'Long Covid' blood clues could prompt future trials

People with "long Covid" have evidence of continuing inflammation in their blood, which could help understanding of the condition and how it may be treated, a UK study suggests.

It found the presence of certain proteins increased the risk of specific symptoms, such as fatigue, in people sick enough to need hospital treatment.

It is unclear whether milder cases of Covid have the same effect on the body.

A test remains a long way off - but the findings may prompt future trials.

Long Covid - symptoms lasting at least 12 weeks after a Covid infection - is thought to have affected millions of people around the world.

Some of the most common symptoms are:

The chances of developing long-term symptoms do not seem linked to how ill people were when first infected - many people who had mild symptoms say they are affected.

And those with long Covid showed evidence of a continuing and active pattern of inflammatory proteins in their blood.

These chemicals appeared when the body fought infection but usually disappeared within six months, the researchers said.

Tracy Evans, 59, from Bridlington, N Yorks, worked as a care assistant and support worker before catching Covid in early 2021.

She spent three months in hospital and six weeks in intensive care.

"I was so close to death, because they were going to turn me off," she says.

Tracy has been unable to work since because of continuing symptoms, including severe fatigue and brain fog.

"Any exertion I am breathless. I'm tired just having a shower or getting dressed. I can't make a bed without people thinking I've run a marathon.

"I'm in pain all the time. Constantly in pain," she says.

When she wrote down her symptoms for a doctor they filled an A4 piece of paper.

"Sometimes with the brain fog, it feels like you've got dementia.

"It's not a life, it's an existence."

The researchers behind the study, in Nature Immunology, also found that some proteins in the blood of those with long Covid could be linked to specific symptoms they were experiencing.

For example, people with gastrointestinal symptoms had increased levels of a marker called SCG3, which has previously been linked to impaired communication between the gut and the brain.

This could help divide long Covid patients into different sub-groups and be useful for designing clinical trials, especially for treatments that target immune responses and inflammation, the researchers said.

Dr Felicity Liew, clinical research fellow from Imperial College London, said the findings indicate that inflammation "could be a common feature of long Covid after hospitalisation, regardless of symptom type".

And this may open the door to drugs which already exist being tried against long Covid, such as those for treating rheumatoid arthritis, an auto-immune condition which causes inflammation of the joints.

Lead research Professor Peter Openshaw said: "This work provides strong evidence that long Covid is caused by post-viral inflammation but shows layers of complexity.

He added: "We hope that our work opens the way to the development of specific tests and treatments for the various types of long Covid and believe that a 'one size fits all' approach to treatment may not work."

The researchers admit they don't know if people who had a mild Covid infection before developing long Covid are also affected by the same immune mechanisms.

They will continue to monitor what happens to the signs of inflammation as time goes by and symptoms improve and disappear, as happens to most people with long Covid.

Dr Liew said she hoped the study would lead to identification of new treatments for the long-lasting symptoms of other illnesses if they were found to affect people in the same way as long Covid.

Prof Eleanor Riley, honorary professor of immunology and infectious disease, at the University of Edinburgh, said the data "should usher in a series of clinical trials for treatment of long-Covid" using several licensed drugs that target inflammation.

She said the study opened up new avenues for the investigation of ME/CFS, which is currently very poorly understood, because many of the symptoms of that condition and long Covid appear to overlap.