What is long covid?

I’ve been getting questions about long covid and my standard answer has been that I don’t think it’s any different from post-viral syndrome, a condition that affects some people after a viral infection but that usually clears up within a few months. I’ve been generally sceptical of claims of long covid as some distinct entity for a couple of reasons.

First, it’s generally impossible to separate out cause and effect from anecdote and observational data. If you have a respiratory infection and then you continue to feel tired afterwards, was it the respiratory infection that caused it or something else? Was it really after the infection that you started to feel more tired, or had you been feeling tired for an extended period of time, but the infection gave you something convenient to blame it on?

To me, long covid has felt a lot like amalgam poisoning, electricity allergy, and chronic Lyme disease – i.e. conditions that some people diagnose themselves with (doctors rarely diagnose them), but for which there are no diagnostic tests, and for which there is no scientific evidence. In other words, I’m inclined to think of it as a phantom condition that is used in place of the real explanation for how a person feels, whether that be depression, an anxiety disorder, sleep problems, alcohol abuse, or something else. For those who have been seriously sick with covid and required intensive care, PTSD is also something that could easily be misinterpreted as long covid (PTSD is actually quite common after intensive care, affecting one in ten patients). Apart from that, some studies have found that almost 60% of people treated in intensive care (for any condition, not covid specifically) still have cognitive impairments twelve months after being discharged – obviously, if you’ve had covid you’ll tend to attribute that to “long covid”, when it is actually a consequence of severe illness and ICU treatment more generally.

Second, covid is not some magical entity, it’s a coronavirus, and it behaves like other coronaviruses, and other respiratory viruses more generally. It would be strange for covid to cause symptoms that other respiratory viruses don’t. And since I’ve never heard of “long rhinovirus” or “long influenza”, I’m inherently doubtful of claims that there’s such a thing as “long covid”. That being said, I understand why patients might want to diagnose themselves with long covid, and why media might want to write articles about long covid.

One thing that is clear about long covid is that it is a social media phenomenon. The disease wasn’t discovered by doctors or scientists. It was “discovered” by people who found each other on the internet. In that sense, it shares something very much in common with conditions that most doctors agree are bogus, but for which there are aggressive patient advocacy groups, such as the aforementioned amalgam poisoning, electricity allergy, and chronic Lyme disease.

But maybe I’m just letting my biases get in the way. So, I decided to try to see what the published literature had to say about covid. That turned out to be easier said than done. My Pubmed search for “long covid” didn’t generate a single article. My searches on Google scholar and medRxiv did generate a few hits, although most turned out to be opinion pieces, not scientific research. There were a few studies of interest though, which I will spend the rest of this article discussing.

The British National Institute of Health Research organized a focus group earlier this year with members of the “Long covid” Facebook group, and the results were published in October. Members of the focus group described symptoms “moving around their bodies” and “coming and going”, and described pretty much all different types of symptoms from every different organ. Even symptoms from the urinary tract were identified as symptoms of long covid.

To me, this is clear evidence that long covid is not one thing, but rather many different things. It’s basically whatever the person who thinks they have it says it is. Anything and everything can be attributed to long covid. Here is a quote from the study, by a woman who has diagnosed herself with long covid:

My journey with Covid19 began on 27th April. I’m still unwell five months on and haven’t been able to resume a normal life since. My worst and scariest experience with this illness was in week 6, when I was rushed to A&E as I had a sudden relapse of symptoms and found myself gasping for air, with the top of my head numb and tingling and a headache so blinding that I couldn’t keep my eyes open. I got worse in the hospital and was shaking visibly, so much so that the nurse couldn’t perform an ECG as I just couldn’t stay still.
Despite having been diagnosed with suspected Covid by my GP and a doctor in a Covid clinic (swab testing wasn’t available to the public at the time) and told I had pleurisy during a visit to A&E two weeks earlier, the doctor on duty didn’t take this into account. Instead, he dismissed me with anxiety, advising a course of anti-depressants, and chose not to investigate these concerning symptoms further. Of course I was anxious, but that was a consequence of the physical symptoms, not the cause!

