Could wastewater indicate the next Covid-19 hotspot?
You know those “viewer warnings” that appear at the start of some television shows? Well, consider this a reader warning. The “eewww” factor may show itself in this story, because wastewater can tell health officials a lot about the novel coronavirus that causes Covid-19.
Yes, you read that correctly. Wastewater. As in, what goes down the toilet, down the shower drain, and down the drain in the sink.
Here’s why what is found in that water is important.
Filling in the gaps left by asymptomatic carriers
One of the challenges in fighting Covid-19 is that people who have the virus don’t always show symptoms. That’s what is known as being asymptomatic.
And you can imagine the danger. People who have the virus can spread it unknowingly because they feel fine and there’s nothing to indicate they are contagious. They don’t have the usual symptoms of infection with SARS-CoV-2; high fever, loss of taste or smell, cough and congestion, so they don’t get tested to know if they have the virus and should quarantine because they don’t think there’s a reason to.
There’s also the challenge of people who may feel mildly ill but don’t get tested either because they don’t have a medical provider, or that provider doesn’t have tests, or the patient has no way to get to a testing location.
It all means state and local health officials have an incomplete picture of where and how the virus is being spread.
How pathogens get into wastewater
“When the virus gets into someone’s body, their body actually produces more of the virus; in their nasal passages, their saliva, and throughout their gut,” said Rachel Noble, a professor of marine and environmental microbiology at the University of North Carolina Institute of Marine Science in Morehead City.
“Wastewater can be used to learn whether the pandemic is effecting entire communities, because we recognize that there’s a whole portion of the population in any given town that’s being missed because they might be mildly ill or asymptomatic.”
It’s what is known as wastewater-based epidemiology (WBE).
Noble and her research team have studied other viruses in wastewater and have developed technology to apply rapid diagnostic methods to wastewater, marine and freshwater recreational waters, and other systems like seafood and shellfish.
They are using the same technology to track SARS-CoV-2.
“The idea is that using wastewater allows you to measure the prevalence of the virus using the concentration value — the numbers of the virus in the wastewater,” Noble said. “And it tells you something more about the community or the entire system of people that is feeding into the wastewater.”
Preview of where the virus is spreading
Human waste by a sewage treatment system goes to a single location. By sampling the waste collected at these systems over a 24-hour period, whether it be a municipal facility or a smaller system for a specific development, researchers get access to what is happening in the entire population.
That information can help predict whether the number of cases may be rising, falling, or staying steady.
“If the wastewater data is showing an upward trend then in around six or seven days the clinical cases are doing the exact same thing,” Noble adds. “We’re basically getting a preview.”
Samples are being taken from 18 wastewater treatment systems, including Beaufort, Newport, Morehead City, Wilmington, Charlotte, Raleigh, Durham, Cary and Greenville.
There are not enough resources to collect samples from septic systems. That’s a future and important goal, because more than 60% of the state’s population is served by septic systems.
For now, Noble says the goal is to develop a system that can identify potential coronavirus hotspots as well as highlight ways to control the virus.