LONG Covid has baffled scientists more than the virus itself.

Millions of people are grappling with long-term effects of Covid illness, sometimes with no answers for how to relive their symptoms.

In the UK, an estimated 1.3 million people – one in 50 – are likely to be suffering from long Covid.

The figures from the Office for National Statistics, collected in the month to December 6, suggests rates of long Covid are the highest they have ever been.

Some 809,000 people said long Covid adversely affected their day-to-day activities. 

Fatigue is the most commonly reported symptom (51 per cent), followed by loss of smell (37 per cent) shortness of breath (36 per cent) and difficulty concentrating (28 per cent).

Now, scientists led by the Institute for Systems Biology, Seattle, Washington, say they have been able to pinpoint four key factors that may help predict who will end up with the condition.

These can be identified at the original point of Covid diagnosis.

They are:

• Type 2 diabetes
• High viral load
• Reactivation of EBV virus
• Autoantibodies 

The researchers called these “PASC factors”, as long Covid can sometimes be referred to as Post Acute Sequelae of Covid-19 (PASC).

Dr Jim Heath, co-corresponding author of a research paper and president at ISB, said: “Identifying these PASC factors is a major step forward.

"Not only understanding long COVID and potentially treating it, but also which patients are at highest risk for the development of chronic conditions.”

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Previously, a study found having five or more symptoms in the first week of coronavirus infection could forecast a longer-lasting battle with long Covid.

And data from the Covid Symptom Study app has found obesity, asthma, older age and being female are risk factors.

The Office for National Statistics has found long Covid is most common in women and Brits; aged 35 to 69 years, living in poor areas, working in health and social care and with a disability.

Detecting markers

The team in Seattle collected blood and swab samples from 309 Covid patients to investigate common features in those who had lasting problems of the virus.

The first thing they discovered was that viral load was “strongly associated with certain long Covid symptoms” months later, said Dr Yapeng Su, a co-first and co-corresponding author of the paper. 

Viral load can be measured when someone first gets sick with Covid. It’s the total amount of virus in a person’s body.

Secondly, researchers found the Epstein-Barr virus (EBV) is reactivated early on after Covid, which is significantly associated with future long COVID symptoms.

EBV is a common virus that most people catch when they are a child, causing symptoms for around two weeks. 

The virus becomes inactive in the body but can sometimes reactivate, with triggers including stress, the menopause or hormonal changes.

Dr Su said EBV may be reactivated in Covid patients due to a malfunction of the immune system, called “immune dysregulation”.

The third factor implicated in long Covid appears to be pre existing type 2 diabetes – a condition that around 3.7 million people in the UK live with.

The researchers did not offer an explanation for why this might be. 

Already, it’s clear that those with diabetes are at a higher risk of serious Covid complications, as they are with other viruses.  

Lastly, the researchers found that when people had higher levels of autoantibodies, they had lower levels of protective Covid antibodies.

Antibodies are proteins of the immune system that attack pathogens, like Covid. 

But autoantibodies, on the other hand, are those that recognise and attack parts of our own body by mistake. 

Their presence in the body may cause sickness as healthy tissues are damaged.

Previously researchers at Cedars-Sinai Medical Center found that autoantibodies produced by Covid patients may last for six months.

These proteins are “usually linked to chronic inflammation and injury involving specific organ systems and tissues such as the joints, skin and nervous system”, the team said.

What’s more, the researchers of this new study said high autoantibodies and low Covid antibodies may make some more susceptible to catching the virus again.

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