MICHEL MARTIN, HOST:
Why is long COVID so perplexing? Scientists met this week to address the persistent symptoms that some people develop in hopes of figuring out the cause or causes and how to treat them. NPR's Will Stone has this report.
WILL STONE, BYLINE: Dr. Rasika Karnik first started seeing long Covid patients in her clinic at the University of Chicago all the way back in the fall of 2020. She says at least now, there are a lot more studies and doctors who know about it.
RASIKA KARNIK: So I feel a little less out in the wilderness. But it's still there. There's not the same rigorous evidence for treatment. And there's no diagnostic yet.
STONE: Her approach is basically to rule out other illnesses, treat her patients for whatever symptoms they do have, sometimes use medications off label. And she tries to be honest that scientists still don't know what's driving the illness.
KARNIK: Do I wish things were faster? Of course I would. It's hard to look a patient in the eye and say, we're not quite sure yet.
STONE: Karnik was at the long COVID conference in Santa Fe held by the nonprofit Keystone Symposia. Dr. Steven Deeks at the University of California, San Francisco was one of the organizers. He says the reality is decoding a complex, hard to define illness like long Covid takes time.
STEVEN DEEKS: You need to describe it. That's kind of happening. Then you need to figure out the epidemiology. How common is it? Who's at risk? How long does it last? We're sort of there. Then you got to figure out the mechanism, right? And that's basically the focus now.
STONE: What makes this so challenging is that long COVID doesn't present in just one way. There tend to be different clusters of symptoms, which suggests there may be numerous underlying causes. Dr. Catherine Blish at Stanford University says this matters when you start to set up trials to test treatments.
CATHERINE BLISH: We need to understand in detail who's most likely to benefit from those because if we just take everyone, that trial will fail.
STONE: Scientists have now largely coalesced around a handful of explanations for what could be driving long COVID. There's clear evidence of dysfunction within the immune system, of viral reservoirs - meaning parts of the virus linger in the body - of widespread inflammation in the blood vessels and harmful clotting and of other viruses, specifically the Epstein-Barr virus, being reactivated. Some of these could be interrelated. They could be happening in certain patients but not others.
BLISH: We have at this point hints and correlative data. Like, we can say we see this in this subset of people. But just because we see a finding in a subset of people doesn't mean it's the cause.
STONE: Take, for example, this theory that viral persistence is causing long COVID. Dr. Michael Peluso at the University of California, San Francisco says they're now confident these pieces of viral proteins are in the blood of long COVID patients. But that's not the end of the story.
MICHAEL PELUSO: We're more likely to find this in people who are sort of the most symptomatic. But not everybody with long COVID has this. And then really importantly, we're also seeing this in some people who feel totally fine, and we don't know what that means.
STONE: These are the types of thorny questions that are still hanging over long COVID researchers. Peluso has just launched a trial to see if an anti-COVID monoclonal antibody can help patients. Lisa McCorkell is with the advocacy group Patient-Led Research Collaborative. She's energized by the progress scientists are making, but she worries they don't have enough support.
LISA MCCORKELL: What we really need here is pharma engagement. We need industry engagement. We need funding for clinical trials.
STONE: Because that's how all of this research will turn into actual treatments. Will Stone, NPR News. Transcript provided by NPR, Copyright NPR.
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