With the virus’ rapid spread, and has inspired some researchers to look to wastewater to help fill in the gap of measuring how prevalent SARS-CoV-2 is in a given community.

In a paper posted Tuesday to the preprint server medRxiv, researchers collected samples in late March from a wastewater treatment plant serving a large metropolitan area in Massachusetts and found that the amount of SARS-CoV-2 particles in the sewage samples indicated a far higher number of people likely infected with Covid-19 than the reported cases in that area.

Researchers from biotech startup Biobot Analytics, working with a team from Massachusetts Institute of Technology, Harvard, and Brigham and Women’s Hospital, estimate there were at least 2,300 people infected with Covid-19 in the area around the treatment facility. But at the time of analysis, which has not yet been peer-reviewed, there were 446 cases officially reported in that area.It was interesting that our estimation was definitely higher than the number of confirmed cases in the area,” said Mariana Matus, CEO and co-founder of Biobot, adding that public health officials had already considered the possibility that the actual case count was much higher than what had been confirmed.

The company shared the findings with local health authorities including the Boston Public Health Commission and the Massachusetts Department of Public Health. Their response was “extremely positive,” Matus said. “They could believe that [our] numbers could be correct and not out of the realm of possibility.”