To me (and I suspect other doctors reading this) it is pretty obvious that the woman was having a panic attack, which the doctor in A&E diagnosed correctly. But she is completely certain that what she had was a “long covid” attack, even though, as is clear from the text, it isn’t even certain that she ever had covid in the first place.

On MedRxiv, there is a pre-print awaiting peer review of a prospective cohort study that followed 4,182 people with positive PCR tests for covid over the course of a few months, to see what symptoms they had, and how quickly they recovered. Participants reported their symptoms in a phone based app.

So, how fast did people recover from covid? 86% had completely recovered within four weeks. At the eight week mark, that number had increased to 95% and by twelve weeks 98% said that they had recovered fully. So, if we assume that this study was reasonably accurate, then one in 50 people who get covid still have symptoms at the twelve week point, at least according to their self-estimation. Unfortunately the study didn’t go on longer than that – it would have been interesting to see how many still felt they had symptoms at the six month mark, to really get an estimate of what the prevalence of long covid is.

The most common symptoms in people with long covid (defined in the study as still having symptoms after four weeks) were fatigue (98%) and intermittent headache (91%). These are both extremely unspecific symptoms, i.e. there is nothing about them that is specific for covid. I’ve had a couple of headaches personally in the last month, probably due to excessive caffein consumption and sharing a home with two screaming toddlers. If I thought I had long covid, I might have attributed the headaches to that instead.

So, what can we conclude from this study?

First, long covid is rare. Around one in fifty people still have symptoms at the twelve week mark, and since the number with symptoms dropped significantly at one, two, and three months, it is likely that the reduction continues after twelve weeks, and that it is a tiny fraction who still have symptoms at six months.

Apart from that, symptoms of long covid are extremely unspecific, so it is probable that long covid is actually a whole bunch of different things, of which I would think post-viral syndrome is likely a significant part. Considering the media fear-mongering going on during virtually all of 2020, I wouldn’t be surprised if many of the so called long covid cases are actually suffering from an anxiety disorder that has been exacerbated by the media response to the virus.

I’m going to finish up by discussing another pre-print currently up on medRxiv. This was another cohort study in which 201 individuals with continuing symptoms four months after infection underwent an MRI of the chest and abdomen to see if there were any signs of “organ impairment”. Now, this study has so many problems that I seriously debated with myself whether to bother writing about it, but for the sake of completeness I decided in favor, especially since it is the only study so far that could be claimed to provide hard evidence for long covid as a distinct entity. If nothing else it will provide a good education in how to use the mantle of “science” to manipulate people so that you can sell more product.

The study was funded by the National Consortium of Intelligent Medical Imaging (NCIMI), which sounds very progressive and nice. This organization is of course in turn funded by multiple companies involved in producing MRI machines, such as General Electric, Alliance Medical, and Perspectum. As it happens, one of the authors of the paper is the CEO of Perspectum. I’m sure you can see where I am going with this. The study was run by people with a strong financial interest in getting hospitals to increase their use of MRI machines. What better way to do that than to “find” a bunch of damaged organs, which no-one would have ever known about if not for MRI?

Ok, so, what they did was this. They got 201 patients who had been diagnosed with covid, either through a positive PCR test, or a positive antibody test, or by having two clinicians independently decide that they had covid, and who still had symptoms at four months. As an aside, those must have been some pretty incredible clinicians, considering that there are no symptoms that are specific for covid, as distinct from other respiratory viral infections. The average age of the participants was 44 years.

The researchers then shoved the patients (metaphorically, not literally) in to an MRI scanner, and scanned their lungs, heart, liver, kidneys, pancreas, and spleen. They then analyzed the images, and compared them with standardized “healthy” reference values. What did they find?

32% of participants had signs of impaired heart function. 33% had signs of impaired lung function. 12% had signs of impaired kidney function. 10% had signs of impaired liver function. 17% had signs of impaired pancreas function. And 6% had signs of impaired spleen function. Overall, 66% of participants had signs of organ dysfunction in at least one organ.

That sounds pretty awful. So what is the catch?

The catch is that they didn’t compare the patients to a control group. This is a standard trick when you want to make something seem really bad, since readers will naturally assume that if there had been a control group then 0% in the control group would have had signs of impaired organ function. And 32% with signs of a heart disorder on MRI is a lot more than 0% .

