The Maine Center for Disease Control and Prevention estimates that upward of 80% of new COVID-19 cases in the state are the omicron variant, the agency’s director said Wednesday.

The explosion of new infections over the past couple of weeks is causing immense strain on Maine’s health care system. On Wednesday, 413 individuals were hospitalized with the coronavirus across the state, which broke the previous record set Monday by 10.

The number of people in noncritical care units — 307 — was also at an all-time high Wednesday.

“These peak hospitalization rates are of obvious concern, both for the human toll they take as well as the continued stress that they’ve placed on our health care systems,” Maine CDC Director Dr. Nirav Shah said at a media briefing Wednesday.

He warned against taking early reports that omicron is less severe than previous strains as any indication that the virus is slowing down in Maine.

“Even if omicron were say 10% milder than delta, it’s still 200% more contagious,” Shah said. “The sum of that impact on our population is greater than its impact on any individual.”

Omicron’s high transmissibility also makes it more difficult to isolate cases through contact tracing, prompting the Maine CDC and Department of Education to change its standard operating procedures for contact tracing in schools.

Under the new policy announced Wednesday, schools that have a universal masking requirement in place may choose to suspend contact tracing for positive cases.

Shah said omicron has “distinct biological characteristics” that lower the effectiveness of contact tracing. They include its contagiousness, the shorter period from when an individual is exposed to the virus to when they can infect others, and that “the majority of transmission” happens in the days before an individual begins to experience symptoms or the first few days after the onset of symptoms. However, the latter characteristic is not specific to omicron.

“That is to say COVID is a front-loaded virus from a transmission perspective and omicron even more so than prior variants,” Shah said. “In short, trying to catch omicron by contact tracing is like trying to catch a bullet train on a bicycle. The train is long gone from the station by the time you even get your helmet on.”

Fueling the omicron-driven bullet train is, in part, the pockets of unvaccinated individuals in communities across the state that give the virus even more room to spread.

For instance, Lewiston and Auburn have recorded 1,275 and 647 new cases, respectively, between Dec. 21 and Jan. 9, according to ZIP code data from the Maine CDC.

As of late December, there were about 24,100 Lewiston residents and more than 16,100 Auburn residents who were not fully vaccinated, one of the highest concentrations of unvaccinated individuals in the state.

About 67% of Lewiston residents and just under 70% of Auburn residents are fully vaccinated.

Providers at the region’s two largest hospitals — Central Maine Medical Center and St. Mary’s Regional Medical Center, both in Lewiston — saw more COVID patients in a single day than ever before earlier this week.

Shah said it continues to be the case across the state that about 70% of individuals hospitalized with COVID are not fully vaccinated. That rate is greater when considering those in an intensive care unit or on a ventilator.

“That’s quite a staggering figure,” Shah said Wednesday. “I mean, in my mind, there are not many things in medicine or in public health that can reduce your risk by that significant degree as can the COVID vaccines.”