Levels of COVID-19 in eastern Massachusetts wastewater have shot up in recent days, potentially indicating an upswing in cases. 

Wastewater surveillance can be an early warning sign of COVID-19’s spread, sometimes detecting shedded virus even before infected people develop symptoms, according to the Centers for Disease Control and Prevention. 

The Massachusetts Water Resources Authority tracks wastewater at the Deer Island Treatment Plant for indicators of the virus, with samples taken several times a week and analyzed by Biobot Analytics, according to the MWRA website.