While the rest of the country sees a slight dip in COVID-19 cases, the viral disease is running rampant in New Hampshire and Vermont, with both states seeing their highest case rates to date.

Why? The reasons vary, from the cold New England weather driving more indoor gatherings to the states’ stalled vaccination rates.

Regardless, health experts warn that if cases continue to rise, both states will head into yet another surge.

“That’s the worry. That’s what keeps a lot of us awake at night,” said Dr. Aalok Khole, an infectious disease physician at Cheshire Medical Center in Keene. “Last winter, we prepped for it, we continue prepping for it, but what’s different is we had way [stricter] mandates in place last time.”

In the week ending Thursday, the seven-day average of new COVID-19 cases in New Hampshire reached an all-time high of 880, according to data from the state’s health department. The second highest to date was back in December 2020, when New Hampshire was averaging 868 new cases per day.

In Vermont, the seven-day average for the week ending Thursday was 352 new cases, slightly down from its peak of 369 the week prior, according to data from the Vermont Department of Health. It’s next highest spike — aside from elevated numbers throughout the fall — was in April, with an average of 184 new cases per day.

Hospitalizations are also spiking, with 327 COVID-19 patients in New Hampshire hospitals and 62 in Vermont as of Wednesday and Thursday, respectively, according to data from each state’s health department.

On Friday, 340 COVID patients were in hospitals in the Granite State, according to the N.H. Hospital Association.

“The healthcare system is extremely strained treating both patients with COVID-19 and those without COVID-19 who may have delayed care or preventive screenings resulting in much more serious medical conditions,” association President Steve Ahnen said in a prepared statement. “Our hospitals are struggling to find intensive care beds and have been forced to look across state lines to transfer patients due to lack of bed capacity, while combatting the current workforce challenges that are only exacerbating the situation.”

New Hampshire hospitals had about 330 patients at the state’s peak last winter. Vermont’s also close to its highest number of hospitalizations, which it saw in February with 65 confirmed.

One of the biggest drivers of these high numbers is the weather, health experts said. The winter brings several holidays along with it, leading to more indoor gatherings and more traveling.

“Once you have ventilation affected, large gatherings — largely with unmasked individuals — it really promotes transmission, especially with delta,” Khole said. “It’s a recipe for disaster.”

Vaccination rates in both states have also largely flatlined since this summer.

As of Thursday, about 74 percent of Vermonters and 55 percent of Granite Staters were fully vaccinated.

Vermont Epidemiologist Patsy Kelso said she hopes 5- to 11-year-olds’ new eligibility for the Pfizer-BioNTech vaccine will help boost that rate and “that’s when we’ll see cases go down.”

But Khole said most of the patients with COVID that he’s seeing in Cheshire Medical’s ICU are unvaccinated, even though they are eligible for the shot.

“The age groups getting sick enough to be in the ICU and age groups passing away, that graph has shifted,” he said. “It’s no more the 75-plus and 80-plus, it’s more in the 40s, 50s and 60s. We’ve also had deaths of people in their 30s.”

Khole and Kelso stressed that the vaccine is the best way to prevent contracting and spreading the disease, and that the rise in cases does not mean the shots aren’t working.

Breakthrough cases can and do happen, but those who contract COVID-19 after vaccination are far less likely to develop severe complications from the disease or to die from it, according to the Centers for Disease Control and Prevention.

And Vermont’s case rates among those who’ve received their booster shot — an additional dose given after the protection provided by the original shots begins to wane — have actually remained steady, according to Kelso.

“What we’ve seen in our Vermont data is the group that [has received a booster shot], the case rates are not increasing,” she said, “so we are trying to encourage Vermonters to get their vaccines and their boosters when it’s their time.”

Khole added that keeping safety protocols in place — such as donning a face mask, staying home when sick and practicing proper hand hygiene — is essential when case counts are this high, especially for those who aren’t vaccinated.

“The risk is really high of them contracting the virus and then getting sick from it ...,” he said. “That’s something we’ve been talking about right from the start. It’s a stark reality we need to understand.”

Olivia Belanger can be reached at 352-1234, extension 1439, or Follow her on Twitter @OBelangerKS.