Long Covid: 200 symptoms, 145 million affected, no known cause – and no shortage of theories about what triggers the virus hangover
- As many as one in five people who get Covid-19 suffer fatigue, breathlessness and brain fog months after their initial infection. Doctors don’t yet know why
- Immune system disruption, blood clotting and the continued presence of coronavirus spike protein are possible causes, according to researchers’ theories
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Millions of people around the world are believed to suffer from long Covid. Although little is known about the condition, recent research has proposed several theories for its cause.
The US-based Institute for Health Metrics and Evaluation (IHME) estimates that nearly 145 million people worldwide had at least one of those symptoms in 2020 and 2021.
In Europe alone, 17 million people had a long Covid symptom at least three months after infection during that time, according to IHME modelling for the World Health Organization (WHO) recently published.
These millions “cannot continue to suffer in silence”, WHO Europe director Hans Kluge said, calling for the world to act quickly to learn more about the condition.
Researchers have been racing to catch up but the vast array – and inconsistency – of symptoms has complicated matters.
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More than 200 different symptoms have been ascribed to long Covid so far, according to a University College London study.
“There are no symptoms that are truly specific to long Covid but it does have certain characteristics that fluctuate,” said Olivier Robineau, the long Covid coordinator at France’s Emerging Infectious Diseases research agency.
“Fatigue remains in the background,” he said, while the symptoms “seem to be exacerbated after intellectual or physical effort – and they become less frequent over time”.
One thing we do know is that people who had more severe initial cases, including needing to go to hospital, are more likely to get long Covid, according to the IHME.
Researchers have been pursuing several leads into exactly what could be behind the condition.
A study published in the journal Clinical Infectious Diseases in September found that Covid’s infamous spike protein – the key that lets the virus into the body’s cells – was still present in patients a full year after infection.
We are not going to find a single cause to explain long Covid. The causes may not be exclusive
If they are right, a test could be developed to identify the spike, potentially leading to one of the great and elusive goals of long Covid research – a clear way to diagnose the condition.
However, their findings have not been confirmed by other research, and several other causes have been proposed.
However “for each of these hypotheses, the data is not very solid yet”, Robineau said. It is most likely that “we are not going to find a single cause to explain long Covid. The causes may not be exclusive. They could be linked or even succeed each other in the same individual, or be different in different individuals.”
Treatment also remains elusive. For the past year, the Hotel-Dieu hospital in Paris has been offering long Covid patients a half-day treatment course.
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“They meet an infectious disease specialist, a psychiatrist, then a doctor specialising in sports rehabilitation,” said Brigitte Ranque, who runs the protocol dubbed Casper.
“The patients are brought back in three months later. The majority of them are better. More than half say they are cured,” she said. “But about 15 per cent did not improve at all.”
