The delta variant surging through the United States could peak later this month, but experts say projections are difficult and much will depend on an unpredictable factor: human behavior.

The U.S. is expected to endure a rough next few weeks no matter what.

The seven-day average for COVID-19 has risen in recent weeks to 85,866 cases per day as of Monday, the highest point since Valentine’s Day, according to data from The New York Times.

The boost in cases is higher than last summer’s peak of almost 67,000 cases but much lower than the winter highpoint of nearly 260,000 cases.

A lot of what happens in the next few weeks will depend on the population, which Nicholas Reich, an associate professor of biostatistics at the University of Massachusetts Amherst, noted is “really hard to predict and really hard to control.”

“This is the sliver of optimism that we have is that the reason it’s hard to predict is because it’s sort of in our control as a society to change the trajectory,” he said. “But it requires everybody being careful and being vigilant and looking out for each other.”

The U.S. in general has followed the United Kingdom in case trends with both the alpha and delta variants of the coronavirus. After skyrocketing cases in June and July, the U.K.’s case count has dropped dramatically, almost halving since its peak in late July.

Experts said the current U.K. trend shows that a sudden downturn in cases is possible in the U.S., but they said they are not confident the same will happen, citing different infection, vaccination and precaution compliance rates. 

Spencer Fox, the associate director of the UT COVID-19 Modeling Consortium at the University of Texas, said he doesn’t think such a decline is coming in Texas, saying the state is in “the midst of a pretty alarming surge” with “no signs of slowing.”

One in three cases documented in the U.S. last week were confirmed in Florida and Texas, White House coronavirus response coordinator Jeff ZientsJeff ZientsBiden rebukes GOP governors for barring mask mandates Overnight Health Care: Average daily COVID infections topped last summer’s peak, CDC says | US reaches 70 percent vaccination goal a month after Biden’s target | White House says CDC can’t renew eviction ban Average daily COVID-19 infections topped last summer’s peak, CDC says MORE said on Monday, as both states struggle with overwhelmed hospitals. 

“I am not very optimistic that this surge is just gonna happen to turn around anytime soon,” Fox said. “What we’re seeing is a major surge. It’s going to take a major behavioral change to slow transmission.” 

The delta variant has spread so quickly it appears to have almost spooked some who have worked on modeling projections.

Justin Lessler, an infectious disease epidemiologist at the University of North Carolina Gillings School of Global Public Health, said so far the contagious variant has increased faster than any of their models, calling it “a little bit scary.”

“Given the rate is going up, it’s either going to peak earlier than we anticipated or peak much, much higher than we anticipated,” Lessler said. “I think probably both are going to be true.”

Many Americans have quit wearing masks, and travel is at a peak since the pandemic took grip of the country last March.

Combined with the contagious delta strain, the Institute for Health Metrics and Evaluation (IHME) at the University of Washington Medicine said cases could increase until about the middle of August.

Total fatalities are estimated to reach more than 683,000 by Nov. 1, with an additional 76,000 deaths occurring between July 26 and then, under the IHME estimate.

But if the U.S. obtained 95 percent universal mask wearing, about 49,000 of those lives could be saved, said Ali Mokdad, an epidemiologist and chief strategy officer for population health

at the University of Washington. 

The CDC updated its mask guidance last week for fully vaccinated people to wear masks in indoor public settings in high-risk areas – which currently applies to 80 percent of all U.S. counties. But the announcement has sparked backlash, including among Republican lawmakers, indicating it may not have a high compliance rate. 

Some experts, including Mokdad, said hospitalizations are a better indicator for trends in the pandemic than case counts, since cases could be going undetected due to a lack of or a mild case of symptoms. Hospitalizations have also been on the rise, reaching a seven-day average of nearly 49,500 per day as of Saturday. 

In IHME’s projection, 30 states are expected to have high or extreme stress on hospital capacity and 35 states are estimated to have that level of stress on intensive care unit capacity.

“That’s a dangerous sign,” Mokdad said “You should dial back with mandates. You just ask people to stay at home if they can stay at home. And that’s what we are seeing, unfortunately, in many states right now.”

Former Food and Drug Administration Commissioner Scott Gottlieb predicted last week that the U.S. could make it through the worst of the delta variant in a matter of weeks, saying he thinks the strain has spread beyond what officials have tracked. 

“I think we’re further into this delta wave than we’re picking up,” he told CNBC. “I think in another two or three weeks we’ll be through this.” 

Other experts suggest school reopenings later this month could prolong the peak.

Such openings provide “another opportunity for a resurgence to occur,” Andrew Pekosz, a professor of molecular microbiology and immunology at the Johns Hopkins Bloomberg School of Public Health, said last week. 

Jeffrey Shaman, a professor of environmental health at the Columbia University’s Mailman School of Public Health, aligned with Gottlieb with a cautious projection that cases could peak in about two to four weeks, followed by hospitalizations. 

But Shaman emphasized that such projections are clouded in uncertainty since they make assumptions about the future that depend on unpredictable human behavior, including whether officials will implement new precautionary measures in the coming weeks. 

“The reality is … I don’t think anybody knows what the policy changes and individual practices are going to be, how closely they’re going to be adhered to,” he said.

In a scenario assuming no changes in behavior, Shaman said the U.S.’s case rate could peak at slightly less than 150,000 cases per day, with 1 million cases recorded per week.