On May 8, 1945, when World War II ended in Europe, flags were unfurled, bonfires were lit, and people packed the pubs. In Britain, a national holiday marked the end of terrible violence that left cities destroyed and millions dead.

For more than a year, the world has been at war with the vicious, silently spreading coronavirus, which has killed nearly 4 million of us and counting. But this enemy won't sign an official surrender. In fact, we may never defeat it.

Though COVID-19 cases and deaths have declined dramatically from their peak in many areas, there's little consensus about what that threshold means.

Viral pandemics don't have an "on/off" switch. Lacking a formal announcement of its end, the pandemic will be "over" when it's over for you.

For those who have denied the coronavirus' threat, the pandemic was over before it started. Meanwhile, for those who are immunosuppressed, (some 12 million people in the U.S. alone) or for those who lost loved ones, there's no end in sight.

"I don't think people are prepared for how arbitrary the ending is," said Steven Taylor, author of "The Psychology of Pandemics" and a professor and clinical psychologist at Canada's University of British Columbia. "Some people think, 'Oh I'll wake up one day the sun will be shining and Dr. Tedros [Adhanom Ghebreyesus] from the World Health Organization is going to announce, "COVID is gone." ' That's not going to be the case."

Historically, determining a pandemic's end has been "messy," as the threat varies from country to country. "Even within countries, it will end at different rates," Taylor predicted. "And for psychological reasons, for some people the pandemic will never end."

Deciding when things are back to normal is more about emotions than numbers. We'll likely emerge from this collective crisis individually, each of us determining when the threat has faded from imminent crisis to acceptable risk.

Across much of the U.S., COVID no longer feels like the crisis it did months ago, when hot-spot hospitals filled and morgues were overwhelmed. The daily case average has returned to levels not seen since March 2020.

In Minnesota, Gov. Tim Walz ended capacity and distancing restrictions and the state's mask mandate last month. In-person work and activities have resumed. COVID is no longer front-page news.

But one's view of the pandemic is relative to where you are standing, said epidemiologist Mike Osterholm, director of the University of Minnesota's Center for Infectious Disease Research and Policy (CIDRAP).

Though nearly half of all Americans are now fully vaccinated, rates are far from uniform — some counties in the South have rates under 20%.

"Your head's in the freezer, your feet are in the oven, and your average temperature's just right," Osterholm said, explaining the "two Americas" reflected by community-level data. He expects we could see a moderate resurgence of cases in regions with low vaccination rates.

On a global level, the differences are even wider. As some Americans anticipate the pandemic's end, other countries are seeing their biggest spikes yet. The number of worldwide daily cases reached its highest point in April.

"Some people think this is just gone now, that this is it," Osterholm said. "And it's not. Globally, these have been the worst few months of the pandemic."

The more transmission continues, the more likely that new, more nefarious variants evolve, Osterholm explained. "The variants have just continued to throw curveball after curveball," he said. "I liken it to having a curveball, a spitball, a forkball and a fastball all in the same pitch."

His latest concern is the Delta variant, which appears to be both more transmissible and more capable of causing more serious illness. "It kind of becomes the top of the virus food chain wherever it hits," Osterholm said.

So far, fully vaccinated people have maintained strong protection against the variants. But those with only a single dose are faring worse against Delta than other variants so far. If a variant that can cause serious illness in fully vaccinated people emerges overseas, it would eventually come to the U.S. and neutralize the progress we've made, Osterholm said.

To understand the pandemic's long-term trajectory, the number to watch, he stressed, is the global vaccination rate. He noted that in low- and middle-income countries, where some 6.4 billion people live, less than one half of 1% have had access to COVID-19 vaccines so far.

"I look forward to it being done," Osterholm said of the pandemic. "I just know we have a long way to go."

Scientists generally agree that the coronavirus will eventually become a routine virus, similar to the flu.

Even when a threat is largely eliminated, it will take time for some of us to feel safe, said Ryan Van Wyk, a clinical psychologist with North Memorial Health and founder of the MN Trauma Project.

"The nervous system doesn't calibrate just based on information," he said. "We don't think our way to safety. We have experiences in which we feel safe, and then that begins to help our system to recalibrate and accept that as a new normal."

But many people, Taylor said, will be vulnerable to post-pandemic emotional problems. He's particularly concerned that those who lost close loved ones to COVID-19 will experience prolonged grief.

Taylor also is concerned about the mental well-being of those who survived a serious bout with COVID-19, pointing to a recent JAMA study that suggested 30% of people who were hospitalized with the disease developed post-traumatic stress disorder.

Even though most people are largely resilient, Taylor's recent research found that those with a previous history of emotional problems (such as a mood or anxiety disorder, obsessive-compulsive disorder, or an inability to tolerate uncertainty) experienced great distress during the pandemic and will likely continue to struggle.

"Most people will bounce back, and the people who are scarred and have problems are going to ask themselves, 'What's wrong with me?' " he said. "My concern is that could create a sense of alienation for the people for whom the pandemic hasn't ended."

As we move into a new phase of the pandemic, Taylor advises people to think of the marathon metaphor and take it day by day. .

Van Wyk suggests people acclimate at their own pace and respect others' boundaries as we slowly stretch beyond our COVID comfort zones.

"We can only move as fast as our as our nervous system feels safe, and that will look different for each person," he said.