We don’t know much about “long COVID,” an umbrella term for a series of symptoms that remain for weeks, even months, after a diagnosis of COVID-19.

But what we do know is concerning enough – an alarm that we will be dealing with the physical effects of the novel coronavirus after the pandemic fades. For the sake of millions of Americans, we have to be ready.

Long COVID can mean a number of different things. Sometimes, it’s the persistence of fatigue, coughing and lack of smell well after the virus should have cleared, similar to the aftereffects of other respiratory infections.

Or, in more serious cases, it’s the effects of scarring on the lungs caused by the body’s response to the virus, such as with a Lewiston woman who spent weeks on a ventilator because of COVID-19, and months later must still use supplementary oxygen to get by.

Others experience symptoms more like post-infection syndromes such as Epstein-Barr or chronic fatigue. These folks describe ongoing pain, severe fatigue, “brain fog,” heart palpitations and gastrointestinal distress.

In it’s harshest forms, long COVID is flooring people, leaving them to wonder if their old self is ever coming back.

“I’m nowhere near the person I was a year and a half ago,” an Orland woman who has suffered from dizziness and a racing heartbeat since contracting COVID early last year told the Press Herald.

And because long COVID is most often seen following mild cases of COVID-19, and could affect a lot of people, it should change how people view the virus.

A Westbrook woman, a healthy mother of 2 whose symptoms have now lasted for 16 months, gave this warning: “You’re not just weighing the risks of getting a bad flu. You are taking a gamble that could really affect your quality of life.

Just how many people will get long COVID is unknown – estimates range from as low as 2% to up to nearly half of everyone who is infected by the virus.

Even at the low end of the range, that’s a lot of people. Just 10% of the known cases in Maine is more than 7,000 people; nationwide, it’s more than 3 million now, with tens of thousands of cases added every day.

And that’s just known cases; the U.S. Centers for Disease Control and Prevention estimates that about 114 million Americans have been infected.

Long COVID is still a mystery. Hospitals across the country, including those in Maine, are dedicating resources to researching the slate of symptoms, and doctors are just figuring out how to treat them.

There’s evidence that vaccines help relieve symptoms, possibly by showing the body how to fight them off. It’s still unclear how long COVID relates to children, a concern as more and more kids are being infected by the delta variant as schools begin to reopen.

Researchers will continue to learn more about long COVID and how to treat it.

Governments must prepare to deal with the fallout, too, as perhaps millions of Americans may need to alter their home and work lives in response to ongoing symptoms.

The rest of us can do what we can to slow the spread of the virus: Get vaccinated, and wear a mask where appropriate. Keep kids safe.

And above all, show compassion for those who sometime in the last 17 months came down with a virus – and now feels like they may never be the same.