Erin Sharoni is a biology master’s student at Harvard who studies longevity. At 39, it’s not just an academic interest. She’s fashioned her life around ensuring she’s healthy: exercising daily, meditating regularly, eating only vegan foods and tracking her biomarkers.

Sharoni took the coronavirus seriously, but she admits she often thought to herself, “I really don't want to get it, but if I do get it, then I'll probably be OK.”

In November, she tested positive for the virus. She still has no idea exactly how she contracted it. Now, several months later, she said that she’s definitely not OK.

“I never would have thought that this would have happened. No way," Sharoni said in a phone interview from Florida, where she is now living. "

Sharoni is among the tens of thousands of people in the U.S. with what's being called "long COVID." She and her fellow "long-haulers," as they're known, suffer from debilitating symptoms many months after getting sick. Medical professionals are still trying to understand the biology and treatment options for COVID-19 long-haulers, along with exactly how many people fall into this category.

Researchers estimate that somewhere between 30% and 50% of people who contract COVID-19 will have symptoms that linger three months after getting sick, but a smaller number — likely between 3% and 10% — have debilitating symptoms for far longer.

Studies suggest that those long-term symptoms don't necessarily come on as a result of a more severe initial infection.

“People who have had, quote-unquote, mild or moderate disease — who have not required hospitalization — can still have complications either of specific organ groups, such as respiratory or cardiovascular or neurologic, but they can also have more global symptoms,” said Stephen Martin, physician and professor of family medicine and community health at UMass Medical School.

One recent study found that more than 30% of long-haulers initially had an asymptomatic infection.

Sharoni was not one of them. She first knew something was wrong when she was in the bathroom washing her face.

“I looked up at the mirror and my whole body felt like a noodle,” she said. “I felt like a piece of spaghetti and my bones were just going to collapse.”

Next, she noticed neurological changes.

“I began to have these lapses in memory where it was almost like blacking out,” Sharoni said.

It took about two weeks before her body fought off the virus. But, even with her COVID-19 tests coming back negative, Sharoni was not back to normal — not even close.

The mental fog and fatigue that started during the acute phase of her infection have not yet fully resolved. And, she said, other symptoms emerged, too.

She remembers sitting at her desk writing emails when, out of nowhere, she began to feel ill.

“My heart rate just completely shot through the roof," she said. "And with that I had cold sweats, this weird tightness in my chest, neck and back pain, a little bit of feeling of nausea and blurred vision.”

These episodes continued. She ended up seeing lots of doctors. Among other things, they noticed inflammation in her heart. Her cardiologist told her that he’s seeing a baffling number of patients — two or three people a day — who are like Sharoni: young, healthy and with severe post-coronavirus complications.

One recent study found that the virus that causes COVID-19 seems to be able to directly infect heart muscle cells — and kill them. But still, Sharoni said, a lot is unknown.

"They don't know how to control it or what to do with it or why it's happening or how long it's going to happen for,” she said. “So, to me, there's this great sense of extraordinary frustration, frustration of like, why me?”

Sharoni has coped by reading the latest research on COVID-19 long-haulers. And she stays as busy as possible, pouring herself into her master’s thesis, working on a tech start-up that incentivizes people to buy more plant-based food and writing a vegan cookbook. She’s also been forced to spend many hours on the phone navigating the world of exorbitant medical bills. While Sharoni is impressively productive, it’s no easy feat given that — as she said — her brain’s synapses aren’t back to normal yet.

She’s willed herself into keeping an upbeat, optimistic attitude, reminding herself that other people have it worse. But, she acknowledged, she’s afraid about what would happen if she pauses to think about all the stress and fear in her own life.

"There have been moments where, you know, you're by yourself in your apartment at night," she said. "And you just cry, because it's really scary and frustrating and disappointing and unfair."