However, that is actually extremely unlikely. For all we know, more people would have had signs of impaired heart function in the control group than in the long covid group. Since this study didn’t include a control group, it doesn’t tell us anything. The study is useless.

And, as an aside, the study found no correlation between the symptoms the patients had and the findings on MRI. So, double useless. The MRI findings were completely incidental.

So, that pretty much sums it up. There is no hard evidence to support long covid as a distinct disease entity, and the wildly varying, non-specific, and intermittent symptom picture suggests it is actually a conglomerate diagnosis that is being used to describe a large number of different disease entities, and which is being used by politicians and the media in an attempt to scare the hell out of people. Regardless, 98% of people with covid have recovered fully within three months.

Maybe it will turn out that long covid is a real entity after all (distinct from post-viral syndrome, PTSD, anxiety disorder, and so on) when better research is done down the line, but we can’t just assume it based on anecdote, fear-mongering, groupthink, and low quality science. That doesn’t benefit anyone, least of all people with other underlying health issues that are not properly investigated because it’s so easy to just blame everything on covid.

You might also be interested in my article about how accurate the covid tests are, or my article about how deadly covid is.

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Author: Sebastian Rushworth, M.D.

I am a practicing physician in Stockholm, Sweden. My main interests are evidence based medicine, medical ethics, and medical history. I frequently get asked questions by my patients about health, diet, exercise, supplements, and medications. The purpose of this blog is to try to understand what the science says and to translate it in to a format that non-scientists can understand.

47 thoughts on “What is long covid?”

  1. A friend of mine tried to convince me of those draconian lockdowns by argueing that “well but long covid is a real danger…we need to stop every infection we can”. I looked online and found either individual stories from old and already sick people who went through ICU or a bunch of unspecific symptoms.

    One could argue the same with “long lockdown”…since lockdown I feel more tired, have headaches, mood swings and digestive issues. Of course I also now have toddler around 24/7, a wife who needs space for home office and I can’t visit my friends or go out. Therefore I wonder how many people suffer from these unspecific symptoms exactly because of lockdowns and the media panic but those who actually had COVID19 can at least attribute it to their infections while everyone else just calls it “stress”.

    I wonder when we decided that this coronavirus is different from all the other coronaviruses (or related respiratory viruses). Should scientists not assume that this virus will be similar to others we already know about and not attribute daily new dangers to it without any solid evidence?

    Thanks for providing such a clear perspective on the issue.

  2. I had a ‘head-cold’ in Feb 2020 with novel symptoms. About a score of symptoms followed, to the present time. I too concluded it’s ‘post viral’ reaction (I’m 83) and my online researches confirm. Many thanks for your article. Pity BBC cahoots with ‘Them’.

  3. These anecdotal self-diagnoses of long covid resemble pretty much the way believers ascribe curative properties to bogus therapies, such as homeopathy, acupuncture etc. It is never too much to be reminded that “correlation is not causation”

    Your posts are brilliant. Keep up with the good work!

  4. Many thanks for another clarifying article about what I call „the so far biggest market cornering of the century“. The financial markets use that term when some people create a condition by making a product so rare, that the public cannot do anything but pay the price that is demanded. In the past this has been seen with Tulips, Gold, Sugar, Oil, Salmon, etc.
    Today, I have the impression that we see the very same in the medical world: a virus comes around, the medical impact is being blown up to the effect that it destroys economies and many people‘s existences, the used tests are producing a lot of false positives, the created panice makes that any rumour about mortality and other impacts on health is being taken for real, and here comes the vaccine which will solve the problem within 2 years and at an incredible cost for everybody. The guys who cornered the „market“ in this case can only be the pharmaceuticals, because they are the only ones who will benefit.

  5. Your review reminded me of my own experience some 5 years ago when I was diagnosed with prostate cancer. I was lucky enough to be seen by a specialist who was involved in conducting some research into a new form of radiotherapy and was offered the chance to take part in a trial – essentially precision imaging of the tumour and then equally precise targeting of the tumour with a higher intensity dose than normal with the radiation directed to avoid collateral damage. It was very successful.
    As part of the study I underwent a whole range of scans including a whole body PET scan. I recall while talking to the consultant after it that she said that the PET scan had picked up a number of issues but they wouldn’t go into them at the time and would concentrate on the task in hand.
    I have never found out what these other issues were, and I assume (hope) that if they were important then they would have followed up. I remain a comparatively fit, if a little overweight, in my mid 70s, but nevertheless they had spotted something which they thought worthy of comment but which doesn’t appear to have affected my life.

