Wastewater a key barometer of COVID-19, scientists say

If New Yorkers experience another COVID-19 surge this winter, scientists believe it will be wastewater, rather than diagnostic lab tests, that will provide the best early clues.

For more than two years, wastewater surveillance has served as a reliable bellwether for tracking the highs and lows of the pandemic, providing key information to state and local agencies about virus trends. 

Now scientists are taking the next steps with this vital information, using it to predict future hospital surges from the disease, collecting and processing samples to monitor the genetic material that measures and predicts the virus in Long Island's population. 

At the same time, wastewater has also been key in helping track the presence of poliovirus in Nassau County and other parts of the state.

“This is really a tool that we’re just starting to scratch the surface on,” said Christopher Gobler, director of the New York State Center for Clean Water Technology, part of the New York State Wastewater Surveillance Network.

Waste: Historic tracker of illness

The idea of using human waste to track dangerous pathogens can be traced back to the cholera epidemic in 1850s London, said David Larsen, an epidemiologist and associate professor at Syracuse University who is the principal investigator at the state’s Wastewater Surveillance Network.

John Snow, an English doctor known as the “father of epidemiology,” determined a cesspool was leaking into a water pump, tracing the path of what was causing cholera at the time.

Wastewater was also used to track typhoid and polio in the early 20th century.

And in more recent years, Europe has used the surveillance method to estimate drug use across the continent, he said.

Now, wastewater surveillance is more important than ever in helping track COVID-19, according to Gobler and Larsen.

For much of the COVID-19 pandemic, test results were meticulously cataloged and documented — providing important information on the path of the disease caused by the SARS CoV-2 virus. But over the last year, at-home COVID-19 tests have become more common and the results do not need to be reported. That means test results reported by the state and federal government are not capturing the full spread of COVID-19 in any given community.

In addition, wastewater captures evidence of the virus from people who may not have symptoms or even know they are infected, Larsen said.

“You can be a carrier of a virus and transmit it to others without knowing it or you could be someone who doesn’t have access to health care or can’t leave work, so you never get tested,” Larsen said. “But all those people use the bathroom. And the virus is shed in the feces that comes through in the wastewater.”

According to the state Health Department, wastewater surveillance can detect the virus in "as many as three to seven days" before those increases are found in the percentage of people who test positive or are hospitalized.

Gobler said the data from wastewater has proved to be reliable.

“There’s been these waves of COVID-19 that have come along with different variants and different seasonality,” he said. “One thing that’s been consistent is that we’ve seen surges in wastewater before we have seen surges in caseloads. That’s the whole reason for doing this.”

For example, Gobler said he expected COVID-19 caseloads to dip in the spring and summer of 2022 as they did during that same time period in 2021. But wastewater samples kept showing high caseloads on Long Island. He even asked his lab technicians to double check the results because levels in the community seems to be going down.

“There was yet another variant that was coming,” he said, referring to the emergence of the omicron subvariant BA.5. “That showed in the wastewater but not necessarily as much in the community.”

Tracking through network of collection points

In September 2020, the Centers for Disease Control and Prevention launched the National Wastewater Surveillance System, specifically to track the presence of SARS-CoV-2. Funding comes through the local health departments and is conducted through a network that includes laboratories at universities as well as commercial labs.

In New York, wastewater is collected at sites throughout the state at least once a week if not more, according to the New York State Wastewater Surveillance Network. On Long Island it is collected at eight treatment plants: Great Neck, Port Washington, Bay Park and Cedar Creek in Nassau County and Riverhead, Selden, Port Jefferson and Bergen Point in Suffolk County.

Larsen said samples are collected over a 24-hour period to be more representative of a community.

“Wastewater treatment plants do this normally as part of their routine to comply with discharge guidelines and EPA guidelines and requirements,” he said.

Then the wastewater is pre-processed.

“There's a lot of different methods and lots of different labs do different things,” he said. “That pre-processing condenses the amount of viral RNA or the amount of total nucleic acid into a smaller sample.”

The third step is conducting a polymerase chain reaction, or PCR, test to look for genetic material from the virus. These are the same tests conducted on people to see if they have COVID-19.

The lab Gobler operates through Stony Brook evaluates the Suffolk County wastewater samples and will soon take over the Nassau County samples currently handled through a commercial lab.

Results are documented at both the state and national levels. Maps on both the national and state wastewater surveillance web pages provide details on trends. The virus detection level for most of New York, including Long Island, remains “substantial to high.”

Larsen said labs in the state network are working on predicting COVID-19 hospitalizations within a county based on the amount of SARS CoV-2 RNA in wastewater.

“The laboratory methodology to build inference from data requires a bit of time,” he said. “We're getting ready to forecast hospitalizations and we're understanding the relationship between transmission and levels in the wastewater.”

Gobler said he could see a time in the future where treatment plants are outfitted with devices that would automatically detect viruses and other substances in the water.

“I believe this is a tool is that going to become more sophisticated and more widely used,” he said.