How can we act on the waves of COVID counts and future pathogens? Wastewater can tell.
New coronavirus cases reported to the state of North Carolina have reached their highest numbers since the winter, but the reported number still doesn’t reflect the level of coronavirus being found in wastewater.
COVID transmission could once again surge while NC cities — regardless of their level of community spread — haven’t made a push on public masking as they did in the winter.
As a next and possibly more effective step to help individuals make decisions on personal protection, the government could turn wastewater surveillance into local risk forecasting, according to researchers at the University of North Carolina who lead NC’s wastewater studies.
UNC microbiologist Rachel Noble has been working on COVID testing in wastewater since early 2020. Her lab collaborates with other academics, the state Department of Health and Human Services, and wastewater utilities to build the COVID surveillance framework.
NCDHHS overhauled its COVID severity metric earlier this year by elevating wastewater measurement up to one of the major factors. The wastewater data is updated every Wednesday on the DHHS dashboard.
About 25 wastewater utilities now collect and test for coronavirus concentration out of NC’s over 100 sewage systems. Noble’s lab has been testing the majority of the wastewater samples and providing data for DHHS.
Testing wastewater for viruses and pathogens is designed to reflect the full extent of community disease. Infected people, even those showing mild or no symptoms, shed the virus into wastewater, which is sampled for the lab to analyze.
The COVID-19 wastewater surveillance originally served to detect outbreaks before clinical results. As testing and reporting decline due to a lack of funding or the public’s fatigue with hiding from COVID, wastewater monitoring may become what people can use to determine daily risk levels.
Similar to the severe thunderstorm warning system, disease risk categories could help people decide how to protect themselves when their locality is threatened by outbreaks with a much more timely warning.
The alert could include regional recommendations and be carried by television and radio stations, regional newspapers, and cell phone apps.
“Not everybody can look at a graph [on the website] and understand what’s going on. We need a way to interpret it for the public so they can understand the risk to their everyday lives,” Noble said.
The concept of disease risk categories from wastewater viruses has not been pursued very long and will need some effort for researchers to develop, she added.
Diverging virus waves
DHHS continues to record and report positive COVID-19 tests while acknowledging that the number does not reflect the full extent of disease spreading in the community. The current community level calculation using case numbers underestimates the transmission.
The number of coronaviruses in wastewater has increased in some cities, but this trend has not been reflected in clinical reports.
The “missing” infections take many forms, including the prevalence of at-home tests that are not reported to DHHS.
Tourists can also contribute to the gap. They may shed the virus when they are visiting but not become ill or test positive until they return home.
Cities with airports like Charlotte and Raleigh, where passengers come in and out, may also experience an increase in viruses in wastewater that’s not always reflected in case reports.
Viral counts in wastewater
DHHS data shows that the recent surge largely has been caused by the omicron subvariant BA.5. The variant has a very strong transmission ability that breaks through the vaccines and boosters protection, and prior COVID infection immunity.
Regardless of the severity of COVID symptoms, when a person uses water and flushes it down the toilet, the viral material travels to the wastewater treatment plant. The trip takes only several hours to less than a day.
Wastewater utilities could collect untreated sewage for 24 hours, which would accurately capture the community’s daily activities. Noble’s lab can finish counting the COVID particles usually in less than a day after receiving the wastewater samples.
Researchers can also use this testing to detect many more future pathogens, including the yet emerging COVID variants and the recent spread of monkeypox.
“We are capable of monitoring monkeypox and we’ve been asked by the state to do the testing,” Noble said.
They didn’t detect monkeypox DNA in the wastewater samples in the past couple of weeks. It is unknown how many cases must occur in a given area before detection in wastewater is possible.
Noble’s lab receives tons of bottles filled with dirty water every week from over 20 wastewater treatment plants across NC. Each bottle represents a population that ranges from a few thousand in Beaufort up to hundreds of thousands in one of Raleigh’s plants.
As of the end of July, Noble’s team has worked intensely at their Morehead City lab to test and analyze wastewater for 80 weeks in a row.
Noble said wastewater surveillance will be more valuable in areas where medical facilities are scarce. Her team has increased the number of plant locations in the past years to include more rural regions and she hopes to continue expanding the service of wastewater surveillance.
“If medical facilities are not as plentiful to the people, they will not be tested. And if they’re not tested, they’ll not be reported as positive cases,” she said.
Noble’s team also works with DHHS and CDC, teaching them how to translate the data for everyday use.
“We’re trying to work with them to create more [relevant] information for the public,” she said.
