Yale researchers say a spike in COVID-19 cases may be coming to Stamford, Bridgeport and New Haven - and they say the evidence is in the cities' sewers.

Researchers at Yale say trace amounts of COVID-19 found in Stamford's wastewater mean there could be more cases coming over the next few days.

Yale's COVID-19 Tracker says the amount of viral RNA found in waste from the city's sewers Wednesday was more than twice the previous record.

Researchers found similar spikes over the past few days in Bridgeport and New Haven. In the past, more viral traces in feces has predicted a rise in cases.

Mayor David Martin says he sent an alert to residents Wednesday night about the virus spreading in the city.

Martin says Stamford will roll back to phase two.