A research team from the University of Michigan in Ann Arbor and Stanford University in California are studying whether COVID-19 can be detected in wastewater before cases spike in hospitals. Infected individuals shed viruses or viral genetic material in their waste.
The work is funded by a $200,000 rapid response grant from the National Science Foundation. Krista Wigginton, project leader and associate professor of civil and environmental engineering at U-M and a visiting professor at Stanford, has studied coronaviruses for the last several years. The virus family includes several strains of the common cold and other viruses. Not much is known about their presence, persistence, and transfer in the environment.
“One of the key areas we’re exploring is whether we can detect this new virus, SARS-CoV-2, in a community’s wastewater before it’s known to be circulating there,” Wigginton says. “The case numbers we’re seeing reported in the U.S. and lots of other places are dependent on how many test kits we have, so the curve displaying the number of cases is more of a curve of test kit availability in a community. What we see in wastewater may look totally different.”
Numbers outside of the tests could provide a clearer picture of how broadly the disease is spreading because it could pick up evidence of upticks in more mild cases or those who have no symptoms.
“For epidemiologists interested in the prevalence and incidence of COVID-19, our methodology offers an estimate that does not rely on testing every individual, nor is it as prone to measurement bias,” says Nasa Sinnott-Armstrong, a doctoral student at Stanford working on the project. “We could identify areas with rapidly increasing cases as a warning system to the health care system. Finally, these numbers can help epidemiologists model the trajectory of the pandemic with far less testing burden on our health care system.”
If the pandemic continues in waves, people working with wastewater could inform when it is necessary to head back indoors for another period of social distancing before ICU admissions spike.
“Having a better way to know when social distancing is required would be helpful,” says Alexandria Boehm, professor of environmental engineering, lead of the project at Stanford, and a senior fellow at the Stanford Woods Institute for the Environment. “Our hope is that we can detect an uptick in cases with this tool faster than we can through clinical testing. We don’t know that for sure, but that’s the hypothesis.
“It sounds to me like the earlier you halt the transmission in a community, the shorter periods of time you’ll need strict social distancing measures and the less inconvenient it will be for a community.”
Sewage surveillance already is used in Israel to monitor poliovirus circulation. In the case of COVID-19, the data also could provide insights into the diversity of viruses circulating in a community. Wigginton is not worried that COVID-19 would elude wastewater treatment processes. Previous research with coronaviruses suggests they are effectively removed with traditional water purification treatment steps.
The team has been collecting samples through the wastewater pathogen monitoring project at the Stanford Codiga Resource Recovery Center. Led by Craig Criddle, professor of environmental engineering and science, it’s a pilot-scale of wastewater treatment plant that treats sewage from Stanford’s campus. The team is also sampling in several nearby municipalities including Santa Clara County, where two of the nations’ first cases of COVID-19 were reported. They will begin analyzing the samples in the next few weeks.
Several other research groups are looking at wastewater as well, but so far, there are no reports of COVID-19 being detected. The U-M team has an advantage – Wigginton has previously published a study on recovering coronavirus from wastewater.
“In addition to collecting wastewater influent samples and archiving them, we’re also grabbing primary solid samples,” Wigginton says. “Our previous work suggests that these viruses stick to wastewater solids more than other viruses. We’re hopeful that we’ll be able to detect something.”
The researchers also will investigate how the virus responds to ultraviolet and solar light, which are potential disinfectants, and how and under what conditions such as temperature and humidity the virus transfers between fingers and inanimate objects. The latter research question will likely need to wait until universities can safely lift the current COVID-19 restrictions.
The project also aims to close some gaps in knowledge of enveloped viruses, which are encased in a layer of lipids, or organic compounds that aren’t water soluble. Environmental engineers explore the fate and detection of viral pathogens in the environment.
