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The Delta variant accounts for the vast majority of COVID-19 cases in the U.S. Spencer Platt/Getty Images
  • Mathematical models suggest coronavirus cases could continue to rise in the United States until mid-October. How much they rise depends on people’s behaviors.
  • The best clue to what’s in store for Americans comes from the United Kingdom, where the daily number of new infections recently fell for 7 days in a row.
  • As with the U.K., the Delta variant now predominates in the U.S., accounting for over 8 out of every 10 cases.

As coronavirus cases continue to rise sharply throughout the United States — driven by the highly infectious Delta variant — many are wondering when this surge will end.

There are plenty of mathematical models that attempt to predict the country’s pandemic future.

But for some experts, the best clue to what’s in store for Americans comes from the United Kingdom, where the daily number of new infections recently fell for 7 days in a row.

Many public health experts had predicted that cases in the U.K. would continue upward without any sign of near-term relief.

As recently as early last week, some epidemiologists were warning of a “difficult summer” ahead for the U.K., with coronavirus cases possibly reaching 100,000 or 200,000 a day, reported BBC News.

At this level, there could be as many as 2,000 hospitalizations a day, which experts said would cause a “major disruption” to the country’s National Health Service (NHS).

At the time, daily coronavirus cases in the U.K. were around 50,000.

But then the unexpected happened.

A few days after “freedom day” on July 19 — when the country lifted most remaining coronavirus restrictions after three national lockdowns and almost 130,000 deaths — the number of reported cases started to drop.

They continued falling for 7 days, until rising again for 2 days… and then falling again slightly on Friday.

Now the world is watching closely to see which way cases will head over the next few weeks, in a country with high vaccination rates — over 68 percent of people with at least one dose — and the Delta variant dominating new cases.

“Unfortunately, we will not be able to know if we are at a peak until we have passed it, probably by a few weeks,” Graham Medley, PhD, a professor at London School of Hygiene & Tropical Medicine, wrote in The Guardian.

To know if the country is really past the current peak, he says you have to look at not only cases but also COVID-19 hospitalizations, which lag about a week behind.

If both cases and hospital admissions drop, “then we will be able to say that the day with lower cases 3 weeks earlier was just after the peak, but actually the peak in infections was a week before that,” he wrote.

Medley expects that even if the current U.K. surge peaks, the country won’t see a steady decline in cases. Instead, he expects that over the next couple of months there will be many dwindling peaks in different locations, “like going over a range of hills.”

The U.K. has been a bellwether for the U.S. throughout much of the pandemic. But there are differences between the countries that make it difficult to transfer the U.K.’s Delta variant experience across the ocean.

As with the U.K., the Delta variant now predominates in the U.S., accounting for over 8 out of every 10 cases.

But the vaccination campaign in the U.S. has stalled, with only around 57.9 percent of Americans having at least one dose of a COVID-19 vaccine. Vaccination rates also vary widely throughout the country, with some counties still highly vulnerable to a Delta variant surge.

Texas is one of those at-risk areas.

“There’s enough vulnerability in our population to have a surge that meets or exceeds what we saw last summer and winter,” said Dr. Spencer Fox, associate director of the UT COVID-19 Modeling Consortium, who helped develop projections for Texas.

He says this vulnerability is due to a significant proportion of the population not having immunity to the virus — either through vaccination or natural infection — along with the presence of the Delta variant.

“We’re seeing the combined impact of all of those factors right now,” he said.

Another COVID-19 model, which looks at the entire U.S., predicts that coronavirus cases will continue to rise through the summer and fall, peaking in mid-October.

This projection was released last week by the COVID-19 Scenario Modeling Hub. It combines 10 mathematical models from various groups of researchers to create an “ensemble” projection.

The group’s latest projection looks at four scenarios based on how many Americans get vaccinated and the spread of the dominant coronavirus variant.

Justin Lessler, PhD, an epidemiologist at the University of North Carolina who helps run the modeling hub, told NPR that in the most likely scenario, vaccination will top out at around 70 percent of eligible Americans and the most dominant variant will be highly transmissible, as we’ve seen with Delta.

In this scenario, the peak of the current surge will occur in mid-October, with around 59,000 cases and around 850 deaths per day, the model shows.

This is just the middle of the range. In the worst case for this scenario, the country could see 246,000 infections and around 4,500 deaths from COVID-19 at the October peak.

Models like these have a wide range of possible outcomes because many factors can affect the spread of the coronavirus and the resulting COVID-19 hospitalizations and deaths.

But they provide a glimpse at what could happen in the near future under certain conditions and highlight which interventions can help change the course of the surge.

As the Delta variant surge continues throughout much of the U.S., there has been a renewed effort to jump-start the country’s stalled vaccination program.

Another reason to take stronger measures to control the spread of the virus is to reduce the risk that another, more dangerous, variant will arise.

“The biggest concern is that when the coronavirus is allowed to spread from person to person, there is a risk that the virus will mutate into a form that is no longer susceptible to the immune protection generated by the vaccines,” said Dr. Lewis S. Nelson, professor and chair of emergency medicine at Rutgers New Jersey Medical School.

To fight the resurgent virus, more companies are requiring that employees be vaccinated before returning to the office. President Biden also announced that all federal employees will need to be vaccinated or undergo regular testing and other mitigation measures.

Biden even called on states and localities to offer people incentives to get vaccinated, including paying them $100.

The surge itself seems to have motivated many people who had been putting off getting their first dose, with the pace of vaccinations picking up.

These are all good signs.

“We know vaccinations are going to be the most effective and safest way for us to get out of this pandemic,” said Fox.

The COVID-19 vaccines currently approved in the U.S. are highly effective against infection or symptomatic disease, although the Delta variant has eroded some of that protection.

However, the vaccines still offer strong protection against serious illness and death, which is why the vast majority of COVID-19 hospitalizations and deaths in the U.S. are now among the unvaccinated.

More vaccinations mean fewer people ending up in the hospital or dying from COVID-19. Still, it will take time to see the effects of this renewed public interest in vaccination.

“Vaccinations will not actually prevent the surge from happening, because we’re already in the midst of it,” said Fox. “It will take too long for immunity to be generated from the vaccines to prevent the surge — we’re already on the train barreling down the railway tracks.”

That’s why his group is calling for other public health measures in order to reduce the number of cases and hospitalizations in Texas.

“Our projections suggest that we will be straining healthcare capacity pretty imminently unless there’s a very strong behavioral change, where people — even those who are vaccinated — begin to take more precautions, such as wearing masks, social distancing, and avoiding nonessential and more risky activities,” said Fox.