How many people end up with long Covid after an infection, and is the term itself still useful?

As campaigners marked Long Covid Awareness Day by marching through London to the Houses of Parliament and Downing Street yesterday to protest about the lack of effective treatments available for patients living with the condition or with chronic fatigue syndrome (ME), new research from Australia was stirring up controversy by suggesting that Long Covid is actually "indistinguishable" from other post-viral illnesses.

It was "time to stop using terms like ‘Long Covid’ as they wrongly imply there is something unique and exceptional about longer term symptoms associated with the virus", said the researchers.

Their analysis, comparing longer term outcomes after Covid versus seasonal flu and other respiratory infections, found "no evidence of worse post-viral symptoms or functional impairment a year after infection".

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The findings are due to be presented in full at the end of April when the European Congress of Clinical Microbiology and Infectious Diseases holds its annual conference in Barcelona.

However, according to the abstract - issued late on Thursday UK-time - the study was carried out in Queensland and based on 5,112 adults presenting with respiratory symptoms between May 29 and June 25 2022.

The Herald: Dr John Gerrard, the chief health officer for Queensland, Australia, was among the paper's authorsDr John Gerrard, the chief health officer for Queensland, Australia, was among the paper's authors (Image: Getty)

Its authors include Dr John Gerrard, the chief health officer for Queensland and an infectious diseases doctor who treated the region's first known Covid patient in January 2020 as well as the Hollywood film star Tom Hanks when he first fell ill with Covid while filming on the Gold Coast.

According to the paper, their patient sample was made up of 2,399 adults who tested positive for Covid; 995 who tested positive for influenza; and 1,718 who tested negative for both, but displayed symptoms of respiratory illness.

A year on from their PCR tests, in May and June of 2023, the researchers went back to the same group of patients to find out how they were.

Using a questionnaire sent via text message, participants were asked whether they had any ongoing symptoms or functional impairment that limited day-to-day activities.

Overall, 834 people - 16% of the total cohort - reported some form of ongoing symptoms such as pain, breathlessness and fatigue a year on from their original illness.

A smaller number - 184 (3.6%) - said they were experiencing moderate-to-severe functional impairment.

When the researchers ran the analysis to control for variables such as age, sex, and ethnicity, they found that 3% of those who had tested positive for Covid reported moderate-to-severe functional limitations a year later.

That compared to 4.1% for the other 2,713 patients combined, and 3.4% for those who had specifically tested positive for influenza.

The Herald: By mid-2022, most adults were vaccinated and the Omicron strain was prevalent, creating very different circumstances to the start of the pandemic in 2020By mid-2022, most adults were vaccinated and the Omicron strain was prevalent, creating very different circumstances to the start of the pandemic in 2020 (Image: PA)

The findings have been interpreted as evidence for one long-standing proposition: that the sudden global spread of Covid, a novel pathogen, thrust the problem of post-viral syndromes into the spotlight in a way that had never happened before.

As billions of people were infected over a short space of time by a new virus, the inevitable consequence is that a proportion of them would be left with lasting - but not necessarily unique - effects.

Dr Janet Scott, a clinical lecturer in infectious diseases at Glasgow University - who was not involved in the study - noted that "many infections cause post infection syndromes, and it may be that ‘long Covid’ is indeed not markedly different from other post -respiratory virus syndromes".

"The big difference with Long Covid is the sheer number of people infected with the same virus in a short space of time," she added.

To take the Australian study as an example, even if rates of lasting functional impairment were roughly the same between those with Covid and those with influenza, the actual number of 'long Covid' cases a year on was 72 compared to 34 for "long Flu".

Influenza also tends to occur in a winter wave before largely disappearing, whereas Covid is still continuing to circulate all year round which results in many more infections - and thus cases of long Covid - overall.

The Herald: Flu tends to have one winter peak, whereas Covid is circulating at relatively high levels most of the year (ONS Infection Survey - up to March 2024)Flu tends to have one winter peak, whereas Covid is circulating at relatively high levels most of the year (ONS Infection Survey - up to March 2024) (Image: ONS)

The Herald: Number of economically inactive working adults in UK (aged 16-64), May 1993 to January 2024 (in thousands)Number of economically inactive working adults in UK (aged 16-64), May 1993 to January 2024 (in thousands) (Image: Statista)

The toll of long Covid at a population level is repeatedly cited as one of the factors behind the rising number of working age adults who are economically inactive due to ill health, which has soared from around two million before the pandemic to 2.7 million now.

Deteriorating mental health and record NHS waiting lists have also been blamed, of course. Before Covid, there were just 121 people in Scotland who had been waiting over two years for a planned hospital procedure; today that stands at 7,170.

For Dr Gerrard, the findings suggest it is "time to stop using terms like ‘long Covid’" because such terminology "can cause unnecessary fear" and "wrongly imply there is something unique and exceptional about longer term symptoms associated with this virus", particularly in a highly vaccinated population.

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His message, essentially, is that anyone suffering from a post-viral syndrome - be it long Covid, ME, Lyme disease - has the same illness, but with varying viral triggers.

Not everyone agrees.

As well as dispute over long Covid rates (some studies have put the figure much higher), other scientists fear that the "just like flu" interpretation is unhelpful because downplays other post-Covid risks such as blood clots and vascular damage, and overlooks Covid's unique immunological markers. We wouldn't treat all cancers as one disease, for example.

On a more optimistic note, given the similarities, it is possible that by unlocking the causes, cures, and much-need diagnostic tests for long Covid, patients with ME and Lyme disease - who have endured decades of stigma and neglect - could benefit too.

Likewise, rehabilitation services should be offered "to all who need them, irrespective of the initial infection they contracted", said Dr Scott.

She added: "In my own area - the Highlands of Scotland - many people suffer from post-treatment Lyme Disease, which is clinically indistinguishable from long Covid, and yet we are not funded to support them in the same way as we do long Covid patients".

Going by evidence to the Covid inquiries, however, few long Covid patients feel they are getting any help at all.

That has to change - but it should also change for the thousands with other post-viral illnesses, none of which deserve to be minimised.