Over the last two years, new Covid cases and deaths have risen and fallen alongside surges of variants and subvariants. One constant, experts say: a continual increase in long Covid cases.

The term "long Covid" refers to the wide range of new, ongoing or returning health conditions that can affect people weeks or months after they've recovered from a Covid infection. Common symptoms include fatigue, difficulty breathing, heart palpitations, brain fog, lightheadedness, stomach pain and altered sense of taste or smell, the Centers for Disease Control says.

"There's definitely no slowing down in the demand and the need for long Covid care. It's continuing to increase," says Dr. Jason Maley, director of Boston-based Beth Israel Deaconess Medical Center's long Covid clinic, which is part of a multicenter study funded by the National Institutes of Health.

Long Covid is estimated to have affected as many as 23 million Americans as of March, according to the U.S. Government Accountability Office. Part of the problem is that its symptoms can vary from person to person, making it difficult for experts to understand — and hard for physicians to diagnose.

"There's still a lot of lack of knowledge and familiarity with long Covid, even within the medical community," Maley says.

To help you navigate those unknowns, CNBC Make It spoke with a series of long Covid experts about what to look out for, whether you're at risk and what tools might be able to help:

How do you know if you have long Covid?

If you test positive for Covid, Maley says, consider doing a self-check-in about a month after you've recovered. "Look out for common symptoms like changes in [your] thinking, memory and [your] ability to perform at work or to function effectively at home," he says.

Some of long Covid's symptoms may not seem obviously connected to the condition, at first. Take fatigue, for example: Maley says a delayed tiredness episode, even days after strenuous activity, can be a sign of long Covid.

"You may not feel exhausted when you're being active in the moment, but hours or even one to two days later, you may be hit with overwhelming exhaustion," he says.

According to the CDC, people with "more severe Covid-19 illnesses" and "underlying health conditions prior to Covid-19" may have a higher risk of developing long Covid symptoms. So, that self-check-in could be particularly important for anyone who was hospitalized with Covid, or needed intensive care to recover.

But everyone should stay vigilant: Research published in the scientific journal Pathogens in November 2021 indicates that a small portion of people with long Covid were asymptomatic, and didn't even know they had Covid in the first place.

What should you do if you have long Covid?

Everyone's experience with long Covid is a little bit different, says Dr. Thomas Gut, an associate chair of medicine and director of ambulatory care services at Staten Island University Hospital. He says symptoms can last anywhere between three and six months. Other studies show that symptoms can last for at least a year.

There aren't currently any comprehensive treatments for long Covid patients, but experts say a few at-home strategies may prove useful. For instance, if you're experiencing a lot of fatigue after recovering from Covid, try identifying the activities triggering your severe exhaustion and intentionally avoiding them for a little while.

"It's called pacing," Maley explains.

Pacing also involves adjusting your daily schedule to include built-in rest periods, for both your mind and your body, to prevent "severe" crashes. Avoiding those exhaustion episodes can help you recover more effectively from long Covid, Maley adds.

Maley also says his patients who suffer from shortness of breath often find yoga-based breathing exercises helpful — long, slow deep breaths in and out through your nose. He says some breathing exercises help strengthen your breathing muscles, while others help with breath control and the sensations of breathing.

Typically, long Covid patients don't have any lung function damage, Maley says: "We think [the shortness of breath] may relate to the muscles and nerves that control the breathing, rather than injury within the lung like a scar or something leftover from the infection."

Does being vaccinated help prevent long Covid?

The CDC notes that unvaccinated people may run a higher risk of developing long Covid post-infection. Maley says most studies so far have been "a little mixed in terms of how strong of a protection that may provide."

Dr. Nisha Viswanathan, co-director of the UCLA Health COVID-19 ambulatory monitoring program and Long COVID program, agrees. "We know that from our early studies that about one in three who [were] unvaccinated were exhibiting signs of long Covid," she says. But now, with a mixed population of vaccinated and unvaccinated people, researchers are seeking more clarity on who's still experiencing long-term symptoms.

Covid vaccines can lessen the severity of illness for people who become infected with the virus. Similarly, Maley says, multiple studies suggest that vaccinated people who develop long Covid display less severe symptoms than unvaccinated people with long Covid.

But, he adds, he can't guarantee that being vaccinated would completely protect anyone against long Covid — at least, not without further research.

Who's most at risk?

Gut notes that the Covid virus' recent mutations are causing increasingly milder infections — and since milder infections seem to cause fewer long Covid cases, he doesn't expect the next wave to create a long Covid surge.

Still, Maley says, he's currently seeing patients of all age groups with long Covid symptoms, most predominantly in young adults. Some studies also suggest long Covid is affecting women more than men.

The reason for that, Maley says, is not yet known.

Viswanathan says most of her long Covid patients already had pre-existing conditions like cardiovascular disease, high cholesterol and obesity. "So, ways to help prevent [long Covid], in addition to vaccination, really do consist of cleaner eating [and] regular exercise," she says.

It's not a "foolproof" strategy, Viswanathan says: Many otherwise healthy individuals still develop long Covid.

"But I will say their numbers are far fewer," she adds.

Update: This story has been updated to reflect that according to studies, long Covid symptoms can last for at least a year in some patients.

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