Earlier this year, Dr. Jeremy Faust noticed what he considered a remarkable COVID landmark that came and went with little fanfare.

From early May through early August, COVID was virtually nonexistent in Massachusetts’ waste water. During that roughly three-month period, the virus claimed fewer than 10 lives, a record low over the past six years.

“We literally had, essentially, nearly undetectable levels,” said Faust, an emergency physician at Brigham and Women’s Hospital who also researches public health. “This is, honestly, shockingly low and great.”

After that lull, COVID levels are ticking back up in Massachusetts, as they do every fall and winter. It’s a small increase, though, and emergency room visits, hospitalizations, and deaths remain at record lows. People with COVID are also clearing infections faster, Faust said.

“Honestly, when I see a COVID case I am no more alarmed than I am when I see an influenza case,” he said.

Seven years ago, virologists and epidemiologists predicted that as human immune systems became accustomed to the new virus, COVID would eventually fade into the mix of endemic respiratory illnesses. That moment is here, many experts say.

It’s possible, some experts said, that severe illness and mortality from COVID will become even less frequent over time.

While physicians differ on whether COVID is truly no more hazardous than flu, federal data show the illnesses now trigger a comparable number of deaths. The Centers for Disease Control and Prevention estimated that overall flu deaths from October 2024 to April 2025, the most recent confirmed data available, were about 45,000. COVID deaths were estimated to range from 34,000 to 53,000 from July 2024 to June 2025.

Which is to say, COVID should be taken seriously, but it’s no longer a particularly unique threat.

“You should be as scared of this virus as you’re scared of flu, which is to say scared,” said Dr. Paul Offit, one of the nation’s leading experts on vaccines and director of the Vaccine Education Center at Children’s Hospital of Philadelphia.

Offit has long dismissed the need for healthy adults to repeatedly get vaccinated if they have already received shots or have recovered from a bout of COVID. The exceptions, he said, are those vulnerable to serious outcomes from COVID infections: seniors, pregnant women, people with some chronic medical conditions, and the immunocompromised.

The state Department of Public Health still recommends annual vaccination for adults as well as high-risk groups. Booster shots are optional for healthy, previously vaccinated children ages two to 18.

The normalization of COVID is as much psychological as a consequence of immunity, and testing for COVID is increasingly a rarity, said Dr. Catherine Brown, the state epidemiologist.

Positive COVID tests can help determine the course of treatment, which could make the difference between moderate symptoms and severe illness, experts said. For people with immunity, though, the need for specialized treatments has become less common. Recent studies of older or high-risk patients who had been vaccinated found no evidence that Paxlovid, an antiviral treatment, reduced hospitalizations or deaths. Rates of both were already low even among vulnerable populations, one New England Journal of Medicine paper from April noted. That paper did find some evidence the drug may help patients recover faster.

Those caring for vulnerable patients or family members should still test and isolate if they are ill, experts said.

One expert who still tests himself is Michael Osterholm, founder of the Center for Infectious Disease Research and Policy at the University of Minnesota, though he does it more for his own edification than anything else.

“It’s my own curiosity of what’s happening with infection,” said Osterholm, an epidemiologist in his 70s. “I do the same thing with flu.”

None of the experts ruled out the possibility of a new COVID variant that could significantly evade existing immune protections to cause another major health emergency. But most national experts said such a development is unlikely.

“I don’t imagine a 2020 in our future again with this particular virus,” said Jennifer Nuzzo, director of the Pandemic Center at the Brown University School of Public Health. “I personally haven’t seen evidence that makes me worried we’re going to have some wild new variant that’s going to upend society.”

While opinions vary on COVID’s future, experts are virtually unanimous in saying that another major health threat from a different novel virus is almost a certainty.

“I’m quite convinced we’re going to see additional new coronaviruses show up,” Osterholm said.

The reason, Offit, the Philadelphia vaccinologist, said, is humans’ proximity to bats.

Bats are a common reservoir for coronaviruses, which have in some cases mutated to infect humans. COVID-19 is just one condition caused by a type of SARS coronavirus and is not the most virulent. One SARS virus that spread from 2002 to 2003 killed about 10 percent of the people infected. The mortality rate for MERS, another coronavirus, could be as high as 37 percent, according to the World Health Organization.

If one of those illnesses adapted to transmit as easily as COVID-19, Osterholm said, the results could be devastating.

One expert, however, said people’s immunity to COVID may offer some protection against other SARS viruses.

“I think it would be enough so we wouldn’t get a pandemic,” said Dr. Stanley Perlman, a professor of microbiology and immunology at the University of Iowa.

Faust, like others, didn’t rule out the possibility that COVID could again become a serious threat. It has surprised him before.

He recalled seeing his first three COVID patients more than six years ago and realizing COVID would cause a massive health emergency. This year, he said, the virus shocked him again.

“It was worse for longer than I thought it was going to be, but it got better faster than I ever thought it could,” he said.

Jason Laughlin can be reached at jason.laughlin@globe.com. Follow him @jasmlaughlin.