During the COVID-19 pandemic, scientists employed every tool in the public health arsenal to help predict when and where outbreaks may strike – including monitoring sewage. Wastewater-based epidemiology, as it would come to be known, garnered national attention in the University of Arizona's effort to bring students back to the classroom. And in Yuma County, where 90% of the nation's wintertime vegetables are grown, wastewater monitoring helped keep the agriculture industry operational during the pandemic.    

Now, researchers at the UArizona Yuma Center of Excellence for Desert Agriculture are turning to wastewater monitoring to help defend against yet another emerging public health concern, the drug-resistant fungus Candida auris.

A serious fungal disease that is rapidly spreading in hospitals and health care facilities across the United States, Candida auris can cause bloodstream infections and even death in patients with serious medical conditions.

"The Arizona Department of Health Services is partnering with YCEDA (Yuma Center of Excellence for Desert Agriculture) to test wastewater for Candida auris as a pilot monitoring program," said Bradley Schmitz, a visiting researcher with the center's molecular biology laboratory and a national expert in organizing and executing wastewater-based epidemiology programs.

The research team hopes the project can help establish a standard method for monitoring Candida auris in wastewater that can be deployed statewide. The data collected will help inform public health criteria for directing prevention resources.

In the last month, the Centers for Disease Control and Prevention reported that clinical cases of Candida auris infections have nearly tripled since the onset of the COVID-19 pandemic, bringing about comparisons to  the hit HBO show "The Last of Us," in which a fungal pathogen causes a doomsday scenario and the end of civilization as we know it.

Far from the fictional apocalypse of prime-time television, Candida auris likely poses no risk to people who have competent immune systems, Schmitz said. However, it could be deadly for others.

"Those with indwelling devices, including ventilated patients or those with central venous catheters, and immunocompromised individuals could develop severe infections and even die from C. auris," he said.

The Centers for Disease Control and Prevention has identified Candida auris as an "urgent threat" because 90% of infections are resistant to at least one antifungal medication, and some are resistant to every available antifungal class.

Its multidrug resistance has led to outbreaks in health care environments, especially hospitals and long-term care facilities, and many patients do not show symptoms of Candida auris colonization, Schmitz said.

"Wastewater-based epidemiology is a unique and perfect approach to identify C. auris in these community populations, because even asymptomatic carriers of the drug-resistant fungus can be identified in wastewater," he said. "Therefore, wastewater monitoring can support early-warning identification of positive individuals in a health care facility and prevent further spread of this dangerous, life-threatening organism."

Keeping 'America's salad bowl' growing

The effort builds on the Yuma Center of Excellence for Desert Agriculture's successful use of wastewater monitoring to help the Yuma community track the spread of COVID-19.

Nicknamed "America's winter salad bowl," Yuma is the No. 1 producer of the nation's wintertime leafy greens – such as romaine lettuce, spinach and kale. Hoping to avoid the COVID-19 outbreaks that plagued the meatpacking industry, growers and Yuma community members banded together early in the pandemic to bring wastewater-based epidemiology to their county.

Schmitz, who studied under renowned UArizona environmental microbiologist Ian Pepper, was instrumental in expanding the Yuma Center for Excellence in Desert Agriculture's wastewater-based epidemiology program, designing the Arizona Department of Health Services-sponsored Yuma County COVID-19 Community Protection Early Warning and Response Program.

The program established wastewater testing in Yuma County and its four municipalities to further inform public health officials and decision makers' targeted response plans to potential hot spots in their communities.

"We are located on the borders of Mexico and California and have a large migrant labor force, much of which crosses the international border every day. We have two large military installations and two tribal nations," said Paul Brierley, executive director of the Yuma Center of Excellence for Desert Agriculture. "The municipalities, the hospital, the schools, the ag industry, the military and others all work very well together as a community to tackle the many issues they share."

Using wastewater as a first-alert system for the presence of COVID-19, the county was able to stay ahead of the curve and keep produce rolling out of the valley to consumers across the country.

A major tool in protecting public health

Beyond COVID-19, the Yuma center has expanded its wastewater monitoring program to help its community deal with other public health concerns such as influenza; respiratory syntactical virus, known as RSV; and now the drug-resistant fungus Candida auris.

Brierley attributes the Yuma center's success to its ability to pivot quickly to tackle emerging concerns, employing professional staff, and partnering with national and global visiting researchers to work together with industry and government collaborators and "get the job done."

"We are honored to have a strong multidisciplinary team who work in the many facets of public health that wastewater-based epidemiology demands in order to be effective," Brierley said.  

Alongside Schmitz and staff at Pepper's Water & Energy Sustainable Technology Center, the Yuma center also hosts Gabriel Innes, an epidemiologist and visiting research expert on antimicrobial resistance and health care-associated pathogens, as well as Andrew Patton, an epidemiologist and exposure scientist who has broad spectrum public health experience with an emphasis on predictive modeling.

The research team has worked to keep the Yuma Center of Excellence for Desert Agriculture at the forefront of wastewater-based epidemiology's potential, including working with the Southern Nevada Water Authority and the School of Public Health at the University of Nevada, Las Vegas, to build a community-scale wastewater surveillance program during a Candida auris outbreak in Nevada in the summer of 2022.   

"We were the first in the country to detect C. auris in wastewater with direct links to affected individuals and we will be the first with public health criteria associated with detection," Schmitz said. "Together and in conjunction with our core team at YCEDA, we're committed to a multipronged approach to deliver science to action."

The success of wastewater monitoring during the COVID-19 pandemic, in many ways, proved its validity in helping to direct public health efforts and clinical diagnostic testing to help bring the world back to a sense of normalcy, Schmitz said. Now a more trusted public health tool, it is poised to help prevent future pandemics. 

"We believe wastewater-based epidemiology is the next major tool for protecting public health and making an impact on communities throughout the state and country," Schmitz said. "We could not do this without the support and collaboration of our partners, who have translated our science to action, preventing illness and disease-related death."