In this April 28, 2020, file photo, Dr. Nirav Shah, director of the Maine Center for Disease Control and Prevention, speaks at a news conference in Augusta. Credit: Robert F. Bukaty / AP

AUGUSTA, Maine – Maine reported a record 18 percent of COVID-19 tests coming back positive in the past week, which state health officials attribute at least in part to the spread of the more contagious omicron variant.

The rising positivity rate reflects more people contracting the virus rather than a decline in testing, Maine Center for Disease Control and Prevention Director Nirav Shah said Wednesday. Maine saw testing numbers contract over the holidays, but they have largely rebounded.

The positivity rate, or the percentage of tests coming back positive, dipped below 1 percent at some points during the pandemic in Maine when case levels were much lower. Epidemiologists use the figure in concert with case counts to assess spread. It is based on only tests reported to the state, and does not include results from at-home tests.

The more contagious omicron variant may be the main driver of rising cases in Maine, as it continues to make up a greater proportion of transmission across the U.S. An analysis in late December found just 8 percent of positive samples tested for variants in Maine were omicron. But that number is likely a “dramatic undercount,” Shah said, citing internal data the Maine CDC has received from laboratories in the last few days.

“The prevalence of omicron is certainly much greater,” Shah said.