Today, James is feeling about a two out of five. The young lawyer is reasonably articulate on the phone. He might be able to read a single news article today, maybe even go for a short walk. On a “five out of five” day, he can do four hours of lighter duties – analysing legislation, some emails – but nothing like the intense legal work he was doing full-time eight months ago.

When he’s at zero, he’s immobilised on the sofa, unable to compose a two-sentence text message or string together enough words to speak to his partner, Matilda. Getting up to go to the bathroom is a marathon. The sound of a plastic bag crinkling is like someone screaming in his face.

James, whose name has been changed, spends half the day battling to stay awake. At night, he can’t sleep for more than four or five hours. His heart is constantly racing and he is plagued by intense headaches. If he has two good days in a row and makes the most of that, the price is being back at zero for the following three or four days: “Basically a living, breathing shell,” he says.

This is long Covid. James’s symptoms are severe, but an estimated 400,000 Australians are in a similar boat. With Omicron surging again, that number is going to increase. Estimates of the rate of long Covid in people who have been infected with SARS-CoV-2 range from 5 per cent all the way to 50 per cent, depending on the definition, the population studied, and the time frame used.

“I think we land in the area of, crudely, let’s say 10 per cent of people who’ve been infected having long Covid at the three-month point, which is the critical point where it’s really ‘long Covid’,” says health economist Professor Martin Hensher, the Henry Baldwin professorial research fellow in health system sustainability at the University of Tasmania.

More than eight million cases of Covid-19 have been diagnosed in Australia since the start of the pandemic and, says Hensher, “the fundamental problem is 10 per cent of a big number is a big number”.

Hensher and colleagues did some modelling in the second half of 2021 – before Omicron appeared – looking at the overall burden of Covid-19 in Australia in terms of disability-adjusted life years, or DALYs, where one DALY represents the loss of one year of good health. Their modelling included DALYs lost because of death, severe illness, mild illness and ongoing illness.

They found that persistent illness, in the form of long Covid as well as conditions precipitated by Covid-19 infection, including diabetes and heart disease, was likely to account for about half of the total health burden of Covid-19. Long Covid alone represented about 10 per cent of Covid-19’s health impact. That was before Omicron.

Now, Hensher thinks, long Covid will make up an even greater proportion of the health burden of Covid-19, because deaths are going down but infection numbers are going up.

He and his colleagues are gearing up to rerun their model with more recent data, but a key challenge is defining long Covid. He says “the critical missing piece in all the current discussion” is clarity around how many people are really disabled by it versus those people for whom it is “thoroughly unpleasant and highly inconvenient”.

In December 2021, the World Health Organization put out its first clinical definition of long Covid, or what it calls “post COVID-19 condition”. Key features are probable or confirmed SARS-CoV-2 infection, and symptoms that have lasted for at least two months and aren’t explained by any other diagnosis. Those symptoms might have persisted after the first, acute phase of infection, or started just after recovering from the initial infection.

At Anthony Byrne’s long Covid clinic at St Vincent’s Hospital in Sydney, they treat patients who have had persistent symptoms for at least 12 weeks, “but the key thing for that is that they’re symptoms that weren’t there before, and they’re there now, and they’re not explained by something else”, says Byrne, a chest physician and associate professor at UNSW Sydney.

Byrne has treated patients from age 18 to 80, men and women, in all states of health or illness before Covid-19 hit them. “There is a broad spectrum of what a long Covid patient looks like,” he says. “It can look like anyone.”

What they do have in common are symptoms of crushing fatigue and lethargy, breathlessness and “brain fog”. Some also have chronic pain, headaches or insomnia. These symptoms have to be pretty severe: James qualified as a patient, but his partner, Matilda, did not, despite months of being unable to work more than a few hours a day, drive for more than 20 minutes without pulling over to rest, or walk and text without needing to sit down. Both Matilda and James caught Covid-19 in early December 2021, so they’re now past the seven-month mark of persistent, debilitating symptoms.

The symptoms of long Covid will be unpleasantly familiar to anyone who has experienced post-viral fatigue or chronic fatigue syndrome/myalgic encephalomyelitis. There’s a number of important similarities between all these conditions, says Dr Natalie Eaton-Fitch, a research fellow with the National Centre for Neuroimmunology and Emerging Diseases at Griffith University. “Both ME/CFS patients and long Covid patients present with brain fog or the cognitive difficulties,” she says. “There’s the post-exertional fatigue, the respiratory symptoms – they’re also present in ME/CFS, as well as long Covid.” 

ME/CFS has been around a lot longer than long Covid but researchers are still largely at the hypothesis-generating stage of explaining its underlying causes. However, given the massive impact and cost of long Covid, and the substantial global research effort to understand and treat it, the hope is that scientific explanations will be found much more quickly.

There are some leading scientific hypotheses about the underlying causes of long Covid that fit broadly into the categories of immunological or neurological explanations.

The first thing to note about long Covid – as well as post-viral fatigue – is that despite the crippling symptoms, people with the condition have relatively normal function in all the organs that seem to be affected. It’s a paradox that has puzzled infectious diseases physician Professor Andrew Lloyd for 30 years of researching and treating post-viral fatigue.

“People report a lot of difficulty, but if you try and measure it – this is true in post-viral fatigue as well – you can show a little bit, like milliseconds, of delayed reaction time or slightly reduced performance in … what we’d call executive tasks, but they’re pretty subtle,” says Lloyd, head of the viral immunology systems program at the Kirby Institute, and director of the UNSW Sydney Fatigue Clinic and research program.

