Wastewater Testing for Arboviruses: Arizona’s Surveillance Approach

May 06, 2026 | Sidnie Christian

Wastewater surveillance, also known as wastewater-based epidemiology, has emerged as an innovative way to track community health by analyzing what goes down our sinks and flushes down our toilets. During the COVID-19 pandemic, this approach gained global attention as scientists used sewage samples to detect and monitor the spread of COVID-19, often days or even weeks before clinical cases presented for care. As health departments recover from the strain of the COVID-19 pandemic and prepare for future threats, many are exploring other applications of wastewater surveillance, including the detection of arboviruses.

Arboviruses are viruses transmitted by mosquitoes, ticks, and other arthropods — such as West Nile virus (WNV), dengue virus, and St. Louis encephalitis virus (SLEV) — continue to pose seasonal threats around the world. Surveillance for arboviruses relies on clinical laboratory testing, public health investigations, and mosquito trapping/testing. However, these methods can be resource-intensive, are sometimes delayed, and may not account for asymptomatic individuals. Utilizing wastewater as a tool to detect arboviruses is a potential emerging area of opportunity for public health that may complement current surveillance efforts — and Arizona is one jurisdiction leading the charge.

Confronting the Arbovirus Disease Burden

The Arizona Department of Health Services (ADHS) developed an initiative in response to its arbovirus disease burden, particularly from WNV, dengue virus, and SLEV. These viruses are endemic to the area and continue to pose a significant public health threat.

Following the persistent seasonal impact of WNV and the reemergence of SLEV after the 2015 outbreak, the agency recognized the need for improved tools to detect viral circulation in a timely manner — particularly because people infected can experience little to no symptoms and, therefore, may not seek medical care. In response, the Arizona team is piloting wastewater testing to detect arboviral activity at the community level, to potentially provide an additional early warning signal that may inform vector control, public messaging, and partner coordination. While still in its infancy, the program shows potential to enhance detection and improve response timeliness.

“We felt there was a need to focus on developing an enhanced surveillance strategy, such as wastewater surveillance, to assist with our existing efforts and to add another tool to our toolbox to assist with monitoring for the disease.”

Promising Early Results

The Arizona State Public Health Laboratory has developed an in-house multiplex assay targeting WNV, dengue virus, and SLEV. To ensure the assay was both sufficiently sensitive and specific, the team evaluated it across multiple targets. Preliminary testing using frozen samples has identified multiple positive wastewater detections. In addition, several trace detections (nonzero but below the limit of detection) were also observed — many for WNV and dengue virus, while SLEV was less frequently detected. More information is needed to determine if the difference in detections reflects differences in assay performance, lower environmental transmission, or differences in viral shedding into the sewer shed.

Although the laboratory has completed preliminary validation of the assay, the relevance of these trace detections remains unclear and requires further investigation. To better understand whether these low-level signals represent true positives, the Arizona State Public Health Laboratory is exploring the use of next-generation sequencing technologies as real-time testing is implemented.

For the pilot program, sampling occurs approximately twice a week, similar to the approach for wastewater surveillance of other pathogens. Discussions with ADHS’ Vector-Borne & Zoonotic Disease team informed site selections, targeting broader areas with higher observed mosquito activity as well as areas with lower activity for baseline comparisons. This approach allows for a better understanding of detection patterns and assists with evaluating the effectiveness of monitoring efforts. The program is still in its early stages, and the team will collect more data in the coming season. However, these early data are encouraging, as they suggest that the lab’s approach could augment disease detection and provide a head start in monitoring outbreaks.

“All of our preliminary tests have performed very well, and we were surprised by how many trace detections we observed. Further real-time testing and confirmatory methods, such as sequencing, will be needed to determine their significance.”

Infrastructure Needs

Sustaining the program relies on both funding and laboratory capacity. Funding supports resource development, staff, instrument maintenance, and other operational laboratory needs. The laboratory team has been integral to this project, developing specialized testing methods in close collaboration with epidemiology staff and fellows from the Association of Public Health Laboratories’, while contributing essential technical expertise.

“Our lab has been crucial for this, and we have to give big kudos to them for developing these wastewater testing methods and supporting the project every step of the way.”

The arbovirus wastewater surveillance initiative is built on strong partnerships among state and local public health teams and utility partners. The wastewater surveillance program staff work closely with the state’s vector-borne epidemiology team and the state public health laboratory. At the local level, the Arizona Wastewater Monitoring Program engages with its points of contact for wastewater surveillance as well as county staff involved in mosquito surveillance testing. Coordination with local health departments has been instrumental in identifying wastewater sampling sites, understanding the data, and determining next steps. If an arbovirus is then detected in wastewater, the local health department will work with the ADHS wastewater team and the vector-borne disease coordinators to understand the interpretation of the positive result, and determine the appropriate next steps.

Finally, ADHS proactively communicates any arbovirus testing efforts with utility partners who provide valuable expertise on the watershed and prove vital to the sampling process. Maintaining this broad network of partners supports coordination, ensures that all parties involved are informed, and facilitates integration with existing monitoring efforts.

“More data will help us better understand where and how this surveillance can be most useful, and we plan to work closely with all our internal and external partners to figure that out.”

Communications

At this stage, communications have primarily focused on keeping local partners informed of updates and progress. However, in preparation for potentially adding these new pathogens to routine testing, the ADHS Wastewater Monitoring team is proactively developing resources and documentation, including pathogen-specific talking points, checklists, and decision trees. They work closely with subject matter experts to refine this suite of tools to guide ADHS staff on how, when, and what to communicate in the event of detections.

They also look to their peers in other states and adapt existing resources, such as North Carolina’s measles decision tree, which served as a model for ADHS’s arbovirus wastewater response planning. Having these tools ready is especially important in helping ADHS staff who are not engaged with wastewater monitoring understand its implications.

“Our goal is to ensure that internal communications are clear and actionable, providing guidance for both our team and local health partners so that detections translate into meaningful public health action, not confusion, as the program grows and generates more data.”

Looking Ahead

The ADHS Wastewater Monitoring team emphasized the potential for this surveillance approach to complement other surveillance systems and serve as an early indicator for public health action. Application of wastewater monitoring to arboviruses is novel and the ADHS team recognizes that this is a learning process, anticipating opportunities to refine strategies over time.

“We’d love for it to be that early indicator, where it can support messaging, vector control activities, or other interventions before cases are detected. [Wastewater surveillance] really enhances the ability to reach providers and schools or inform public health planning.”

For other jurisdictions considering wastewater surveillance for arboviruses, the ADHS Wastewater Monitoring team recommends planning ahead. Developing pathogen-specific resources (e.g., talking points, checklists upon positive detection, and response guidance) before testing begins ensures that all internal and external partners have the information they need up front and tools to evaluate wastewater data.

In Arizona, mosquitoes can spread viruses like WNV, dengue virus, and SLEV, and rapid detection is key to supporting timely public health intervention. This innovative work in Arizona might help demonstrate when and how wastewater monitoring could add value to arboviral surveillance.

Reviewed by Meredith Allen, DrPH, MS, Vice President, Health Security; Kate Petersen, MPH, Senior Director, Infectious Disease Infrastructure & Policy; Erin Laird, MPH, Director, Emerging Infections.