Researchers at MIT start-up Biobot have a high-minded assignment for the waste that ends up in the sewer system after being flushed down the toilet. “Our mission is to transform wastewater infrastructure into public health observatories,” says the group’s website.

Based on copies of the coronavirus found in samples from the sewer system in New Castle County and in Wilmington, Biobot estimates there were 15,200 cases of the virus in the county as of April 15. The total number of cases confirmed by the state Division of Public Health was 974 on April 15.

The Division of Public Health did not have a comment on the report. A spokeswoman said they were not aware of the study.

“We must do whatever we can to keep communities safe, and we must do it today,” New Castle County Executive Matt Meyer said. “This is a data point that may [us] help better understand the prevalence of COVID-19 in our community. Anything that helps make this invisible enemy a little more visible is welcome.”

Because clinical testing of patients has been slow and many people who have the virus don’t show symptoms, Biobot’s testing may give a better picture of what the actual case number is.

According to the Centers for Disease Control and Prevention, the coronavirus has been detected in feces of some patients; “the amount of virus released from the body (shed) in stool, how long the virus is shed, and whether the virus in stool is infectious are not known.”

The CDC says the risk of transmission of the virus via feces is not known, but “the risk is expected to be low based on data from previous outbreaks of related coronaviruses.” There has been no confirmed fecal-oral transmission of COVID-19, according to the CDC.