COVID-19 cases have returned to southeastern Connecticut hospitals.

Both Lawrence + Memorial Hospital in New London and Backus Hospital in Norwich were treating five patients with the coronavirus disease Thursday, while Westerly Hospital had none.

One of the L+M patients was in intensive care, Dr. Oliver Mayorga, the hospital’s chief medical officer, said in an interview.

L+M admitted its first COVID-19 patient in nearly a month this past weekend.

Hartford HealthCare reported it was treating 23 COVID-19 patients across its seven-hospital system, which includes Backus. The total was up from 15 a week ago and 12 two weeks ago, according to Dr. Ajay Kumar, Hartford HealthCare’s chief clinical officer, who addressed reporters during a virtual news conference Thursday.

Five of the system’s current coronavirus patients were in intensive care, including two at Backus.

Physicians attributed the latest wave of cases to the emergence of the highly contagious delta variant, a mutated version of the virus originating in India, and the youthful vulnerability of those who have yet to be fully vaccinated.

“This is a pandemic of the unvaccinated,” Kumar said.

“I ask everybody who is not vaccinated, or is on the fence, to engage with health care providers and ask questions about the pros and cons, and hopefully make a decision that is consistent with the safety of our society, your family and yourself,” he said.

He added that the vaccine is “extraordinarily safe.”

More than 2.1 million people have been fully vaccinated in Connecticut, resulting in 854 "breakthrough" cases, including 393 with symptoms, 150 requiring hospitalization and 21 resulting in death, Kumar said, a mortality rate of 0.001%. The mortality rate among those who have not been vaccinated is 100 times higher, he said.

Mayorga said all but one of L+M’s COVID-19 patients were unvaccinated and the patient who was vaccinated had other conditions that made him especially vulnerable to the disease.

In treating COVID-19 patients, L+M is presuming that all of them have been infected with the delta variant, Mayorga said.

“It’s definitely prevalent,” he said. “We have to assume it’s part of the reason we’re seeing another wave (of the coronavirus disease). We know it’s more transmissible (than previously) and we know some routine interventions are ineffective against it.”

Treating patients with monoclonal antibodies, for example, has proven ineffective in patients with the delta variant, Mayorga said.

Both Kumar and Mayorga said most of the current COVID-19 patients in their hospitals are in their 20s, 30s and 40s, which they said was not surprising. Generally, greater percentages of older people have been vaccinated.

As of Thursday, 96% of Connecticut residents 65 and older had received at least one dose of the COVID-19 vaccine, according to Gov. Ned Lamont's office.

Mayorga said the fact that in rare cases people who have been vaccinated still get the disease shouldn’t call the vaccine’s effectiveness into question. While the vaccine doesn’t prevent the virus from getting into a person’s system, it fights the virus, providing protection against sickness and death. The vaccinated, whether they exhibit symptoms or not, can infect other people, he said.

Whether a vaccinated person should still wear a mask depends on their environment — the prevalence of the disease and the percentage of those vaccinated, Mayorga said.

“If you’re in a population where everyone is vaccinated, you don’t need to wear a mask,” he said. “But if you’re in another state, like Missouri, you should be wearing a mask even if you’re vaccinated to protect others."

“If you’re in a crowd and you don’t know how many are vaccinated, you would want to wear a mask to be safe,” he said.

Connecticut’s COVID-19 update

The governor's office reported Thursday it had counted 295 new cases of the disease since the previous day and had collected 13,270 new test results. The one-day positivity rate of 2.22% was among the highest in weeks. Hospitalizations had crept up to 66, an increase of eight.

The deaths of four Connecticut residents were linked to the disease since the previous Thursday, bringing the state’s toll since the pandemic began in March 2020 to 8,286.

b.hallenbeck@theday.com