Are you among the 1 in 5 Americans with long COVID? Here’s what you need to know about how brain-foggy—and potentially dangerous—it is
Fortune · Photo illustration by Getty Images

Maybe you know the feeling.

You dodged the initial spring 2020 wave of COVID, but caught the virus during the Delta wave of fall 2021, or the initial Omicron wave the following holidays, or another Omicron spawn more recently. Months later, you find yourself feeling a little tired and … foggy.

You could be forgiven for wondering, “Do I have long COVID? Is that why I’m mentally hazy?”

Indeed, brain fog, muscle aches, and fatigue are some of the most common symptoms of the nebulous condition called long COVID, which experts think affects as many as one in five Americans who survived the relatively new virus.

They’re seemingly mild, compared to the more than 200 other potential symptoms of long COVID, like the development or worsening of cardiac ailments, autoimmune diseases, and neurological issues like a persistent feeling of “brain on fire.”

Just how likely is it that your new, post-COVID symptoms are long COVID? How long will they last? And what’s the difference between a bout of brain fog and a potentially fatal post-COVID complication?

What’s to blame for my new health issue?

They’re the questions on the minds of countless patients and doctors right now: Is my new eczema long COVID? Is my worsening diabetic glycemic control due to COVID? I feel kind of mentally foggy—am I a “long hauler”?

It’s hard to attribute a symptom to a condition like long COVID when that condition has yet to be clearly defined, experts say.

The trouble is that—for now, at least—“long COVID” can encompass everything from patients who had mild COVID and have lingering mild symptoms, to those who were hospitalized with severe COVID and continue to suffer from resulting organ damage, Dr. Alba Miranda Azola, co-director of the Post-Acute COVID-19 Team Program at Johns Hopkins University School of Medicine, told Fortune.

For those with pre-existing conditions, it’s impossible to say if such outcomes—say, a heart attack—are due to COVID, the condition, or a combination of both—and the answer might vary by person. Those who had severe COVID-19 are at greater risk for death in the year following, according to a 2021 study out of Florida that considered more than 13,000 health records. And a study published in March of this year, considering over 150,000 COVID survivors and control groups in the thousands, found that survivors were at a substantially increased risk of heart disease, which could lead to death.

What's more, some long COVID patients have symptoms that aren’t related to the condition, or that would have occurred anyway.

When will it go away?

As far as how long “long COVID” symptoms might last, some patients do report improvement and symptoms that resolve completely in a matter of months, experts say.