Similarly with breathlessness: a person with breathlessness related to asthma or lung disease will be puffing hard after going up a flight of stairs. But a person with long Covid can walk up that same flight of stairs and,  although they feel subjectively breathless at the top, they can still have a conversation.

“If you do brain scans, and structural scans like MRI, there’s a brain there and it looks for all intents and purposes normal in size and shape,” Lloyd says. “There’s not much to find structurally, which leads us to suspect that it’s a functional disturbance.”

Lloyd points to post-viral fatigue research using functional magnetic resonance imaging, which gives an indication of levels of activation in different parts of the brain in real time while someone performs certain tasks. This suggests that people with post-viral fatigue have a greater degree of activation during tasks, such as tapping their finger or thinking about something specific, compared with people without post-viral fatigue. “It’s like the system’s not operating as efficiently as you’d like to get the output,” he says, “and so you’ve got to work harder.”

So what’s causing this apparent inefficiency? One theory is that inflammation in the brain is the culprit. Neuroscientist Dr Leah Beauchamp, from the Florey Institute of Neuroscience and Mental Health in Melbourne, first became interested in the neurological effects of Covid-19 when she started hearing reports of people losing their sense of taste and smell. As a researcher in Parkinson’s disease, she knew those losses were also a possible harbinger of neurodegenerative disease, and that worried her.

The initial loss of taste and smell that characterised acute SARS-CoV-2 infection in the pre-Omicron era was considered par for the course of an infection that got into the cells lining the nasal passages. “During other viruses, you do lose your sense of smell but again, it’s acutely: it’s for a couple of weeks or a month, because you’re really inflamed and congested,” Beauchamp says. The persistent loss in long Covid isn’t normal, and suggests that inflammation has actually penetrated into key regions of the brain associated with olfaction. “These factors that are inflammatory from your system can get into your brain and it triggers a cascade,” she says, “and once you’ve triggered neuroinflammation, it’s very hard to rein that back in.”

The other support for a critical role of inflammation comes from immunology. At the Kirby Institute, Dr Chansavath Phetsouphanh and colleagues were comparing immunological markers in people with long Covid against those of people who had experienced Covid-19 infection but had recovered without persistent symptoms. This showed elevated levels of certain proteins involved in the immune response to viral infections, called interferons, even at eight months after their initial infection, which suggests ongoing inflammation.

Patients with long Covid were also missing a type of immune cell called a true naive T cell, and the researchers suspected these were being constantly switched over into an activated T cell. “They’re not meant to be activated,” Phetsouphanh says. “It just goes into what we observed with interferon, so it seems like there’s ongoing inflammation in long Covid patients, and it’s activating the immune system.”

Inflammation is a modern bugbear, seemingly behind a host of chronic conditions including diabetes and heart disease. While drugs known as anti-inflammatories exist, they are hopelessly outgunned by system-wide, entrenched inflammation. This makes treating and managing long Covid difficult but not impossible.

“We know that over the last two-and-a-half years, people get better. They do get better. But it’s everything in super-slow motion,” Byrne says. “So what we’re looking to do is reassure, diagnose and assist with getting people back.”

For James, that assistance has taken the form of breathing exercises, tai chi, cold therapy such as ice baths, stretches, and being very, very careful with how much he tries to do in a day. “A lot of it is finding the right balance and giving me a framework to figure out – if I’m trying to return to work, which I am, do I try to do this much exercise and this many hours, or fewer hours and more exercise, or what kind of exercise?” he says.

Despite countless blood tests, scans, and visits to neurologists, cardiologists, physiotherapists, psychologists and sleep physicians, no obvious treatment targets have yet presented themselves. The most emphatic point made by many experts is that the best treatment for long Covid is prevention – not getting Covid-19 in the first place. Byrne has observed that the more acute Covid-19 symptoms someone gets, the more likely they are to go on to long Covid, which makes a strong case for avoiding infection or getting vaccinated to reduce the risk of severe infection.

Another clarion call from the medical and scientific community is for us to not repeat the mistakes of the past when it comes to recognising and managing long Covid. “We have some terrible examples from the way that we’ve responded to prior issues like chronic fatigue syndrome, where people have not acknowledged the physical and the psychological impacts of that,” says Professor Maree Teesson, director of the Matilda Centre at the University of Sydney.

Given the massive impact long Covid has on mental health, such as brain fog, anxiety, depression and insomnia, Teesson hopes that patients with the condition won’t be subjected to the same stigma that has met patients with ME/CFS, and that they will be given all the best, evidence-based treatments available. “I’m really hopeful that we’ve got a government and we’ve got a Health minister who is already discussing long Covid and is hopefully prepared to respond.”

She also notes that Australia’s already strained health system, especially mental-health services, will not cope with a huge influx of chronic disease. “Quite frankly, our mental-health system is not coping at the moment, let alone coping with another 400,000 people with additional mental-health symptoms associated with long Covid.”

Professor Andrew Baillie, convenor of the Long-COVID Australia Collaboration, makes a similar point. “The NDIS isn’t really, I don’t think, ready for this.”

Baillie, who is also a clinical psychologist at the University of Sydney, would like to see income support provided for people with long Covid who have used up their sick leave but are still unable to work.

He also says Australia needs to know exactly what it’s dealing with. “I think at the moment somehow we’ve got our head in the sand; we’re not even looking, so we don’t know how big a problem it is.”

There are currently no registers tracking long Covid cases, or any centralised data collection at the state or federal level. In contrast, Britain has implemented large-scale household surveys that are giving some sense of how widespread the condition is.

Most importantly, however, Australia needs a plan for long Covid that is as agile and responsive. “Covid is not going anywhere,” Baillie says, “and the more Covid cases we have, the more long Covid we’re going to have.”

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