What's behind the 'dire' COVID-19 surge in Michigan?

Michigan is in the midst of its fourth COVID-19 wave -- and there is no end in sight, hospital officials said.

Cases and hospitalizations are rivaling levels seen in earlier parts of the pandemic, when vaccines weren't widely available. The surge also comes at a time when non-COVID-19-related patients are being admitted, flu cases are emerging and health systems are understaffed, Brian Peters, CEO of the Michigan Health & Hospital Association, told ABC News.

Unvaccinated people continue to make up the majority of those infected with COVID-19, including severe cases of the infection. Roughly around three-quarters of COVID-19 cases, hospitalizations and deaths were in unvaccinated people from Oct. 21 to Nov. 19, according to state data.

Around 45% of the state remains unvaccinated, according to federal data.

"The situation right here in Michigan is as dire as it has ever been since the start of this pandemic," Peters said.

Michigan reported a nearly 20% positivity rate in the past week, and every county is currently at the state's highest risk level for transmission.

Michigan is not alone in seeing COVID-19 cases and hospitalizations increase due to the delta variant, especially as colder weather has approached, people have gathered indoors more and pandemic fatigue has long set in. Though the duration of this surge, and the speed with which cases have "skyrocketed" in the past three weeks, is alarming, Dr. Darryl Elmouchi, president of Spectrum Health West Michigan, which operates 14 hospitals, told ABC News.

"If you look at most other states, and all the surges we've had, usually you start at a low point and you go up really quickly, and then you come down pretty quickly," he said. "What happened for us is we went up gradually enough, but we went up high enough, with [positivity rates] in the teens, that when we shot up, we shot up from that baseline."

"This has far surpassed anything we've seen before -- both in how long it's been going on, and now its seemingly never-ending peak," he added. "We just don't know when the end will be, and we're very worried it will have a very long tail."

Michigan reported its second-highest number of COVID-19 cases and case rates in the past week, according to the state's latest weekly coronavirus report, released Tuesday. That follows records set in both cases and case rates the previous week. Hospitalized COVID-19 patients also increased 13% during the past week, the report found.

"I felt like probably the surge we had last fall was going to be the worst we've ever seen. I never would have guessed that we would be in yet another surge and that it would be the worst surge yet," Sandra Gilman, a nurse and hospital supervisor for Spectrum Health, told ABC News.

At Spectrum Health West Michigan, unvaccinated COVID-19 patients are generally about nine years younger and only have two comorbidities, as opposed to four, when compared to vaccinated patients, "meaning that they're younger and healthier when they're coming in," Elmouchi said.

"That tells us the importance of being vaccinated," he said. "And that's what's so heartbreaking for our teams, is that they see all these people that are so sick, being on the ventilator and even dying, and they know it's preventable. It's heart-wrenching."

Due to a mix of early nursing retirements, pandemic burnout and a "rising tide of violence" against health care staff, Michigan hospitals are treating the latest surge in COVID-19 patients amid a staffing shortage, according to Peters. There are approximately 875 fewer staffed hospital beds in Michigan than in November 2020, he said.

"That is incredibly concerning, because there's not a rapid or easy solution to that problem," Peters said.

Amid the staffing strain, this week, the Department of Defense temporarily deployed nearly four dozen medical personnel, including registered nurses, doctors and respiratory therapists, to two hospital systems in the state.

The help is welcome, though more is needed, Peters said, especially as the pandemic only worsened an existing health care workforce shortage. Among other measures, his organization is advocating for a $650 million special appropriation in the state legislature that would provide payments to health care staff to encourage them to stay in their jobs, as well as offer incentives for training programs to increase the number of workers in the pipeline, he said.

For now, hospital capacity remains a concern throughout the state, where every region, from urban to rural, is a "hotspot," Peters said.

At Spectrum Health West Michigan, the intensive care units are operating at 147% of their traditional capacity, Elmouchi said.

Statewide, hospitals are operating at almost 85% occupancy, according to state data.

In recent weeks, some hospitals have had to divert patients to other hospitals and delay elective procedures, Peters said.

"That doesn't necessarily create a quality-of-care problem as much as it can be a convenience problem," he said. "But what we're very fearful of, is that if these COVID numbers don't level off and decline, you're going to start seeing real access challenges, where literally there's no more capacity to care for patients, COVID or otherwise, in certain communities."

"We're doing everything we possibly can to avoid that outcome, but without the public's help, that's our future," he added.

Health officials are urging residents to get vaccinated and receive booster shots and to mask up indoors in public settings to help alleviate the surge -- especially amid concerns and questions around the transmissibility and mutations of the new omicron variant, which was first detected in the U.S. Wednesday in California.

"Ensuring that as many Michiganders as possible are vaccinated remains the best protection we have against COVID-19 -- including variants of concern," Dr. Natasha Bagdasarian, Michigan's chief medical executive, said in a statement this week.

Peters said he has been encouraged by the continued increase in vaccinations in the state, including among newly eligible pediatric populations, but "those numbers aren't growing rapidly enough."

"[Omicron] is yet another reason for the public to get vaccinated now without waiting any longer," he said. "I fear that there are so many Michiganders, and I'm sure it's true outside of Michigan as well, but who believe that the pandemic is largely over. And nothing could be further from the truth."

ABC News' Arielle Mitropoulos contributed to this report.