COVID-19 wastewater surveillance ‘is more important than ever’

As many states and major cities roll back COVID-19 safety measures, wastewater surveillance will become a key information resource for monitoring and controlling the endemic phase of the pandemic. 

Northwestern University professor Aaron Packman is available to comment on the importance of long-term wastewater surveillance to monitor COVID-19 outbreaks and prevent future pandemics. An expert on water systems and waterborne disease transmission, Packman also can explain how wastewater surveillance works and why it’s now “more important than ever.” 

Packman is a professor of civil and environmental engineering in Northwestern’s McCormick School of Engineering and director of the Center for Water Research. He also is the lead data analyst for the Illinois State Wastewater Surveillance System, a cross-institutional effort led by Northwestern, the Discovery Partners Institute, University of Illinois-Chicago, Argonne National Laboratory and the Department of Public Health. The multidisciplinary team samples, tests and analyzes wastewater from sources around Illinois. Using trends in wastewater data determined by the team, the Illinois Department of Public Health makes decisions on where to deploy more public health resources, including testing sites, vaccine clinics and extra hospital staff.

Packman can be reached directly at a-packman@northwestern.edu.

Q&A with Professor Packman:

What are the advantages of wastewater surveillance?

“Wastewater surveillance provides an easy, inexpensive and passive way to determine if the COVID pandemic reemerges after restrictions are lifted. So we have a very easy way to determine an increase in COVID cases that doesn’t depend on individuals getting tested.

“It’s far, far less expensive than testing individuals because all the infrastructure is already there. Wastewater is sampled every day and tested for a whole range of things. So we just need an additional sample for analysis. That one sample represents millions of people, and it’s completely anonymous. It’s the most efficient surveillance method. And now that we are ending restrictions and mandates in Illinois, wastewater surveillance is more important than ever. It’s passive surveillance that we can do in the background, without bothering anyone.”

How long does it take to process a sample?

“Sampling can take a couple days. But keep in mind: How often do you get tested personally for COVID? Most people with COVID infections don’t get tested until they have symptoms, which can take up to five to seven days to appear. And some people who are asymptomatic might not get tested at all. Part of the advantage of wastewater surveillance is its passive nature. People start shedding the virus before they are sick.

“It helps that we have this statewide Illinois wastewater surveillance system, so we’re collecting samples twice a week at locations around the city and state. We can get a good ongoing estimate of cases.” 

How does SARS-CoV-2 show up in wastewater?

“People generally think of COVID as a respiratory infection. But in about one-third of COVID cases, people experience gastrointestinal symptoms. And a definitive feature of COVID is that infected people shed this virus everywhere. This virus replicates really well and affects many parts of the body. Even if you’re asymptomatic, you still release the SARS-CoV-2 virus RNA in your feces and your urine. So through wastewater surveillance, we can identify people who are sick — even if they don’t feel sick or know they are sick. We can find hidden COVID clusters.”

Where is wastewater surveillance most useful?

“Wastewater surveillance is useful in both large and small cities. In the Chicago metro area, wastewater surveillance covers more than five million people. In suburban and rural areas across the state, wastewater surveillance from multiple small and medium-sized municipalities provides information that guides County Health Department response efforts.”

How has wastewater surveillance been used in the past?

“Wastewater surveillance recently has been used to track opioids. We have very high sensitivity chemical analysis methods, so health departments were trying to identify areas of the city with opioid problems. Then they could allocate resources to help people who are addicted to opioids. Wastewater surveillance also has had some major successes in eliminating diseases, particularly polio. For decades, we had a massive campaign to stamp out polio. When we reached the end of that campaign, we wanted to know if there was any polio in a region. Wastewater surveillance played a role in that. Through wastewater, we could tell if there were any people with polio somewhere contributing wastewater to the system. It’s not like we can say there is one person sick or five people sick, but we get a relative measure to determine if it’s a low-level outbreak or more alarming.” 

How can wastewater surveillance prevent future pandemics?

“Even though we are still dealing with the immediate pandemic, there is still work needed to refine the sampling infrastructure.

“We have surveillance at O’Hare airport, and the airport authorities have been super helpful. We have surveillance at a couple domestic terminals and at the international terminal. It’s a different approach because you don’t have a resident population. The main focus there is genomic sequencing. You can take single samples on a busy day at the airport. You can sequence them to get some information all the different types of viruses or other pathogens that are present. That’s been very effective. The new omicron subvariant BA.2, for example, is very infectious and spreading around Europe. We have not had any outbreaks here, but we have detected it at the airport. So we know people with BA.2 are arriving here. The health departments are on alert. Then we can see if there is community spread from there. 

“Imagine if we had done this at the start of the COVID pandemic? We would have known exactly when COVID arrived. If we had a better, more refined system, we might have implemented quarantines and controls much, much earlier before it became a massive problem. That’s a part of the long-term strategy.”