Long CoVid: is it different from the long term effects after flu?

8 March 2021

As the concerns about the life-threatening risks from CoVid-19 are beginning to recede, so there is growing interest in the long-term effects following infection.  Whereas it might be expected that those who had suffered severe complications and been hospitalised would have continuing health issues, the concern now is that those with mild, or even asymptomatic, infection would have continuing symptoms over several months.  In this post I consider the evidence. 

Before Covid-19……

This banner headline from Medical News Today was from an article written in October 2019  just before the pandemic (how coincidental was that!)

  • It acts as a reminder that following the recovery from the acute stage after any viral infection, a proportion of patients continue with symptoms, most specifically:
    • Fatigue
    • Lack of energy
    • ‘Brain fog’ 
  • Post-viral fatigue/syndrome was a helpful term in describing this experience
  • The relationship with a prior viral infection is not clear, as many suffer the same symptoms without evidence of a proven prior virus  – leading to the non-specific term chronic fatigue syndrome (CFS) *
  • The proportion of people who have continuing symptoms, following flu for example,  does vary between reports – depending on how the cases were recruited – but there is no debate that the continuing fatigue can occur in some people and last for a long time
  • A more potent viral infection causing long-term fatigue is glandular fever (infectious mononucleosis).  This infection has a predilection for young people and many students have had their university courses seriously affected by the long-term effects following this 

*I do not wish to get into the debate about the name ME – myalgic encephalomyelitis – just to say that I do not find it helpful as whilst the ‘myalgic’ bit, meaning muscle ache, may be descriptive, the ‘encephalomyelitis’ term is misleading – and should be reserved for the specific and severe acute brain infection, which is exceptionally rare in individuals with CFS 

Theories about the cause of post viral fatigue

  • There are many theories and this post is not the place to discuss the hundreds of studies that have proposed or disproved various biological explanations
  • Of relevance to Long CoVid is the observation in some studies that it is the body’s own immune system that goes into overdrive in some people, that explains the continuation of symptoms

What is Long CoVid?

  • It is one thing to say that some people have continuing symptoms, it is another to have a definition that can be used as a label
  • That’s important as it is impossible for example to compare between studies, or to consider who should have specific treatments, unless there is a common rule for saying ‘this is a case of Long CoVid’
  • The problem is there is no simple agreed definition:
    • The UK’s: National Institute for Health and Clinical Excellence – NICE- came up with this scheme which separates out short-term and longer-term problems
    • How useful they are is debated and not agreed internationally
  • At the moment therefore, rather than use Long CoVid as a term describing a specific focused disorder, it is used as an umbrella term to cover all the people with continuing problems
  • Thus, the focus has been on attempting to identify how often this happens, what are the symptoms and who is at risk 

How often do symptoms persist?

  • As mentioned at the beginning of this post, the key question for me is not about the continuation of symptoms in people who have been in hospital, but what happens to people in the community who have been tested positive
  • I am going to give the results of the UK’s population survey (Office of National Statistics – ONS study) which followed up 9063 people between April and December last year, who had tested positive in their ongoing population surveys to find out if they were unwell at 5 and then 12 weeks after the positive test.
  • They asked about 5 symptoms:
    • Fatigue
    • Cough
    • Headache
    • Loss of taste and smell
    • Muscle aches
  • This what they found in terms of one or more of these  symptoms:
  • A word of caution of course: these are common symptoms, even without the virus. Thus the people in the ONS survey who tested negative for CoVid-19 may have had the same symptoms but they were not followed up.
  • The ZOE-Kings College App, used by millions in the UK and USA, has been tracking symptoms in people with and without CoVid-19 to provide a suitable comparison 
    • People were asked about symptoms 28 days after a positive test
    • A comparison group (same age, gender etc)  who never tested positive were asked about symptoms at a random time 
    • The CoVid positive group had 6 times the rate of these symptoms

Which specific symptoms persist?

  • The ONS survey showed that most people who reported symptoms had 2 or 3 of the 5 symptoms above, with no single symptom being the more common

What are the risk factors?

  • Role of gender
    • What is a little interesting from the data above is that the rates of reporting were slightly higher in women then in men 
    • Remember it is men who are more likely to be hospitalised from the CoVid
  • Role of age
    • Older people were more likely to report continuing symptoms
    • Unlike the risk of life-threatening complications, the proportion with symptoms did not change that much across the adult age span
  • Also note that children who test positive are not free of long term symptoms Indeed, children commonly report other long-term symptoms including:
    • Sore throats
    • Mood changes (I assume more than normal!)
    • Rashes
  • There are other groups of people who are more at risk of Long CoVid.  These include those who:
    • Are obese
    • Have pre-existing conditions such as asthma
    • Have specific Covid-19 symptoms such as loss of sense of taste and smell

Does it all sound rather minor?

  • At first glance the persistence of these symptoms may be considered, because they are not life threatening, as not too worrisome
  • That of course underplays the impact on individuals of the persistence of feeling unwell
  • There is another side to the Long CoVid story, which is the risk of new serious health problems
  • Although it is difficult to put numbers on what are quite small risks, there are a number of serious late effects with CoVid-19
  • Many of the more serious consequences are thought to be due to blood clots and scarring of major organs including:
    • Lungs
    • Heart
    • Kidneys
    • Liver
    • Gut
    • Brain
  • Plus some patients have reported the development of other diseases associated with the body’s immune system attacking itself
  • Perhaps less expected is the possibility that CoVid-19 could lead to the development of diabetes
  • Although many CoVid-19 patients with new diabetes are those who had been hospitalised with severe infection, this is not always the case
  • I am going to be cautious again though in giving conclusions about these serious consequences – why?
    • The numbers for each of these complications are very small
    • Given the millions affected by CoVid-19, some of these severe problems might have arisen by chance, independent of the CoVid-19 
  • But they should not, and are not, being ignored and more research is ongoing

Why CoVid-19 might be different from other viruses in its long-term complications?

  • Having read thus far, you might feel that I have not made a case that there is an undoubted issue with Long CoVid that is different from the problems people report following flu
  • The numbers of those with continuing disabling symptoms are higher – although the quality of data from other common viruses is poor
  • I am however persuaded that this virus is different because of some special features that I have mentioned in previous blogposts
    • The virus locks onto a protein found on the surfaces of cells of many of our organs called the ACE receptor and this can explain why organs such as the lungs, kidneys and heart could be damaged
    • As part of the body’s response to this virus, the immune system does sometimes go into overdrive – indeed this unwanted response is the cause of many of the deaths of patients in intensive care units
    • This overdrive caused by the body producing too many nasty proteins called cytokines can damage the walls of our small blood vessels, which makes them more likely to allow clots to form

My take home message

  • We need to think about the long-term consequences of CoVid-19 seriously
  • There can be long-term symptoms even in those who had mild infections or even were asymptomatic
  • The overwhelming majority do recover but a significant minority have continuing health challenges to their everyday life for some months
  • This includes people of all ages including children
  • It is difficult to put numbers on the level of these risks and serious long-term effects will still be the exception 
  • The diabetes story is intriguing
  • And my answer to my opening question: I think this is different from the issues seen in recovery from other viruses, especially flu 

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One reply on “Long CoVid: is it different from the long term effects after flu?”

Many thanks.
On a other tack, can you clarify the R number?
I see that there are 11 new cases per 100,000 population in N W and R=1. If R reflects number likely to be infected by each case, wouldn’t one expect R to fall as there are fewer susceptible people following immunisation? It was as low as 0.8 when there were many more new cases per day.


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