How should we define Long Covid?

Part of the UK COVID-19 National Core Studies
conv(1) (1) (4)

Introduction (scroll down down to see latest posts)


The purpose of this discussion is to help develop a working definition of ‘Long COVID’ for the Convalescence Project. The aim of the CONVALESCENCE Project is to improve our understanding of Long-COVID so that we are better able to provide treatment and support.

The CONVALESCENCE team thinks that it is essential that people with experience of Long COVID are involved in developing this definition.

A key question being asked in the study is how do people experiencing Long COVID define it. People experiencing or have experienced Long COVID are essential to this work to make sure nothing significant is missed. It can also help researchers know where to look in search of answers.

This discussion will build on work done with the Project’s Patient Advisory Group.


The term ‘Long COVID’ originated with patients. It is generally used to describe a diverse set of symptoms extending beyond four weeks after symptom onset of COVID-19. Beyond this, there remains a lot of uncertainty.

The reason for this uncertainty is there remains limited understanding of what causes Long COVID, why it affects some people and not others, how if effects people differently, and why some people recover and others have progressive and/or remitting and/or ongoing symptoms. The research is still at an early stage. This uncertainty is problematic as it makes it difficult to provide appropriate advice and guidance, and develop appropriate services and support, for those living with Long COVID.

Defining Long COVID

We are using as the starting point the NICE definition of Long COVID. NICE is the UK’s National Institute for Clinical Excellence. Their aim is to improve health outcomes for people using the NHS and wider health and care services.

As per the NICE definition,

‘the term ‘long COVID’ is commonly used to describe signs and symptoms that continue or develop after acute COVID‑19. It includes both ongoing symptomatic COVID‑19 (from 4 to 12 weeks) and post‑COVID‑19 syndrome (12 weeks or more).’

You can read more about the NICE definition including the distinction between ongoing symptomatic COVID-19 and post-COVID-19 syndrome on page 5 of the COVID-19 rapid guideline: managing the long-term effects of COVID-19.

Input from the Patient Advisory Group

The project’s Patient Advisory Group met in December to have an initial discussion about a definition, or definitions, of Long COVID. Key points coming out of this discussion:

  • Questions about the timeframes used in defining Long COVID;
  • Importance of distinguishing between people who still have Long COVID with no apparent end in sight and those who have recovered;
  • Many of the definitions include reference to Long COVID as a condition that cannot be ‘explained by an alternative diagnosis’. This was considered an important part of the definition;
  • Long COVID symptoms weren’t always consistent with the initial symptoms so reference to ‘ongoing’ symptoms as part of the definition may be a problem;
  • Describing the condition as Post COVID might be useful to imply that it is something different to COVID. Long COVID may suggest that it is an extension of symptoms of the initial infection;
  • Descriptions of COVID as a respiratory condition may be unhelpful. Instead, COVID and Long COVID may sometimes be better thought of as an illness that affects whole systems of the body e.g the immune system. .

Background documents

These are google documents.

Annotated bibliography on definitions of Long COVID - for comment

Defining Long COVID - Discussion paper for Patient Advisory Group (Dec 2021) - for information

Defining Long COVID - Note of meeting of the Patient Advisory Group (Dec 13 2021) - for information

Defining Long COVID - Note of meeting of the Patient Advisory Group (Feb 7 2022) - for information

It is important that people feel comfortable and share their perspective on this topic.

  • Please be considerate in how you reply to others. Any posts that are deemed offensive by the moderators will be removed.
  • Sharing experience and opinion is valid, sharing facts and information from other sources may also be appropriate. Please be clear about the source of any information you present.
    Please state whether something is your experience, opinion, or share details of any other source of information such as website or video links.
    If claims are made without acknowledging the source of the information the post may be removed. Moderators will endeavour to provide a reply to the post requesting source information is added and provide at least 24 hours to add to / edit the information in the post but there may be situations that posts are removed without a time delay and public request. This is to help ensure that the conversation is kept focused on the question at hand… how should we define Long COVID?

