Flushing Out the Virus—Using Our Sewage to Monitor COVID-19
You’ve probably been reading news coverage of a number of studies trying to determine if sampling sewage flowing into treatment plants can provide early detection of the presence of the virus (SARS-CoV-2) that causes COVID-19 in communities. When you flush your toilet in Cook County, did you know you're contributing to that research? (You can insert your own snarky exclamation here—I’ll delicately decline to do so.)
In any event, I wanted to share what we know so far and what the Metropolitan Water Reclamation District (MWRD) is doing to assist several research studies underway. I’ll also describe efforts by a team at Northwestern University to develop a new rapid test that can be widely deployed to detect the presence of the SARS-CoV-2 virus in sewage samples.
First, let’s remember that human waste—urine and feces—contains trillions of bacteria, viruses, and other potential pathogens. Always has. Waterborne diseases from untreated water used to plague large cities (and still do in many places), which is why the invention of more modern sanitation and sewage treatment has been viewed as one of the most significant contributors to today’s longer life spans.
The sewage flowing into a wastewater treatment plant—called influent—contains information not only about the presence of diseases in communities, but also about pharmaceutical use, genetic information, and so on. Indeed, mining the data embedded in sewage influent may be the next frontier in resource recovery. (Researchers once sampled sewers surrounding a college campus in Washington state to determine if amphetamine use was higher during midterm and final exams. It was.)
Now, scientists believe that screening sewage can offer clues about how and where the SARS-CoV-2 virus spreads on a larger and less expensive scale than testing individuals, helping shine a light on the extent of the pandemic by complementing data from nasal swabs and antibody tests.
What Sewage Surveillance Can Do
- People with COVID-19 begin shedding the virus as soon as three days after infection, whereas other symptoms may take longer to develop. This means there may be a signal in sewage before people begin to seek care or get tested. Sewage samples from two treatment plants in the Netherlands showed presence of the virus six days before the first reported case (here is an interview with one of the Dutch scientists). Trends in the concentration of the genetic material in sewage might give clues about whether the outbreak is declining, or whether a second wave is on the horizon. Scientists at the Hampton Roads Sanitation District in Virginia have shared this visual example of how they use these data to identify trends.
- Depending on the air temperature, distance to the treatment plant, and number of infected people in the area being monitored, researchers estimate tests can be sensitive enough to detect one infected person in a population of 100 (in warmer areas) to one in 2,000,000 (in cooler areas).
- Sewage monitoring will not completely stop the spread of the virus, but it can tell decision-makers when to consider restricting certain activities or stepping up contact tracing and isolation efforts. By anticipating possible waves rather than responding to them, decision-makers will have more tools available to them sooner, which could mean an improved quality of life for all of us during a future wave if pockets of outbreaks can be identified and quickly snuffed.
In late April, the Water Research Foundation convened a four-day virtual summit—international experts from research institutes, universities, federal agencies, professional organizations, and utilities (including a microbiologist from MWRD)—to discuss research questions and needs in sewage surveillance. The MWRD has been sending weekly samples to a research study at Stanford since early March.
Julius Lucks, Associate Professor/Associate Chair of the Department of Chemical and Biological Engineering, and member of the Center for Synthetic Biology at Northwestern University, has been seeking to develop a new way to detect trace pollutants in water using “biosensors.”
“Microbes, especially, are constantly surveillling their external and internal environments to see what’s changing. What are the molecular mechanisms that allow them to do that?” Lucks told me recently. “Can we repurpose what we learn from natural biology for use in our own environments?” Now, Lucks wants to harness these natural biosensors and rewire them to detect SARS-CoV-2.
Previously, Lucks and his team had been working with biosensors to detect plant viruses, such as diseases that harm various crops. They developed a set of inexpensive, easy-to-use test kits that don’t require a lot of equipment to operate. Assisted by a talented postdoctoral fellow, Dr. Khalid Alam, Lucks began to focus on water quality monitoring…and then came COVID-19. “Clearly there’s a big need for a low-cost, distributed diagnostic test and we can reconfigure biosensors to detect the COVID pathogen,” Lucks explained. “I want to send out testers with a little hand-held device and an array of test strips and test [samples of sewage] on site. We’re trying to change the scale of how you conduct these tests. These could be done on every street corner several times a day.” Gathering all this data would allow decision makers to pinpoint where a local outbreak may be occurring and to enact containment strategies in that area.
Lucks and Alam formed a company called Stemloop which, with Northwestern, has received a grant from the National Science Foundation for its COVID-19 research. “We’re using the Center for Synthetic Biology’s expertise in computational modeling to simulate how biosensors work and design experiments. Many people think the pandemic is not a single eruption,” Lucks added. “It will come back.” Indeed, Lucks and colleagues at Northwestern and Argonne National Lab are gearing up to be able to test samples with the help of MWRD.
One important caution: there is currently no evidence to suggest that people can become infected with the SARS-CoV-2 virus through contact recreation, such as canoeing or kayaking in waterways where combined sewer overflows or broken sewer pipes have flushed raw sewage, or through professional work at a treatment plant or laboratory. The virus does not survive the wastewater treatment process or the water filtration process. (See this recent paper from the New York State Water Resources Institute for more.)
Wash your hands. Wear a mask. Stay tuned for more reports from the water front.
Celebrate the Summer Solstice
For the last 15 years, I’ve hosted an event to celebrate the summer solstice and to raise funds to support my campaigns and my work as a Commissioner on the Board of the MWRD (money to support publication of this newsletter, for instance, my annual report and public outreach, principally).
Not this year, alas. Instead, I invite you to raise a glass of your favorite water-based beverage—yes, beer qualifies—and celebrate with me, from a distance, the lingering light on June 20, the beauty of our natural world, the devotion of our best and wisest public health professionals, and the blessings of survival. You, my friends, are what makes my service worthwhile.
If you can support my work now, I’ll be grateful beyond words—and issue you a rain check to a future event, possibly next fall, when we can all gather together along the Chicago River and celebrate as we most wish to do.