Tens of millions of people around the world are believed to have developed long-lasting symptoms and conditions in the wake of a SARS-CoV-2 infection. But this sometimes debilitating phenomenon, often referred to as long COVID, remains a mystery to researchers. What causes it? Who gets it? And perhaps the most maddening: what is it?
Long-term COVID patients have reported a broad spectrum of over 200 symptoms. Some are common, such as loss of smell, while others are rarer, such as tremors. Some patients have familiar constellations of symptoms, others seem to have peculiar assortments.
Researchers hypothesize that long COVID may simply be an umbrella term for a collection of variable — and possibly overlapping — post-COVID conditions that can have different causes. Those causes may include autoimmunity, immune system dysregulation, organ damage, viral persistence, and imbalances in the gut microbiome (dysbiosis).
Unfortunately, while millions continue to grapple with the realities of their conditions, research into long-term COVID is still in its infancy. But a study published Thursday in JAMA offers a hopeful small step toward understanding the condition. Using data from 9,764 participants, researchers narrowed down the more than 200 symptoms of COVID to a weighted list of 12 core symptoms. The list is not a definitive definition of long COVID as it needs to be validated in further studies. But it’s a start. It could help guide further research, identify different subtypes of long COVID and develop diagnostic tools, such as biomarkers.
The study – part of the National Institutes of Health’s Researching COVID to Enhance Recovery (RECOVER) Initiative – examined symptoms and conditions in people with a previous SARS-CoV-2 infection (8,646 people) and those without (1,118). Researchers looked at the frequency of each identified symptom and the symptoms that differentiated the infected from the uninfected.
They arrived at a core list of 12 symptoms and assigned each symptom a score that represented the likelihood it was related to COVID-19. The scores for each of the 12 symptoms ranged from 1 to 8, and the researchers added up the symptom points for each person in the trial. Based on the spectrum of score totals observed in uninfected people, the researchers concluded that a score of 12 was a reasonable cut-off point for determining whether someone had had COVID for a long time. And that boundary was validated when they looked at how it correlated with the participants’ reports of quality of life and health.
Here is the list of 12 symptoms and their scores:
| Symptoms | To score |
| Loss of smell or taste | 8 |
| Post-exertional malaise (feeling tired after light physical or mental activity) | 7 |
| Chronic cough | 4 |
| Brain fog | 3 |
| Thirst | 3 |
| Palpitations | 2 |
| Chestpain | 2 |
| Fatigue | 1 |
| Changes in sexual desire or ability | 1 |
| Dizziness | 1 |
| Gastrointestinal symptoms | 1 |
| Abnormal movements | 1 |
| Hair loss | 1 |
