It’s been about 10 months since Kary Martin caught COVID-19 from a patient who had a false negative. And since then, she hasn’t worked.

Prior to the COVID-19 pandemic, Martin served primarily as a respiratory therapist in a newborn intensive care unit. But with her skills in high demand as more and more COVID patients flooded the Sacramento-based hospital where she worked, Martin served in intensive care and step-down COVID units, putting her on the front lines of the pandemic.

Last November, she spent a couple of nights working with a patient who initially tested negative for COVID, but eventually tested positive. “I ended up going home sick one night because I just was not feeling good—I had this massive headache. The next morning I woke up, and I couldn’t smell anything or taste anything, and I’m like, ‘Shit, I’ve got COVID,’” Martin told Fortune.

Even once the worst of her initial COVID symptoms had passed while she convalesced at home, Martin said she still didn’t feel right. In fact, she went to the hospital in December worried she had a pulmonary embolism. While they didn’t find an embolism, scans showed heart inflammation.

Since then, Martin has been dealing with the effects of long COVID, also known as post-acute COVID-19 syndrome. That means Martin has been doing everything from seeing specialists to attending pulmonary rehab and a neuro clinic, which focus on physical therapy, occupational therapy, and speech therapy to help relieve some of the brain fog and memory issues. “I have a great team that’s helping me, but they’re all learning,” Martin said.

She’s hopeful that she’ll be back to work by the end of this year, but right now, she doesn’t feel she can do her job. “Right now I’m not safe with patients,” Martin said. Instead, she’s on workers’ compensation, which pays about 60% of her salary and takes care of the medical expenses.

“It is a financial burden,” Martin said, but added that she’s lucky—she didn’t have to fight with her employer to provide workers’ comp, and it has approved every treatment without pushback.

It’s recently become easier for workers like Martin to file for workers’ comp, but not everyone is so fortunate. Whether you can get workers’ comp for long COVID varies widely, depending on your job and where you live.

Different states, different rules

Martin works in California, which passed laws in September 2020 that require most employers to presume an in-person worker who contracts COVID-19—including first responders, farmworkers, grocery store employees, and warehouse workers—did so in the workplace and is therefore covered by workers’ comp.

Workers’ comp rules vary dramatically state by state. About 16 states have introduced or passed legislation that would allow employees who suffer from a communicable disease like COVID-19 to file workers’ compensation claims presuming they contracted their illness at work, according to the National Council on Compensation Insurance.

Many of these laws have made it easier for essential workers—nurses, doctors, first responders, and restaurant and retail employees—to receive workers’ comp after falling ill with COVID-19. But not everyone is covered.

“State laws do differ, but if an employee can show that they contracted COVID In the course of their employment, then their claim will be paid,” Jeff Eddinger, NCCI’s senior division executive, told Fortune.

COVID claims can present unique challenges

Tying a case of COVID-19 directly to work can be challenging. Because this virus is contracted so easily, especially the new Delta variant, proving beyond a shadow of a doubt that an employee caught it at work can often be tricky. As Eddinger noted, workers can potentially catch it anywhere—at a party, a sporting event, or a concert—so how do they prove to their employer that they caught it on the job?

Additionally, some employees may not have filed an initial claim form because they didn’t get a severe case when they contracted COVID. Instead, they file a claim months later because of ongoing symptoms of long COVID. Liberty Mutual notes that deciding whether or not to accept these types of claims may involve extended investigation.

But COVID cases are also a different breed when it comes to navigating the workers’ comp system. “The vast majority of [workers’ comp] claims are really muscular type injuries,” said Max Koonce, chief claims officer with Sedgwick Claims Management Services. “When you look at those injuries, they have a very established protocol as to how they’re treated; they have evidence-based medicine guidelines that they use, so you have a pretty good idea of the way the claim is going to go as far as with medical treatment,” Koonce noted.

With COVID, however, it’s a brand-new virus with multiple symptoms, varying lengths, and a whole host of potential treatment options. “Your typical workers’ compensation injuries don’t have these long-term symptoms or conditions that you’re seeing creep up within the COVID environment,” added Koonce.

The Wall Street Journal found in February that a significant number of workers’ comp claims related to COVID-19 have been denied—up to 56% in some instances. A report from Willis Towers Watson found that the denial rate at one major claims adjuster was much lower: 37% COVID-only claims were denied nationwide, compared with denial rates of 11% prior to the pandemic.

Overall, workers filed more than 45,000 COVID-related claims in 2020, according to NCCI’s State of the Line report.

Yet the vast majority of those COVID-19 claims are very small, Eddinger said, noting that those cases are ones that don’t require hospitalization in which workers are only out of work for a few days or a week.

In fact, only about 1% of claims turned into expensive claims totaling over $100,000 where a worker was sick with COVID-19 for a very long time, he added. But those 1% of claims accounted for 60% of the total payouts.

“Even though there are some claims that ended up being very expensive, because there’s so few of them, I wouldn’t expect there to be a measurable impact on the total workers’ comp system costs,” Eddinger said.

Not everyone files for workers’ comp

Part of the reason that these COVID claims aren’t overwhelming the system could be that some workers aren’t even bothering to attempt to file. Fran Highhouse works as a caregiver at a Pennsylvania-based facility for those with disabilities. In November, a few workers came down with COVID-19, including Highhouse.

Her initial infection was so bad that she was hospitalized and ended up out of work for about four months. But her employer refused to admit she contracted COVID at work and even fought her unemployment claim. “They were demanding documentation while I was still in the hospital, and the only thing on me was a cell phone. I wasn’t capable of doing anything while I was in there,” Highhouse recalled.

Once she had used up her unpaid time off through the Family and Medical Leave Act, Highhouse said she had to return to work. “They said, ‘Your FMLA is up, you come back to work or you’re terminated, but you’re more than welcome to apply again,’” Highhouse said. Worried she wouldn’t get unemployment or disability, Highhouse said financially, she had no option but to go back, despite lingering brain fog and fatigue.

Still in uncharted territory

While most of the COVID claims have been relatively small so far, there’s a chance that could change as long COVID cases develop. Estimates of the number of patients who suffer from long COVID range from 2.3% to 37% of those who test positive, according to a report published in the U.K.

If the percentage of patients who suffer from long COVID ends up on the higher side, it could have widespread consequences. The Workers’ Compensation Insurance Rating Bureau of California examined the potential cost impact and estimated that presuming employees contracted COVID at work could cost the industry $1.2 billion in workers’ comp claims. Meanwhile, NCCI found that last year, carriers reported $260 million in total COVID-19 incurred losses.

But so far, Koonce says that the data doesn’t show an overwhelming number of long COVID cases in the workers’ comp system. “I think inevitably there will be some type of uptick," he said, "and how big it is, I don’t know.”

Yet the uncertainty of COVID means there are many workers out there who are struggling to get the help and support they need. A member of the Long COVID Alliance, a support group for those navigating the effects of long COVID, Martin says she’s seen heartbreaking stories.

“There are so many people that are just desperate for medical help, and they don’t have insurance or their job does not acknowledge their exposure for work. There are horror stories. I’m really blessed,” Martin said.

She hopes to be back to work in a few months, but she’s still unsure of that timeline. “I’m trying to be really positive because this has been such a negative experience,” Martin said, adding she needs to believe there’s a light at the end of the tunnel.