In the past, Mia and Amy have worked together to trace outbreaks of disease back to contaminated water in places like lettuce farms and water parks. What they’re doing now is the flip side to their previous work—starting with contaminated water and using it to identify pockets of illness. When people get infected with COVID-19, pieces of the virus can be found in feces. So when researchers like Mia and Amy find those bits of virus in sewer water, “we know there’s somebody in that community who has COVID-19,” Mia says. By taking many samples over time, they can watch whether the amount of virus in those samples is going up or down. That might tell local health departments whether an outbreak is getting better or worse—or provide an extra insight when other data are murky. “The trends in the sewage concentration have been shown to be a leading indicator in numbers of cases,” Mia says. “When the number of COVID-19-positive samples in sewage go up, 3 to 7 days later, the number of reported cases go up.” Although this approach to identifying COVID-19 is still experimental, the science is not. Wastewater surveillance has been used in countries where polio is still a threat to look for evidence of polio in a community. In the United States, it’s been used as a way to estimate opioid drug use in a community by testing sewage for chemicals left behind after the body digests those drugs. Amy and Mia are still trying to work out some details, such as how the amount of virus in a sample relates to the number of cases in people and how fast the virus can decay in wastewater. But tests across several states are under way. If successful, they hope this approach could be used as an additional tool for the current pandemic, as well as to look for other health issues, such as foodborne illness or resistance to antibiotics.
