Peering down into storm inlets, walking near swales following a heavy rain or pulling up a chair at the plant headworks will give you a good look at what is coming into your local wastewater treatment plant. But what about the things you cannot see? In the face of new and potentially widespread pathogens, the application of wastewater surveillance is getting renewed focus as a proven low-cost technique for getting ahead of outbreaks.
Along with other municipalities around the world, New York state explored the benefits of testing wastewater for COVID-19 to track community spread in the fall of 2020. Studies show that this approach can reveal a pathogen’s presence in the community about 7 days before individuals start showing symptoms, enabling leaders and public health experts to respond and prepare their communities accordingly to prevent further spread.
The history of wastewater monitoring for public health
In the 1960s, researchers at Yale University first used wastewater surveillance to help evaluate the effectiveness of polio vaccination campaigns over time. From that initial research, the use of wastewater surveillance to evaluate population health trends spread internationally. In addition to Polio, wastewater surveillance has been applied to other pathogens like norovirus and hepatitis.
When the COVID pandemic started, universities around the world began studying how wastewater surveillance could be adapted to provide an early warning detection system for SARS-CoV-2 infections within a community, workforce or other population. The attraction related to the ability to capture a pooled sample to assess the presence of infections in the population, potentially helping accelerate prevention measures and reducing spread. In addition, it could help supplement other surveillance given limited clinical testing.
In most communities, monitoring pathogen outbreaks focuses on the visible immune response of sick individuals. However, this approach relies on sick individuals displaying symptoms, and that they were not contagious before displaying symptoms. Sick individuals can spread the pathogen a week or more before they have any visible symptoms. In addition, there are those that might be infected but remain asymptomatic, and there are those that will not take precautions despite their symptoms.
In the case of COVID-19, university researchers were determined to better understand the lower detection limits of the virus in wastewater. These limits compare the smallest number of infected people that can be detected within a collection system’s flow (polio could be detected at about 1 case in 10,000 people). Additional research also looked at the lack of a standardized analytical method (a topic around which there has been significant entrepreneurial effort); and the approach to normalizing and interpreting data. Sampling programs must be undertaken by groups that understand the analytical complexities and can simplify those to account for the population and collection system in question – it is not as simple as just grabbing samples and sending them to a lab. Read more about the process and disciplines that must be involved in a viable program here.
A resilient future with wastewater detection
As the availability of viable COVID vaccines improves, it may seem that the necessity for wastewater surveillance might wane. However, the virus will not simply disappear and even as it comes under control. It could be years before it is effectively eradicated. At the same time, the potential for other new virus threats and monitoring needs are very real. Climate change threatens to increase the range of certain disease-carrying insects, and potentially allow long-dormant viruses to emerge from the ground. Organizations like the European Monitoring Centre for Drugs and Drug Addiction have also used the technique to monitor for drug use (i.e. opioids) in communities.
With this in mind, wastewater surveillance is still an effective tool to support the long-term resilience of a population. At a minimum it can be baked into continuity planning with well thought out triggers. It could also be a tool to optimize the cost, effectiveness and flexibility of an ongoing or phased monitoring program. As we return to work, universities and schools, traveling via public transport, and participation in social interaction, monitoring programs that stay ahead of public health can continue to protect communities and businesses alike.
