What Is Long COVID? Definitions From Health Authorities
Long COVID is the name commonly given to symptoms that continue, or appear, after an infection with the virus that causes COVID-19 and that cannot be explained by another diagnosis. Health bodies use slightly different wording and time limits, but they agree on the core idea: some people do not return to their usual health within the first few weeks. The condition is also called post-COVID condition or post-COVID-19 syndrome.
How the main bodies define it
The definitions differ in the time they require, which is why you may see different figures quoted.
| Body | Wording in brief |
|---|---|
| World Health Organization | Post-COVID-19 condition: occurs in people with a history of probable or confirmed infection, usually three months from onset, with symptoms lasting at least two months that cannot be explained by another diagnosis |
| NHS England / NICE guidance | Signs and symptoms that continue or develop after acute COVID-19; “ongoing symptomatic COVID-19” is used for 4 to 12 weeks, and “post-COVID-19 syndrome” for 12 weeks or more |
| US CDC | Broadly, signs, symptoms and conditions that continue or develop after COVID-19 infection; the CDC’s own pages give the current wording and time frame |
| US National Academies of Sciences, Engineering, and Medicine | An infection-associated chronic condition, present for at least three months, which can be continuous, relapsing and remitting, or progressive, and may affect one or more organ systems |
The WHO definition came out of a consensus process published in 2021. Definitions continue to be reviewed as research develops, so always check the current text from the source itself. The WHO publishes a fact sheet on the post COVID-19 condition, and the NHS has a page on long COVID.
Commonly reported symptoms
Long COVID is not a single set of symptoms. People report a wide range, and the pattern can differ from one person to another. Frequently described symptoms include:
- Extreme tiredness (fatigue)
- Shortness of breath
- Problems with memory and concentration, often called “brain fog”
- Difficulty sleeping
- Heart palpitations or a racing heart
- Joint and muscle pain
- Headaches, dizziness and pins and needles
- Changes in smell or taste
- Low mood and anxiety
Symptoms can come and go, change over time or get worse after physical or mental effort. Because many of these symptoms have other possible causes, a doctor will usually consider and rule out other explanations.
Who can be affected
Research suggests that long COVID can follow infections of any severity, including mild ones, and can affect children and adults. How common it is varies between studies because of differences in definitions, populations and the time since infection. For that reason, no single percentage in this article should be taken as definitive; national health statistics offices and the WHO publish figures with explanations of how they were gathered.
How it differs from recovering slowly
Many people take weeks to feel normal after an infection, and that is common with many viral illnesses. What marks long COVID in the definitions above is the persistence of symptoms beyond the expected recovery period, or the appearance of new ones, without another explanation. The line between slow recovery and long COVID is not sharp, which is one reason doctors look at the pattern over time and not at a single visit. Keeping a short note of symptoms, their timing and what makes them better or worse can help that conversation.
What is not yet settled
Researchers are still investigating the causes. Hypotheses studied include persistent virus or viral fragments, immune system changes, effects on blood vessels and the nervous system, and the impact of the original illness on other conditions. There is no single diagnostic test for long COVID, and evidence about treatments is still developing. Anyone offering a guaranteed cure should be treated with caution, and personal treatment decisions belong with a qualified clinician.
Getting help
In the United Kingdom, people with symptoms that last beyond several weeks are generally advised to contact their GP, who can arrange tests and, where appropriate, refer to a specialist long COVID service. Other countries have their own routes, so check your national health service. Seek urgent medical help for severe breathlessness, chest pain, confusion or other symptoms that feel alarming.
Frequently asked questions
How long does long COVID last?
It varies. Some people improve within months, while others have symptoms that continue for longer. Health bodies use three months as a common marker, but that is a definition, not a limit.
Is long COVID the same as post-viral fatigue?
They overlap, and some symptoms are similar. Researchers are comparing long COVID with other post-infection conditions, but the relationship is still being studied.
Can you get long COVID after a mild infection?
Yes, studies have reported it after mild illness as well as severe.
Is there a test for long COVID?
No single test confirms it. Doctors typically take a history, examine the patient and run tests to look for other causes.
The site’s home page gives context on the topic, the press page lists media coverage and the blog contains a personal diary in several parts. Personal accounts are not medical guidance. For advice about your own health, speak to a doctor or other qualified health professional.