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Long Covid symptoms may be driven by the reactivation of dormant viruses such as herpes, scientists have suggested, after finding evidence of inflammation in the blood of sufferers.
At the last count by the Office for National Statistics (ONS) last year, some 1.9 million people reported symptoms of long Covid, which can include fatigue, brain fog and muscle aches.
Now Imperial College and the University of Leicester have found that in long Covid sufferers, the immune system is still active long after a Covid infection has cleared up, with tell-tale signs of inflammatory proteins detectable in the blood.
Experts said this inflammation might be caused by trace amounts of Covid-19 lingering in the body, auto-immunity, in which the immune system attacks the body’s own tissues, or even the reactivation of other viruses.
Dr Felicity Liew, from Imperial’s National Heart & Lung Institute, said: “Even though the acute phase of illness resolves, there may be virus persisting in the body that could continually trigger the immune system and cause the ongoing inflammation that we found.
“It can also cause reactivation of herpes viruses or people that previously had glandular fever caused by Epstein-Barr virus, and it can cause that to reactivate and cause ongoing symptoms.
“Or it can result in autoimmunity, and all of those scenarios result in the types of inflammation that we see, and could result in chronic and ongoing abnormal inflammation represented by these proteins highlighted here.”
Herpes viruses
There are eight herpes viruses that routinely infect humans, and which lie dormant in the body. Around 70 per cent of people in Britain carry the Herpes Simplex type 1 (HS1) virus, which causes cold sores, while 10 per cent have HS2, which can cause genital warts and is linked to cervical cancer.
Similarly, around nine in 10 people carry Epstein-Barr – also a type of herpes – which mostly causes no problems, but can sometimes lead to glandular fever, encephalitis, meningitis and trigger auto-immunity.
Usually dormant viruses are kept at bay by the immune system, but experts think Covid-19 requires so much attention that it may allow other viruses through the defensive cracks.
The new analysis looked at blood plasma from 426 people who had been hospitalised with Covid and had experienced long-term symptoms and compared them to blood from hospitalised people who had not had ongoing problems.
Those with long Covid showed cellular inflammation and activation of a family of immune system proteins called the “complement system”.
The complement system kicks in in response to infection or tissue damage and is known to be associated with many autoimmune and inflammatory conditions.
The research suggests that anti-inflammatory drugs, which help reset the body’s immune system could be helpful in treating long Covid.
Trial into Tocilizumab drug
The University of Leicester is leading a trial into the rheumatoid arthritis drug Tocilizumab, which lowers inflammatory proteins.
Researchers believe long Covid may be similar, or the same, as post-viral syndrome which leads to people experiencing fatigue and brain fog after influenza and other viruses, and may be to blame for conditions such as ME/CFS.
The team say the sheer number of people suffering ongoing symptoms after Covid gives the opportunity to get to the bottom of what is causing these after-viral effects, and could lead to help for other long-term conditions.
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