A tester holds printed instructions at a mobile testing location for COVID-19, Tuesday, Dec. 8, 2020, in Auburn, Maine. Credit: Robert F. Bukaty / AP

A more contagious strain of the omicron variant is growing more prevalent in Maine after improvements in the state’s case and hospitalization numbers have largely stalled out.

The BA.2 variant — sometimes referred to as “stealth omicron” — was first identified in Maine in late February. It is estimated to be roughly 30 percent more contagious than the original omicron variant that emerged last fall, and has been cited as a major contributor to rising virus rates in much of Europe.

Estimates for the share of BA.2 infections in Maine cases sampled each day by Walgreens ranged from 26 percent to 69 percent in the past week, according to company data. That is up from between 12 percent and 20 percent of samples analyzed in the first week of March.

It reflects a national trend as the more contagious train has become dominant across the U.S. in the past few weeks, raising concerns about a spring surge in virus cases. Maine has not seen a major surge so far. Reported infection levels have remained mostly flat of late after weeks of steady decline. Hospitalizations, another indicator of COVID-19 prevalence, have likewise been relatively unchanged in the past week, although they ticked up slightly Wednesday.

The BA.2 variant accounted for roughly 55 percent of new U.S. cases last week, according to data from the U.S. Centers for Disease Control and Prevention. Regional estimates suggested it made up more like 73 percent of cases in New England, a greater share than in other parts of the U.S.

Those estimates might not reflect the situation in Maine. Transmission of the virus in northern New England states has often lagged that in Boston and the rest of the region over the course of the pandemic. The omicron variant took off later here than most of the rest of the U.S., although it now accounts for virtually all new cases here, according to state data.