  6. I remember a German doctor who works in a rehabilitation clinic, reporting about “long Covid” on a talkshow together with politicians as well as one “Covid-critic”, and she used just the descriptions you mention in this article. To me, it sounded much like conditions previously called “chronic fatigue”, “borreliosis”, “burn-out syndrome”, PTSD or other syndromes in the category “we don’t know really”. But here, politicians seem to use these types of unspecific long-term dis-ease and attach them to Covid for their purpose of keeping citizens in a highly alert state, justifying the “better safe than sorry” narrative and quite draconic containment measures.
    Thank you for commenting the studies out there, whether this can be backed up by replicable findings.

  7. As a non-scientist but as someone who has observed post-viral lassitude in friends in the past (sometimes lasting months) your reflections on long covid match my own. The section at the end about MR scanning was rightly cynical and funny -many thanks for your posts.

    -Bill

  8. Whilst I am also of the opinion that “long-Covid” is probably no different from “post-viral fatigue syndrome” and other such conditions that follow many viral infections (often glandular fever, in my experience) I wondered if you had watched the BBC TV programme by the UK doctors Xander and Chris Van Tulleken?

    One of them, Dr Xand, contracted Covid-19 whilst working in a care home in the early days of the outbreak and after having “recovered”, a few days later developed atrial fibrillation necessitating him to have his heart stopped and restarted. He attended a specialist physiotherapy centre as part of his post-recovery surveillance and was told that since Covid had appeared, they had had a lot of patients attending with unusual symptoms.

    Here’s the TV programme – https://www.youtube.com/watch?v=1wPmds8W5pc

    So is it real, is it a “new thing” or what?

  9. You write: “Second, covid is not some magical entity, it’s a coronavirus, and it behaves like other coronaviruses, and other respiratory viruses more generally. It would be strange for covid to cause symptoms that other respiratory viruses don’t.”

  10. Could you maybe expand a bit on the long term effects that were observed in patients diagnosed with Mers and Sars? It seems that the long-term effects were very pronounced. 30 percent of those recovered severere Sars or Mers had still long-term long abnormalities, and 40 percent recovered from Sars still had chronic fatigue after 3.5 years later. See: https://www.medicalnewstoday.com/articles/long-term-effects-of-coronavirus#what-we-know with a reference to these studies:
    https://www.bmj.com/content/370/bmj.m3001 and https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/415378

    Is what we are seeing now with the “long haul” Covid patients not exactly what we would expect given the lung abnormalities and chronic fatigue in Sars and Mers patients? Is the parallel with Sars and Mers not an indication we should take long covid seriously as a possibility?

    1. Hi Penelopeia,
      The big difference is that SARS and MERS are much more severe diseases than covid. As I mention in the article, it is not uncommon for people to have lingering symptoms after a severe illness, specially if it was so serious that they ended up in the ICU. The difference with covid is that even people with mild illness are saying that they have long covid, which means it is something different.

  11. Thank you for your article. Aside from “long covid”, my parents (very healthy and 72 years old) are worried about the seriousness (aside from death) of getting infected with SARS-CoV-2. I know it is much more serious (deadly?) for the elderly than for children, and maybe there is something to that. Is there some perspective you can give to set their minds at ease? They are so worried!

  12. Dr. Rushworth– Is it possible to have had a relatively mild case of MERS and this resulted in some sort of protection against covid? The reason I ask, is that I was based in Saudi Arabia in 2012 and got sick with a respiratory illness that laid me up in the hotel for about a week and then was feeling kind of worn out for a week or so after that.

    For various reasons, I have had 11 covid tests–all negative. But, it has dawned on me I have not been sick once with anything respiratory since that episode in SA in 2012.

