The following article was originally published May 12, 2020, and republished through a collaboration with KPCC and LAist.
Story by Sharon McNary
Thousands of us have done individual tests for the coronavirus, one swab at a time. But scientists plan to test entire communities for the virus by sampling something we collectively contribute — our poop.
That's right: Scientists propose to sample raw sewage at wastewater treatment plants as an early warning system of new coronavirus outbreaks in L.A. County.
Adam Smith, an environmental engineering professor at USC's Viterbi School of Engineering, was notified Tuesday that the National Science Foundation will fund a project that would measure the coronavirus in sewage and show when it is rising or declining in the population.
"Even if they may be asymptomatic they are still shedding the virus and it's entering our wastewater," Smith said. Some 30% to 60% of people with no symptoms excrete the virus.
"What we're trying to do is use it as a supplemental data set to clinical diagnostic testing to try and understand how many people in that community have the virus, (and then) using it to look at trends like an early warning sign."
FOUR LABS TO TRACE VIRUS IN WASTE
USC, North Carolina State University, Rice University in Houston and Howard University in D.C. will gather samples from wastewater plants in their respective areas.
Six treatment plants in Los Angeles County, including the Hyperion Water Reclamation Plant near Dockweiler Beach, would provide samples to USC's Smith for testing. Smith is hoping to receive contributions from at least one Orange County treatment plant as well.
They would grab watery samples as well as the more solid fecal material (poop) in raw sewage. Then the scientists would analyze it for the presence of the coronavirus' RNA.
This kind of wastewater-based epidemiology is going on in the Netherlands, Paris and Australia. In the Netherlands, the coronavirus was detected in wastewater just four days after the first case of COVID-19 was detected in the population.
WHY TEST IF THE VIRUS IS EVERYWHERE NOW?
The testing for coronavirus in sewage would be quite limited — it would occur only at the six wastewater treatment plants at the end of the sewage pipes. So, it's reasonable to ask what useful information could come from the testing.
The testing can establish a baseline of the amount of virus that existed at the height of L.A.'s outbreak. Samples have already been collected for a few weeks and stored under refrigeration, but no testing is occurring yet because Smith's lab at USC is still closed due to the stay-at-home orders affecting L.A. and the university.
"We're hoping that we can get access to our labs beyond just storing the samples in the freezer in the coming weeks and start analyzing," Smith said.
Testing, once it begins, is expected to track the eventual decline in the virus, giving a good idea of when it's safe to lift stay-at-home restrictions. After that, continued testing could show if there is an outbreak as people resume contact with each other, and help authorities decide whether to respond with new physical distancing strategies.
THE FUTURE OF SEWAGE SURVEILLANCE
At some point in the future, routine monitoring of wastewater for coronavirus and other pathogens could become a standard precaution to monitor for increases in diseases like COVID-19.
But the sewage treatment plants in our region are spread very far apart, so merely knowing that the level of coronavirus is climbing again doesn't help health workers pinpoint where in that plant's treatment territory it is happening. It's impossible to do contact tracing through a maze of sewer lines back to a toilet of origin.
But Smith said that if testing for coronavirus in sewage turns out to accurately reflect its presence in the population, those results could justify further projects to test for the virus at other points in the sewage pipeline network. And that could help identify the neighborhoods where an outbreak is occurring.
A startup group of epidemiologists and other scientists called Biobot is offering to map coronavirus in wastewater in many locations. It is soliciting local officials and wastewater treatment plant managers to sign on to what could become a vast network of data about the virus in sewage.
"We believe that sewage offers a unique opportunity to make public health more data-driven and effective and that the best technologists can improve society," the Biobot website says.
Learn more in this webinar from Andrew Revkin of Columbia University's Earth Institute.