“By placing “zombie” blood-vessel cells at the centre of these post-viral diseases, our hypothesis weaves together microclots, oxygen debt (the extra oxygen your body needs after strenuous exercise to restore balance), brain-fog, dizziness, gut leakiness (a digestive condition where the intestinal lining allows toxins into the bloodstream) and immune dysfunction into a single, testable narrative.“
Burtram C. Fielding et al., The Conversation
On July 27th, 2025, the online magazine, The Conversation, posted an article from a research group at Stellenbosch University, explaining their research into “zombie” blood-vessel cells and how they believe these may explain the mechanism behind ME/CFS and Long Covid.
Dr Charles Shepherd, MEA Hon. Medical Adviser, provides comment on their research, alongside links to further information about Microclots and ME/CFS.
Extracts
Our research group studies blood and the cardiovascular system in inflammatory diseases, as well as post-viral conditions. We focus on coagulation, inflammation and endothelial cells. Endothelial cells make up the inner layer of blood vessels and serve many important functions, like regulating blood clotting, blood vessel dilation and constriction, and inflammation.
In our review, our international team proposes that certain viruses drive endothelial cells into a half-alive, “zombie-like” state called cellular senescence. Senescent endothelial cells stop dividing, but continue to release molecules that awaken and confuse the immune system. This prompts the blood to form clots and, at the same time, prevent clot breakdown, which could lead to the constriction of blood vessels and limited blood flow.
MEA Comment
This opinion piece largely relates to a controversial and as yet unproven theory that Long Covid, and possibly ME/CFS, is largely caused by vascular/blood vessel disease – in particular problems with the endothelium, the inner lining of blood vessels, and small blood clots called microclots.
Whilst there is some evidence for the presence of microclots in Long Covid there is very little evidence of microclots occurring in ME/CFS.
So, like many of my medical colleagues, I think that the endothelial abnormalities may well play a role on both conditions. However, I am not yet convinced by the microclot hypothesis
Dr Charles Shepherd,
Trustee and Hon. Medical Adviser to the ME Association,
Member of the 2018-2021 NICE guideline on ME/CFS committee,
Member of the 2002 Chief Medical Officer's Working Group on ME/CFS
More Information
- Independent: Millions of people are suffering from brain fog. A new study will find out why | July 27, 2025
- Medical Matters: Microclots | Winter 2024
- Medical Matters: Treatment – Apheresis | Summer 2022
- Long Covid – Cochrane review of microclots and apheresis | July 27, 2023
- Nature: Plasma exchange therapy for the post COVID-19 condition | February 25, 2025