  13. Could some of the long Covid people actually have symptoms of vitamin D deficiency? Symptoms of vitamin D deficiency can include muscle weakness, bone and joint pain, hair loss, headaches and fatigue. Staying inside and getting insufficient sunlight during lockdown would be enough to cause this and the infection itself might reduce vitamin D levels.

  14. Your comment about vitamin D deficiency got me thinking, because I’ve heard many medical people describe the symptoms of serious Covid-19 resembling a severe vitamin C deficiency too, like “scurvy”. It wouldn’t be a surprise being as the body uses up so much vitamin C when fighting a viral infection, and possibly a chronic deficiency of vitamin C in the diet might be responsible for various odd symptoms that continue or appear following apparent recovery. Or maybe other micronutrients too?

  15. Dear Sebastian
    I asked my other source of trustworthy info, swprs.org, about „long covid“. They seem convinced, that this is an existing and severe condition.

    They directed me to the following website (in swedish):
    https://novus.se/novus-coronastatus/

    Would you care to comment?

    Thank you for all the interesting information.

    LG 🙂 Thomas

  16. Is this the same sort of thinking which was thrown at Florence Nightingale for decades, when in fact she most likely did have “Long Brucella militensis”?

    During those decades, the medical people told her she was malingering – was in her head and stress and anxiety-induced neurosis.

    I think more caution is required, because we know that all viruses can induce a form of “long-something” in some people…..

    https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2539100/pdf/bmj00624-0051.pdf

  17. Hi thedullchannel, I think it is established that lethality of SARS-CoV-2 is less than SARS-CoV-1 and, certainly, less than MERS. Which, as far as I understand it, explains why Covid-19 has spread. It can infect many organisms that don´t die.

  18. Interesting article, well put together and argued, except for the somewhat bizarre decision to include Lyme disease in with the so-called “self-diagnosed” illnesses? We know what Lyme is, we know the underlying cause, and we understand why it can effect the body in a large number of different ways (especially when left initially undiagnosed/treated).

    1. Yes, acute Lyme disease is a real condition and if untreated, Lyme disease can last a long time. Chronic Lyme disease is a distinct condition, in which people claim to have ongoing symptoms due to Lyme disease in spite of antibiotic treatment and in spite of not having any bacteria in the body, or any organ damage that could explain the symptoms. It is widely agreed among doctors that chronic Lyme disease does not exist.

  19. What about parosmia? I know a healthy young woman who had a very mild case of COVID and it now suffering from a case of parosmia, which makes everything smell and consequently taste like rotting garbage. I would be interested in your thoughts on this. She is not alone – there are a lot of reports of people with this after effect – and nobody knows how long it will last.

  20. I have read about a number of people who’ve had this since March, with no sign of a letup. It seems much more prevalent with Covid than with others viruses. It is also hell to live with. Most doctors seem unaware of parosmia especially and just say “it will pass”. Small comfort to those who are suffering.

    1. I understand that it is small comfort. But it does usually improve, at least after other viral infections, and there is no reason to think covid is different. The olfactory nerves are able to regenerate after being harmed.

      I think the difference with covid is entirely due to the fact that covid is a new virus, so there was no underlying population immunity and therefore a lot of people became infected at the same time. That doesn’t mean the risk is any higher for any one individual that gets infected than it would be with another virus.

  21. Dear Sebastian,

    I found a paper from Reuters saying that “Sweden registered 96 new deaths among people diagnosed with COVID-19 on Wednesday, the highest for at least three months, Health Agency statistics showed.” Is it the death toll for one day?

  22. Hi Sebastian, thanks again for another sensible opinion.
    Of course , you hit the nail on the head, long covid is a social media phenomenon.
    But, just like Chronic Fatigue Syndrome, Chronic Lyme Disease, (and you forgot Morgellon’s disease), these invented pseudo diseases will sprout many patient advocate groups, blogs from sufferers, and support groups which will lobby governments for money and support. Once again, doctors will be the bad guys “who just don’t believe me”, but the naturopaths , homeopaths and iridologists will happily take their money.
    There’s truly “nothing new under the sun”.

    1. Hi Marquinhos,
      I’ve looked at the study now. It is of people who were seriously sick with covid, so sick that they required hospitalization. 36% spent time in ICU. It is thus not representative of the average person with long covid.

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