribute to high COVID-19 rates. So, testing wastewater in these areas before an outbreak occurs allows governments and organizations to be proactive.

For example, UC San Diego was able to detect COVID-19 in their wastewater before individuals started showing symptoms. The university tied their wastewater testing results to a live map they created with GIS, which showed, in real-time, which buildings on their campus presented a positive COVID-19 reading. The campus was then able to quickly communicate these results and encourage testing among those at risk (people living or working in the affected building). The use of GIS allowed the university to curb the spread of COVID-19 on their campus, preventing potential closures.

Access to Care: Prioritizing Vulnerable Populations

Access to health care and services can be impacted by barriers such as social, racial, economic, and physical factors. Because these factors vary across places, some communities have more difficulty accessing services than others. In some cases, a geographically targeted wastewater surveillance system can ensure that those communities do not fall through the cracks. Esri’s Living Atlas of the World provides a layer of data known as the CDC’s Social Vulnerability Index (SVI). The Social Vulnerability Index uses U.S. Census data to identify and map communities that will most likely need support before, during and after emergency events like disease outbreaks. The Social Vulnerability Index ranks communities across 15 social factors and four thematic areas including socioeconomic status, household composition and disability, minority status and language, and housing type and transportation. All factors contribute to a community’s cumulative vulnerability to adverse health impacts.

By mapping the SVI data it becomes easier to prioritize vulnerable communities when selecting wastewater surveillance sites.

Proactive Response with Real-Time Data

In times of crisis, real-time data is essential for decision making, resource allocation, and communication between departments. GIS can visually display data in an easy-to-read format, which can then be used to create targeted solutions. For example, in 2017 the City of Tempe, Arizona experienced a 20% increase in opioid related overdose deaths and began using a wastewater surveillance system to monitor and test areas in the city for the presence of opioids and other substances. The city was able to monitor their wastewater treatment plant and see the prevalence of drugs in an area, an estimated number of users, and even an estimated number of overdoses.

All this information was then fed into a public ArcGIS Dashboard, a visual display that presents data in an easy to read format, and shared with the public, city leaders and city departments like the Fire Medical Rescue department. Not only was GIS used to help raise awareness on the opioid epidemic, but it allowed city leaders to respond to this health crisis almost immediately and with location-driven solutions. It also provided real-time communication to warn the public and emergency responders of possible deadly strains of synthetic fentanyl found in the community wastewater.

With long time experience in wastewater surveillance for opioids, Tempe was able to pivot quickly when COVID-19 arose, creating new surveillance dashboards reflecting overall viral shedding as well as various equity metrics.

Wastewater surveillance is also employed at the state level. The state of Missouri has been tracking COVID-19 in about 100 sewersheds representing nearly half of their population. They’re sharing geographic and temporal trends as well as the variants of interest as they wax and wane across the state.

Wastewater Surveillance: An Essential Tool for Public Health

The use of GIS for wastewater surveillance programs enhances site selection, ensures equitable approaches to vulnerable communities that may not have access to care or testing and facilitates timely responses to health crises. Wastewater testing can provide situational awareness about what is happening in a community and promote smarter response by clarifying where, what kind, and how much support is needed.

Connect with our team  if you’d like to learn more about how GIS can support your wastewater surveillance efforts.

About the author

Dr. Este Geraghty, MD, MS, MPH, CPH, GISP, is the Chief Medical Officer at Esri where she leads strategy and messaging for the Health and Human Services sector. Dr. Geraghty has been with Esri since 2014 and has led business development and solution development in the market. During her time at Esri, Dr. Geraghty has helped organizations around the world use location intelligence to combat Zika virus, finish the fight against polio, grapple with the opioid crisis, combat homelessness, enhance health preparedness and response, inform strategic planning, optimize healthcare access, and traverse the COVID-19 pandemic while tackling inequity. Formerly the Deputy Director of the Center for Health Statistics and Informatics with the California Department of Public Health, Dr. Geraghty led the state vital records and public health informatics programs. There she engaged in statewide initiatives in meaningful use, health information exchange, open data and interoperability. While serving as an Associate Professor of Clinical Internal Medicine at the University of California at Davis she conducted research on geographic approaches to influencing health policy and advancing community development programs. In addition to her degrees in Medicine, Medical Informatics and Public Health, Dr. Geraghty is also a board-certified public health professional (CPH) and a Geographic Information Systems Professional (GISP).


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