Pandemic versus endemic: What to know about the next Covid-19 chapter

Remember when the pandemic was “over?” This halcyon moment of 2021 happened during what seemed a particularly sunny June. Having struggled through the anxiety of vaccine availability for months, suddenly any adult could get a jab, and once fully vaccinated, we could even discard our masks and breathe easy. The Dave Matthews Band was embarking on a summer tour and Black Widow finally had a release date. The class of 2025 would spend freshman year inside the schoolhouse.

The idea that we might be “done” with Covid-19 did not last. By late July, the Delta variant had spread throughout the U.S., fueled by stagnant vaccination rates. New Covid-19 cases in the U.S. ballooned from about 12,000 a day at the start of July to 160,000 by the start of September, numbers not seen since before vaccination. Masks came back and so did the anxiety — with a vengeance.

So, when will we be done with Covid-19? Likely never. Experts say Covid-19 will evolve from a pandemic to an endemic disease — in other words, it will become a common disease, like the cold or flu, spreading and mutating at a slower rate, but ultimately without an end. The thing is: We still don’t know when that switch will happen. But there are certain factors that could help tip the scale.

What’s the difference between “pandemic” and “endemic?”

The designation “pandemic” is given to a disease outbreak that spreads rapidly across multiple countries and continents and that typically affects a significant percentage of the population in an acute way. Covid-19 was declared a global pandemic by the World Health Organization on March 11, 2020.

The designation “endemic” is given to a disease that commonly occurs among a population. The most recognizable endemic condition is perhaps the flu, but chickenpox is another endemic disease that is almost considered a rite of passage.

Technically, there is no scientific measure separating a pandemic from an endemic disease — both pandemic and endemic diseases can be extremely transmissible, severe, or affect some kinds of people more than others, like chickenpox and children. Rather, people largely decide when a pandemic is over based on their collective perception of the threat level posed by the disease at hand, Yonatan Grad, an associate professor of immunology and infectious diseases at Harvard University, tells Inverse.

Several pandemics have transitioned to endemic status. Among them are “yellow fever and some might say HIV/AIDS in some areas of the world,” Zandrea Ambrose, a virologist at the University of Pittsburgh, tells Inverse. “An example of a bacterial pandemic that is endemic would be cholera.”

She adds that H1N1 — swine flu — is also now endemic. The disease, once a pandemic, now lays low in populations and resurfaces every few years in the form of regional outbreaks — but it doesn’t go global. Covid-19 could make the same switch as time passes and we become more inured to the disease.

For Covid-19, the endemic stage might start when societies no longer consider mitigation measures like mask requirements and vaccine mandates, says Grad. Interestingly, the UK may already be on this trajectory, as it has high caseloads but no plans to bring back strong mitigation measures beyond vaccines and masks in certain places.

“As levels of hospitalization and death go down, people will tolerate this disease,” Grad says. “At a point, we will say this is acceptable.”

“The virus will be endemic and join the continuum of all the other respiratory diseases we deal with,” he adds.

What happens when Covid-19 is endemic?

It’s hard to say how endemic Covid-19 would affect everyday life. In part, this is because there has not been a pandemic as severe and all-engulfing in a century — the last time we faced this kind of global threat was the Spanish Flu in 1918.

There could be “Covid seasons” like flu seasons when nasty strains of the virus roll through both unvaccinated and vaccinated people at certain times of the year due to seasonal factors.

“Winters will likely be worse,” Ambrose says. “We will be asked to get boosters like we get for flu. I imagine seeing masks in public will remain common, especially in winter months.”

Ultimately, Covid-19 will lose its ferocity. Populations will slowly edge toward herd immunity — another much-longed-for point in the pandemic — as more individuals get vaccinated or develop protective antibodies as a result of infection meaning there will be fewer bodies the virus can easily infect, evolve within, and then spread from to others.

There are plenty of potential catastrophes on the way, Grad says.

“It depends on what we do with vaccination and with boosters. It depends on new variants. There are still a number of unknowns that will factor into this process,” Grad says.

Covid-19 may become more of a problem in certain places due to the stark divide in some countries’ infection rates, Grad says. Some regions have enviable Covid-19 rates because of their isolation — Tonga saw its first confirmed infection in October 2021. Other island nations, like Iceland and New Zealand, have also had very few cases, as have sparsely populated countries, like Bhutan and Turkmenistan.

But as people in these regions have increasingly frequent encounters with visitors from global Covid-19 hotspots, like India, Brazil, or the United States, they may become increasingly at risk of an outbreak. That’s especially true in populations that have not reached herd immunity or had access or prior need for a wide rollout of the vaccine. This could mean some bumps along the way to a new normal of living with Covid-19.

But virologists are already starting to turn their focus on the next pandemic. Covid-19 is the latest in a string of deadly and unpredictable diseases to jump from animals to human beings through a process called zoonosis (H1N1, SARS, mad cow disease, HIV/AIDS are some of the others, to name a few).

“I think it is now recognized that coronaviruses, and other viruses, can be transmitted to humans from animals,” Ambrose says.

“There will be other flus and coronaviruses transmitted to people from animals in the future. It is a given.”