The city of Bangor's wastewater treatment plant on Main Street is pictured on July 28, 2014. Credit: Linda Coan O'Kresik / BDN

Maine could be in the throes of another surge of COVID-19 that official case numbers aren’t fully capturing, as concentrations of virus in wastewater have remained high throughout the state over the past week.

Several municipalities in the past week have reported their worst measurements since the state rolled out broad wastewater testing in early February, according to data from the Maine Center for Disease Control and Prevention and Biobot.

The highest wastewater concentrations in the past week again came from Aroostook County, while wastewater testing sites in central and southern Maine also reported significant jumps.

Maine’s average wastewater numbers remained far higher than the national average.

Higher concentrations of COVID-19 in wastewater are a leading indicator of virus transmission, public health officials have warned, with other indicators such as higher case numbers and hospitalizations generally coming later. Case numbers also may not suggest the full extent of COVID-19 transmission due to greater use of at-home tests whose results aren’t reported.

Maine is not alone with the rising COVID-19 levels: average virus concentrations nationwide have been ticking upward since late March, Biobot data show. But New England has generally reported among the worst wastewater numbers recently, with Maine and Vermont reporting the highest average concentrations in the U.S. in the past six weeks, according to Biobot.

Major Maine cities and towns including Augusta, Bangor, Belfast, Brunswick and Lewiston continued to report virus levels in the highest 10 percent of samples nationally in the past week.

Virus concentrations remained highest, however, in Aroostook County, with Fort Kent last week recording the greatest concentration reported by any Maine municipality through the Biobot measurements since early February, when the state began testing at most sites. The result puts Fort Kent at the top of the nation for virus concentrations in its wastewater.

Maine expanded wastewater testing a few months ago after the peak of the winter omicron surge, so the record wastewater levels do not mean overall transmission of the virus is the worst it has ever been. But it suggests the virus is continuing to spread rapidly after a more contagious strain of the omicron variant became dominant here.

Reported virus cases in Maine have also risen nearly 50 percent in the past two weeks, with the seven-day average of new cases reported by the Maine CDC rising to 309 as of Wednesday, up from 211 two weeks ago. The seven-day case rate in Aroostook County is more than twice the state average.

Importantly, hospitalizations have not yet mirrored the surge in COVID-19 transmission so far. As of Wednesday, 100 people were hospitalized with the virus in Maine. Statewide hospitalizations have fluctuated over the past month but have not shown a sustained increase or decrease.