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Karren Hill was among the first Australians to catch COVID-19 when she fell sick in April 2020. And she was one of the first to discover they weren’t getting better.
She struggled to breathe, was exhausted, had a brain full of cotton wool and a headache that wouldn’t ease. All symptoms of long COVID – a term that hadn’t yet been coined.
Karren Hill, who has long COVID.
“When I was having the breathing problems, I came straight to the hospital – and they didn’t want to see me,” said Hill. She eventually went to see a cardiologist. “He didn’t really believe in long COVID, and he hadn’t really heard much about it.”
As the federal government announced $50 million for research into long COVID this week, Hill’s story is common in depictions of the illness: a mysterious illness, a battle for diagnosis, no treatment.
But interviews with some of Australia’s leading long COVID researchers suggest they don’t see it that way. Indeed, that narrative frustrates many.
“We have arbitrarily called this long COVID. There’s no science to it,” said Professor Craig Anderson, director of brain health at the George Institute and lead investigator of a long COVID clinical trial.
Rather than a single illness, some now believe what we call long COVID is actually several distinct disease processes.
“There is a misperception that there is a single long COVID – and I just think that is so wrong,” said Professor Tom Marwick, who is leading a study of long COVID at the Baker Institute. “When we clump stuff together, that is really the enemy of understanding mechanism and therefore targeting the cause of the problem.”
But advocates and other researchers push back against this view, which they see as not taking into account the complexity of long COVID.
“This view comes from those who don’t understand post-viral conditions,” said Marie-Claire Seeley, chief executive officer of the Australian POTS Foundation. “They like to separate everything down to singular organisms but this can’t be done here.
“Post-viral syndromes are an extraordinarily complicated interplay of immune and nervous system responses. They are complex and can’t be neatly siloed into discrete categories.”
And long COVID patients, who have already had to fight so hard for a diagnosis, worry this will just make things worse.
“Getting too specific about mechanisms too early could have a negative effect of even less patients getting a diagnosis, when it is already hard to get the support and treatment we need,” said Ruth Newport, an administrator of the Australia Long Covid Community Facebook group.
The definition problem
Long COVID is the first illness to be defined by patients who came together on social media. Getting recognition required enormous advocacy; it took until late 2021 for the World Health Organisation to formally recognise and define the disease.
But this long-fought-for definition – which includes a large number of symptoms ranging from altered smell to chest pain to pins and needles to brain fog – is simply too broad, several researchers said.
“It’s a complete dog’s breakfast,” said Professor Andrew Lloyd, director of the University of NSW fatigue clinic.
University of Newcastle Professor Peter Wark, a respiratory physician focused on long COVID, says we need to be “not so obsessed with the label”. “Almost any problem you have after COVID could suit that definition – you just have to wait three months.”
Rather than a single disease, it is likely long COVID is instead several distinct disease processes, the researchers said.
Consider a key risk factor for long COVID: getting so sick with COVID you end up in hospital.
Could this group simply be seeing the after-affects of a violent illness? About 25 per cent of people who survive an ICU visit are left with cognitive and physical damage – a condition known as post-intensive care syndrome.
“When you’re in intensive care, it’s a very harrowing experience,” said Lloyd. “And to get there, you have to be in a life-threatening situation. And so there’s lots of organ injury.”
Another subgroup’s illness may be driven by chronic inflammation, a leftover from their battle with the virus. Other groups may have symptoms driven by viral reactivation or persistent infection. Still others might have a post-viral illness similar to glandular fever – an illness caused by Epstein-Barr infection that can cause months of fatigue.
“[Long COVID] is a real condition – but we see it in people who have had other types of severe infections,” said Anderson.
Other researchers say this view misses the complexity of the disease.
Hannah Davis co-leads the Patient-Led Research Collaborative; she headed a major review of long COVID published in Nature Reviews Microbiology earlier this year.
There are likely multiple causes of long COVID – but these causes overlap, her review found.
“Inflammation from COVID likely causes viral reactivation of latent viruses, which can cause downstream impacts including nerve injury and microclots,” she said.
“The best researchers generally understand that it’s going to be an ‘and’ scenario.”
Trials and treatments
The problem with definitions turns from theoretical to practical when scientists recruit long COVID patients to clinical trials.
If the definition of long COVID captures multiple different disease processes, the data gathered at the end of the trial will make little sense – making the disease seem mysterious. Said Lloyd, again, “it’s a complete dog’s breakfast”.
In 2021, Marwick launched a study looking at the hearts of patients with long COVID – guessing fatigue and breathlessness might be warnings of cardiac problems.
They did find heart changes – but only in about 15 per cent of the patients they studied (the study has not yet been published).
His group also looked for signs of postural orthostatic tachycardia syndrome, which impairs blood flow to the brain and can cause brain-fog and fatigue. Again, some patients had it – but not all.
“It’s not at all what we were expecting,” he said. “There is a misperception that there is a single long COVID – and I just think that is so wrong.”
He argues the same issue limits the ability to develop good treatments for long COVID.
In the US, long COVID patients and advocates have been protesting against plans for a government-funded trial of exercise therapy – arguing the treatment is harmful.
Some long COVID patients have post-exertional malaise, meaning exercise therapy can leave them bedridden for days. And the evidence for exercise therapy for chronic fatigue syndrome is deeply controversial.
As part of his trial, Marwick treated the patients with heart issues with a standard program of graded exercise therapy. Every one of them got better.
“I’ve had the pushback against the advocates,” he said. “Because I can take them to a dozen people we’ve exercised who say ‘I feel better, and I can do things I haven’t done before.’ ”
It is plausible different subgroups of long COVID will need different treatments, Marwick said. But we can’t prove that until we start breaking down the definition.
“We have a group of people who could respond to the treatment, but they are absolutely drowned by the people who won’t.”
Hannah Davis is sceptical. Knowing the exact mechanism of an illness is not a requirement for testing treatments, she argues. “That’s happened in many diseases, all of the time.”
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