What is long Covid and why are people having symptoms for months?

At the beginning of the pandemic, the government believed the long-term impact of the virus was similar to known respiratory illnesses, like the flu. But it soon became clear that coronavirus operates differently, which is why they adopted a flu pandemic model.

In the latest figures, the Office for National Statistics released data showing that long Covid is limiting the ability of 1.2 million people in the UK to undertake day-to-day activities.

The long-term impacts of coronavirus are increasingly noted by experts and survivors. A December 2021 study found that less than three in 10 patients admitted to hospital with Covid reported they felt fully recovered one year after recovery.

So what is long Covid and why does it happen to some patients and not others?

The NHS describes long Covid as the lasting symptoms of the virus that remain after the infection is gone.

Sufferers report a huge spectrum of problems beyond the 12 NHS Covid symptoms (including persistent cough, fever, headaches, aching muscles and loss of taste or smell). These include fatigue, breathlessness, 'brain fog,' memory loss, lack of concentration, and depression. It is not thought that people are infectious for the long period, but just suffer long-term effects.

Although the term is still colloquial rather than universally medically-approved – several celebrities including actors Alyssa Milano and Emma Samms have shared experience of issues like hair loss – there is increasing scientific evidence to support the idea of a long illness.

The Zoe Covid study estimates that 1-5 per cent of people who get Covid experience debilitating symptoms, to the point where they can’t carry out their usual activities, for 12 weeks or more.

Additionally, research from Italy published in the Journal of the American Medical Association, reported that nearly nine in 10 patients (87 per cent) discharged from a hospital in Rome were still experiencing at least one symptom 60 days after onset.

They found that 13 per cent of the 143 people were completely free of any symptoms, while 32 per cent had one or two symptoms, and 55 per cent had three or more.

The Royal College of General Practitioners said it expects GPs to see an influx of patients with "lingering" illnesses but there is less certainty as to why some people suffer for longer.

A 2020 report from King’s College London suggested that those with longer-term symptoms could be related to the severity: “Evidence is mounting that some people who have had relatively mild symptoms at home may also have a prolonged illness.

“Although we know that lasting fatigue can sometimes follow other viral infections, detailed mechanistic insight is, for the most part, lacking. An ongoing viral infection in lung, brain, fat or other tissue may be one mechanism. A prolonged and inappropriate immune response after the infection has been cleared might be another."

And a previous study into post-illness chronic fatigue showed that some patients may just be biologically predisposed to such a response. "When a chemical called interferon-alpha was given to people as a treatment for hepatitis C, it generated a flu-like illness in many patients and post-viral fatigue in a few.

Researchers have studied this “artificial infection response” as a model of chronic fatigue. They found that baseline levels of two molecules in the body that promote inflammation – interleukin-6 and interleukin-10 – predicted people’s subsequent development of chronic fatigue, said the report.

Patients in hospital with coronavirus should be offered a follow-up as early as four weeks after developing the illness to check for symptoms of long-Covid.

Guidance drawn up by health officials across the UK states that the long-term effects of the virus can be “significant”.

The guidelines were developed collaboratively by the National Institute for Health and Care Excellence (NICE), the Scottish Intercollegiate Guidelines Network (SIGN) and the Royal College of General Practitioners (RCGP).

The NHS has also launched a Covid-19 rehab service. Your Covid Recovery Service, for people who have been suffering with the long-term effects of the virus.

Anyone concerned about their symptoms, or who would like to be referred to the service should contact their GP.

Your doctor should offer an initial consultation and provide access to any further assessments for care.