Coronavirus levels in the Boston region’s wastewater continued to fall Friday, according to state data reported Sunday, but public health officials cautioned that COVID-19 remained a threat amid a nationwide surge in cases and hospitalizations.

The latest figures from the region’s wastewater data, seen by experts as an early warning system on the virus’s progress locally, came amid grim national news about the pandemic.

The nation continues to grapple with soaring new cases daily — passing more than 800,000 as of Sunday with the spread of the highly infectious Omicron variant — while hospitals are stressed caring for a surge in patients.