The highly contagious Delta variant has officially arrived on Martha’s Vineyard, hospital officials confirmed Wednesday morning, as Covid-19 cases jump upward across the Cape and Islands and health experts express renewed caution during the busy summer months.

At an impromptu press briefing, hospital officials said two positive Covid-19 test samples were sequenced by the state epidemiology lab for the Delta variant, with results arriving late Tuesday night.

In a follow-up email Thursday, hospital spokesman Marissa Lefebvre said that two additional Covid-19 samples had been positively sequenced for the Delta variant. She all four samples came from vaccinated individuals.

"To date, four results have been positive for the Delta variant," Ms. Lefebvre wrote. "All four samples came from individuals who were fully vaccinated and showing mild symptoms."

A more contagious strain of the virus that originated in India in December 2020, the Delta variant quickly spread across the globe and is now estimated by the Centers for Disease Control to account for more than 80 per cent of virus cases in the United States.

The B.1 variant originally sequenced in Great Britain has also previously been detected on Martha’s Vineyard.

“The Delta variant, the one which is known to easily spread, is here on Martha’s Vineyard,” hospital president and CEO Denise Schepici said, adding: “If you’ve not been vaccinated, now’s the time to do so, and just don’t hesitate. The Delta variant is nothing to take lightly. It spreads very easily from human to human, and very quickly.”

Although the virus can still spread among vaccinated people, vaccines have been shown to significantly reduce the risk of hospitalization or serious illness, with hospital officials encouraging unvaccinated residents to get the shots.

After weeks of decline and flat-lining case rates, the Island reported 16 new positive test results between July 11 and July 17. Five additional new positive cases were reported on Tuesday.

At least six of those cases are among vaccinated residents, and almost all the patients are symptomatic, health agents and hospital officials said.

Stopping short of recommending new mask or social distancing measures, Ms. Schepici urged residents to act cautiously and encouraged mask wearing indoors as the country experiences what she called a “fourth surge.”

“I would encourage anyone that feels uncomfortable in an indoor setting to wear a mask if they can’t socially distance. I do it as a personal preference, and I urge everyone to take those precautions,” Ms. Schepici said.

She said the hospital postponed its first in-person board meeting, which was scheduled to be held this week, after the case increase — deciding to meet over Zoom instead. But she did not feel a new mask mandate was necessary in light of the case uptick.

“People have to govern themselves according to their own feelings about safety,” Ms. Schepici said. “My personal advice is, if you can’t be safely away in a certain distance in any public setting, you should wear a mask. And it’s really the density, as well as the mask wearing.”

Despite the majority of Island cases showing symptoms, hospital officials said they have had no Covid-19 hospitalizations or transfers in recent weeks. Chief nurse and head of hospital operations Claire Seguin described patient symptoms as “mild to moderate,” but not rising to the level of hospitalization.

“I think that speaks to the vaccines efficacy, because the science does show it prevents more hospitalizations,” Ms. Schepici said. “Every day I look at that number and I go, ‘amazing, amazing, amazing,’ because with the uptick, you would think we’d be having hospitalizations and . . . that’s not what we’re seeing.”

But the rise in cases comes at a busy time for the hospital and Island. Ms. Seguin said there had been a significant increase in emergency room visits this June and July compared to 2019 and 2020. She estimated approximately 600 more visits, with about 20 per cent of those cases admitted to the hospital for treatment.

“We definitely saw more patients through the month of June than we did in the prior two years,” Ms. Seguin said. “And also tracking higher for this month.”

Cape Cod has also been identified by the state as a Covid-19 hotspot, with a case cluster traced to Provincetown and cases spreading in a Yarmouth nursing home, according to a report in the Boston Globe.

With the dramatic population increase and rise in other hospital cases, Ms. Schepici continued to hammer home caution and vaccinations — as she has since the vaccine first became available in January.

Free asymptomatic Covid-19 testing remains available at TestMV, now located at the West Tisbury School, Monday through Friday from 9 a.m. to 1 p.m. The hospital provides tests for symptomatic patients, with appointments available through the call center.

Vaccine clinics remain ongoing at the hospital on Tuesdays and Fridays, relocated to the hospital Covid-19 testing drive-through tent. Islanders can schedule appointments by calling 508-684-4500.

“Thoughtful concern . . . that’s my advice,” Ms. Schepici said. “And get vaccinated, if you haven’t yet.”