With the Boston-area bracing for an influx of more coronavirus cases, what travels below the cities' streets could give us the clearest picture of an uptick in cases.
"Everybody has a voice in the sewer," said Mariana Matus, cofounder of Cambridge-based Biobot.
Biobot is testing the wastewater at the Massachusetts Water Resources Authority's Deer Island wastewater treatment plant. The company, the first in the United States to try this approach, has shown it can give an early indication of a rise in cases based just on what's in sewage.
"Every time we are flushing the toilet, we are creating a high quality medical sample," Matus said. "It is very unbiased. It includes people who have not been diagnosed, it includes people who may be asymptomatic or refuse to go to the doctor, it is very inclusive, and therefore it is a very good test of what is happening."
Biobot has found higher traces of COVID-19 in recent tests, which are conducted three times a week. Experts sounded the alarm over the data earlier this fall.
The company got its start in 2017 testing for traces of drugs in Boston's water.
"We actually started testing for opioids because that was considered the No. 1 public health priority in the country. In March, we pivoted," Matus said.
March is when the Boston area started getting hit hard with COVID cases, in a surge that lasted into May, shutting schools, businesses and much of public life as the pandemic took hold locally.
Biodot's data, posted to the Massachusetts Water Resources Authority's website, has shown steadily increasing traces of the virus the Boston area since early October. Current levels are nearing where they were in April, the height of the first surge.
And COVID case numbers are on the rise as well. More than 2,000 were reported on Tuesday, numbers which, until last week, hadn't been seen since May, as the surge was receding.
"I am worried," said Dr. David Hamer, a Boston University professor of global health and a practicing doctor. "This is a signal that we need to ... adhere to our protective measures and perhaps enhance them also."
Forty-three communities from eastern Massachusetts have their water treated at the plant, including Boston, Cambridge, Framingham and Quincy.
Together they have accounted for 40-50% of Massachusetts' coronavirus cases, the Massachusetts Water Resources Authority said in June, while announcing a $200,000 contract for a wastewater study at the treatment plant "as an early warning system tracking trends and potentially predicting a second wave of COVID-19."
The data extracted from Deer Island cannot be linked to specific cities, towns or neighborhoods, but it is providing public health officials with a big-picture outlook of what is going on in the region.
"A public health platform built on that data has the potential to make public health way more proactive and not just wait to see what happens in hospitals," Matus said.