This is a publicly visible forum - please do not share any sensitive information such as name, address, contact details, place of work etc. as the moderators have no control who will see this information. Posts disclosing such information may be removed.

Moderation will be done by the Patient and Public involvement team in the CONVALESCENCE project.

Some of you may have seen over the weekend some interesting new research on hidden lung damage caused by COVID 19 infection. See Long Covid: Hidden lung damage spotted on scans - BBC News

In terms of a definition it makes me think that it is important to distinguish between illness and symptoms caused by the infection (which in some people may take a longer time to clear) and symptoms or damage that persists post the COVID infection. Symptoms due to ‘damage’ and may be different to the ones initially caused by the infection. I’d be interested to hear what others think…

@Beaky has put this post in a different topic forum… I am copying into this conversation because it is relevant…

(Thank you @Beaky)

And here is a post from @Citizen689:

Thanks for your posts. Do you think it is worth distinguishing between different types of Long-COVID. There may be a wide range of symptoms with different causes that all get lumped together as long COVID

An interesting thought Andy. How do we determine between symptoms caused by the infection and symptoms due to damage? Many of us are a long way down the line now and have had tests (x-rays, CT scans) that show nothing - this new test sounds promising.

One approach could be to make the definition of long COVID begin later. The following was given in a paper published yesterday looking at young people. "Post-COVID-19 condition occurs in young people with a history of confirmed SARS CoV-2 infection, with at least one persisting physical symptom for a minimum duration of 12 weeks after initial testing that cannot be explained by an alternative diagnosis. The symptoms have an impact on everyday functioning, may continue or develop after COVID-19 infection, and may fluctuate or relapse over time. NB . This is a research definition rather than a clinical definition, i.e. in research it is important to be clear, beyond reasonable doubt, who does and does not have COVID-19 when making comparisons, hence the insistence on a positive test result, but leaving that aside I’d be interested in what you an others think of this definition.

FYI, the the study is here for anyone interested.
Archives of Disease in Childhood- Delphi consensus - Defining long COVID in children (002).pdf (1.3 MB)

I think the Diseases in Childhood definition is the best we’ve seen so far. It includes all the relevant points and I like the fact it does mention the impact symptoms have on everyday life which we haven’t brought into previous definitions. I’m wondering whether it’s time to move away from ‘Long’ and use ‘Post’ to define this condition as ‘Long’ implies an extension of symptoms which may not be the case.

1 Like

I personally think waiting for 12 weeks is too long for a long covid definition. I think it should be 4 weeks and symptom relief slows down by 12 weeks. What if any damage is irreversible by then? I think if we are able to identify and possible treatments to relieve or reverse long covid symptoms then the sooner we can start then the better, both for the sufferer and the economy at large. Do we know where the original 12 weeks came from?I would be interested to know what others think of the 12 week marker?

1 Like

Great points and I’m sure others will have views.

In terms of the 12 weeks, my understanding is that it comes from the World Health Organization’s clinical case definition. This definition was developed through a consensus process carried out globally. They considered the issue of the a minimum time period (in months) from the onset of COVID-19 to the presence of symptoms - the consensus view was 3 months.

It’s worth adding that for WHO, this is the working clinical case definition for now and that it may change as new evidence emerges and our understanding of the consequences of COVID-19 continues to evolve.

You can read more here

And yes, I very much agree with the view of the importance of identification and treatment as soon as possible. A lot of the current research is focused on the diagnosis and treatment of Long COVID, through to rehabilitation and recovery.

There remain a huge number of unknowns including why some people get it and don’t seem to recover, while others do; and why for some, the effects can have a significant impact on everyday life, where for others the impact may be relatively mild; or why symptoms may change over time, and/or can be persistent and/or remitting.

Hopefully the research can answer some of these questions.