Traces of COVID-19 can be found in wastewater up to two weeks before symptoms appear
Exact Scientific Services, a wastewater testing company based in Ferndale, began testing Lynden wastewater for traces of COVID-19 in June, and have been tracking infection rates using wastewater testing.
Once an individual is infected, traces can be found in sewage faster than they start showing symptoms, said Kent Oostra, CEO of Exact Scientific Services.
After establishing a baseline number of cases, Oostra’s company is able to detect spikes of the virus within a population days before regular COVID-19 testing, Oostra said.
“We have seen spikes and then about 10 days later, or two weeks later, we see an increase in the number of [reported cases],” Oostra said.
Wastewater testing is not able to determine the number of cases in a community, but it is able to help researchers determine whether cases are increasing or decreasing over time, said Christian Daughton, former chief of the environmental chemistry branch of the Environmental Protection Agency.
Wastewater testing is also able to detect individuals who are infected, but not showing symptoms, Daughton said.
Wastewater monitoring for COVID-19 can serve as an early warning for an increase in cases, Daughton said.
The University of Arizona conducted wastewater testing in a dorm and was able to find two asymptomatic carriers who were spreading COVID-19 through a combination of wastewater surveillance and human testing via nose swabs, Oostra said.
“Since the sewage will also detect asymptomatic people — those who never get sick — you’re going to have an indicator that won’t show up with human testing,” Oostra said.
Monitoring wastewater for traces of COVID-19 is difficult because infected individuals shed different amounts of the virus, and some won’t shed traces of the virus at all, Daughton said.
“Right now the figures you see thrown around are maybe 60% of infected individuals will excrete [the virus],” Daughton said.
Currently, Exact Scientific Services has only been given permission to test wastewater in Lynden, Oostra said. Exact Scientific Services has reached out to other cities in Whatcom County, including Bellingham, but has not received a response from any city other than Lynden.
“The big issue I run into right now is the government and the health departments don’t have a directive on how to use [wastewater testing],” Oostra said, “They’re still trying to figure that out.”
The Whatcom County Health Department is not involved in the wastewater testing in Lynden. Instead, it was decided by the city of Lynden, said Amy Cloud, public information officer for Whatcom Unified Command.
Oostra has been in contact with every mayor in Whatcom County, but has not yet received a response from any other mayor than Scott Korthuis, the mayor of Lynden.
The Whatcom County Health Department doesn’t conduct any wastewater testing for COVID-19, Cloud said.
“We are waiting for the [Centers of Disease Control and Prevention] and state Department of Health review and guidance on the use of wastewater testing results in overall COVID-19 surveillance and response,” Cloud said.
The CDC has awarded a grant to the Washington State Department of Health to begin testing wastewater sampling, Cloud said.
“We’ll be looking forward to finding out what this and other studies tell us about how useful sewage testing is for tracking COVID-19,” Cloud said.
“The city of Bellingham is aware of and following efforts locally and nationally regarding COVID testing in wastewater,” said Eric Johnston, director of administration and engineering for the city of Bellingham. “The City supports efforts led by the state and local health officials and welcomes any researcher looking to acquire samples from the city of Bellingham system.”
Wastewater testing has been used since 2001, mostly to test for traces of drugs and monitor the use of different drugs, Daughton said. Since creating the process in 2001, Daughton and other scientists have expanded the use of wastewater testing to monitor signs of disease in sewage as well.
Testing wastewater for a known virus like COVID-19 is helpful for tracking infection rates, but wastewater testing can also be used to find new viruses in the future, Daughton said. Using wastewater testing to monitor for future diseases and pandemics would allow scientists to identify and isolate hotspots faster than with human testing alone.
“If you had wastewater testing at the outset, you would just be able to monitor maybe major metropolitan sewage treatment plants, and just keep waiting until you see a signal [of the virus],” Daughton said.
Being able to show the trends in COVID-19 cases before human testing can also encourage people to wear masks and continue social distancing, Oostra said.
“One of the things that we didn’t think of is that the knowledge made it real for people,” Oostra said. “That number gives people real information to make a real decision.”
Oostra said he hopes that COVID-19 data from wastewater testing will also help inform decisions about COVID-19 protocols if testing becomes more widespread.