Three years later the pandemic frenzy has settled into a rumbling buzz. We’re sweating it out in nightclubs again, blowing out birthday candles and holding steady hands. Covid-19, while still very much alive, has become an everyday threat for most people thanks to vaccines and treatments.
The same cannot be said for Long Covid, the mysterious life-limiting disease that persists after an initial Covid infection. For the millions she besieges, her situation has remained much the same. “We still don’t have established tools to treat patients,” says Linda Geng, co-director of the Post-Acute Covid-19 Syndrome Clinic at Stanford University. Estimates of how long people have had Covid vary, but it’s estimated at around 65 million – about the size of the population of France.
It is only now, more than three years after the pandemic began, that a consensus on how long Covid lasts is beginning to solidify. And what it is, turns out, is a whole bunch of things. Rather than a single disorder, it’s more of a hodgepodge of diseases falling under one big umbrella. That means there probably won’t be any one-size-fits-all treatment either.
What long triggers Covid for you may not be what triggers it for another. Perhaps your long covid is caused by your immune system attacking you and attacking your body – a phenomenon called autoimmunity. That’s one theory. Or maybe fragments of the virus hang around in your body long after the initial infection, keeping your immune system’s engine revved to the point of exhaustion. Another theory is that SARS-CoV-2 causes long-term damage to specific organs or tissues. Perhaps a Covid infection awakens latent viruses that your body has encountered before, like the Epstein-Barr virus that causes mononucleosis.
All of these theories have some evidence to support them, and they may not be mutually exclusive; For some people, these things could happen simultaneously. The idea that long Covid has different causes could explain the sheer variety of up to 200 symptoms.
Based on that, the researchers are trying to kill two birds with one stone: they’re testing treatments that could alleviate long-standing Covid, while also lending weight to certain hypotheses — and beginning to unravel the puzzling condition. “The fact is that the urgency is so great that we have to do these things in parallel,” says Geng. “It builds the ship while we sail it – but we have to sail it because people need help.”
But the jumble of symptoms makes designing clinical trials much more difficult. Not everyone has every symptom, and these can vary in severity and duration. Also, there is no consensus on how to define long Covid, says Steven Deeks, a physician and infectious disease specialist at the University of California, San Francisco. “There is no magic biomarker, there is no x-ray, there is no test.” For this reason, it is difficult to know who to include in a clinical trial. For now, long Covid diagnoses work by exclusion: finding that symptoms cannot be explained away by another cause. Regardless, the researchers are plowing ahead.