Samples of wastewater taken from in and around Boston show levels of COVID-19 near the city at its highest point since the first week of February.

By testing for COVID in the water coming from toilets, showers and other drains across Greater Boston, authorities have tracked the spread of the pandemic without relying on local residents to take a viral test themselves.

After falling off from the height of the pandemic in January, coronavirus levels in the Boston area’s wastewater have surged significantly in recent weeks.