Understanding Long Covid: Challenges and Definitions
By 2025, a consensus was forming among experts. “I think it’s pretty much accepted now that long Covid is a biological disease,” remarked Igho Ofotokun from Emory University School of Medicine during the Long Covid International Conference. “It’s not just in your head. It’s a real issue.” He also highlighted a significant hurdle in scientific research: “The big elephant in the room is that we lack a gold-standard definition for long Covid. This complicates everything, from creating clinical trials to tracking outcomes.”
One major challenge in defining long Covid is the absence of clear biomarkers—things like genes, antibodies, or any unique physiological indicators specific to the condition. To find these biomarkers, researchers need to first identify patients suspected of having long Covid and look for commonalities beyond their symptoms. Discovering these identifiers is crucial for creating targeted treatments—whether through gene therapy or antivirals—and for distinguishing between those who genuinely have the condition and those whose symptoms might be caused by something else.
The search for long Covid biomarkers is led by scientific experts. However, this quest hinges on how to classify someone as having long Covid in the first place, a process that has been significantly shaped by patient advocates. Deciding who qualifies for a long Covid study means establishing a set of criteria that can be tricky. If these criteria are too restrictive, they might exclude genuine patients; if they’re too lenient, those without the condition could be included, which poses risks for the integrity of the research.
For patient advocates, strict criteria present another concern: those who feel they have long Covid might not be recognized as such. This issue came to the forefront soon after the pandemic began when the National Academies of Sciences, Engineering, and Medicine (NASEM) aimed to create a “uniform, core definition” of long Covid. Several basic questions lingered then: Is a positive SARS-CoV-2 test necessary? What symptoms are essential? And how long do they need to last?
By 2024, emphasizing “the patient perspective and interdisciplinary discussion,” the committee put forth an “intentionally inclusive” definition, ensuring that individuals experiencing long Covid would fall under this definition. They concluded that long Covid is “an infection-associated chronic condition that follows SARS-CoV-2 infection and persists for at least three months as a continuous, relapsing and remitting, or progressive disease impacting one or more organ systems.” Symptoms may include shortness of breath, cough, persistent fatigue, post-exertional malaise, difficulties with concentration, memory issues, recurring headaches, lightheadedness, rapid heart rate, sleep disturbances, and gastrointestinal problems.
Per the NASEM definition, experiencing just one symptom from this list qualifies as long Covid, regardless of severity. Interestingly, prior infection “may have been recognized or unrecognized”—which means you don’t need to have had a positive test for Covid. In simpler terms, if you’ve been having sleep problems for three months and suspect it’s linked to an unconfirmed case of SARS-CoV-2, then you fit the criteria for long Covid.
