A record two million people in the UK are estimated to be suffering from long Covid, according to new figures.
Of the two million, 1.4 million said they first had Covid-19 - or suspected they had the virus - at least 12 weeks previously, while 826,000 first had the virus at least a year earlier.
A further 376,000 said they first had Covid-19 at least two years previously.
The figures, from the Office for National Statistics (ONS), are based on self-reported long Covid from a representative sample of people in private households in the four weeks to May 1 2022.
Post-Covid-19 syndrome is defined as signs and symptoms that develop during or after an infection of Covid-19, continue for more than 12 weeks, and are not explained by an alternative diagnosis.
Long Covid is estimated to be adversely affecting the day-to-day activities of 1.4 million people – around seven in 10 of those with self-reported long Covid – with 398,000 saying their ability to undertake day-to-day activities has been “limited a lot”, the ONS found.
Fatigue continues to be the most common symptom (experienced by 55% of those with self-reported long Covid), followed by shortness of breath (32%), a cough (23%) and muscle ache (23%).
Of the two million people with self-reported long Covid, 619,000 – nearly a third – first had the virus, or suspected they had it, during the Omicron period.
The first Omicron wave began in the UK in December 2021 and was followed in March 2022 by another surge of infections driven by the Omicron BA.2 variant.
In contrast, 593,000 people with self-reported long Covid said they first had Covid-19 in the early period of the pandemic, before Alpha became the main variant in late 2020.
Who is most likely to suffer from long Covid?
The ONS said that the rates of long Covid were highest among women, those aged 35 to 69 years, people living in more deprived areas, those working in social care, teaching and education or health care, and those with other health conditions or disabilities.
The figures are based on self-reported long Covid from a representative sample of people in private households in the four weeks to May 1 2022.
What is long Covid?
The long term symptoms can have a profound effect on sufferers' lives.
Long Covid describes a range of symptoms that persist for more than four weeks after being infected with the virus. Symptoms vary but include fatigue, muscle pain and difficulty concentrating, or "brain fog".
From the latest figures, based on self-reporting from a representative sample of people in private households, fatigue continues to be the most common symptom - experienced by 51%.
Loss of smell was the second most common (37%), followed by shortness of breath (36%) and difficulty concentrating (28%).
Other symptoms that have been linked to long Covid include "brain fog", a lack of concentration, mental health problems and even hair loss among some "long haulers". Though there is ongoing research into the condition, one thing medical experts and scientists agree upon is there remains a lot of unknowns even more than two years into the pandemic.
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What are the causes of long Covid?
Experts do yet know for certain, although there are several theories as to the underlying cause of the symptoms.
Dr David Strain, Clinical Senior Lecturer and Honorary Consultant, University of Exeter Medical School, said these theories include the idea of "residual virus 'hiding' in tissues that the immune system cannot easily get to, such as the brain or the gut".
He continued: "This then causes a slow release of chronic inflammation making people feel constantly debilitated. Other theories include an autoimmune reaction, where the body continues to fight itself once it is done fighting the virus; permanent damage done to the mitochondria (The powerhouse of each individual cell), or changes in our immune responsiveness to every day environmental bacteria and viruses.
“There is much yet to learn about this disease, in no small part because previous research into post-viral fatigue syndromes, such as myalgic encephalomyelitis (ME, sometimes known as chronic fatigue syndrome) is far from complete, indeed in some settings woefully inadequate."