Ever wondered why some people who recovered from Covid-19 still experience constant fatigue, brain fog, muscle pain and heart palpitations?
Researchers from Stellenbosch University suggest that the lingering effects may be linked to changes in the blood, specifically, the formation of tiny clots and overactive immune responses.
A recent study titled Circulating Microclots Are Structurally Associated with Neutrophil Extracellular Traps and Their Amounts Are Elevated in Long Covid Patients found a strong link between microclots (tiny blood clots) and neutrophil extracellular traps (NETs), web-like structures released by white blood cells to fight infections.
The findings suggest that when the normal interaction between microclots and NETs becomes disrupted, it may cause ongoing inflammation and damage to the body, potentially explaining the persistent symptoms of Long Covid.
In 2021, Professor Resia Pretorius from Stellenbosch University’s department of physiological sciences was among the first scientists to detect abnormal microclots in the blood of Covid-19 patients.
According to the new research, Long Covid, which affects an estimated 1.2-million South Africans, has emerged as a widespread and complex condition that impacts several organ systems.
“Current estimates show that between 10% and 30% of people infected with SARS-CoV-2 experience some form of Long Covid,” the study noted, highlighting the urgent need for better diagnostic tools and treatments.
The researchers also found that patients remain at increased risk of blood clot-related complications, such as pulmonary embolism and deep vein thrombosis, for months after infection, especially those who had severe illness.
Overproduction of NETs can fuel inflammation and clot formation, worsening diseases such as infections, autoimmune disorders, and even Long Covid.
— Study co-author Dr Alain Thierry
“This suggests that abnormal blood clotting may contribute to the ongoing symptoms experienced by Long Covid patients through mechanisms like capillary blockage and tissue damage,” the study explained.
How the immune system may play a role
Dr Alain Thierry, from the Montpellier Cancer Institute in France, was among the first scientists to identify the role of NETs in Covid-19. NETs are formed when immune cells, specifically neutrophils, release their DNA to trap and kill pathogens, a process known as NETosis.
However, when this process becomes excessive, it can harm rather than help.
“Overproduction of NETs can fuel inflammation and clot formation, worsening diseases such as infections, autoimmune disorders and even Long Covid,” said Thierry, who co-authored the study.
Key findings
Using advanced imaging and artificial intelligence tools, researchers analysed blood samples from patients with Long Covid and healthy individuals.
They found that:
- patients with Long Covid had higher levels of both microclots and NETs;
- these microclots were larger and more numerous than those found in healthy individuals;
- there was a clear structural connection between microclots and NETs, much stronger in Long Covid patients.
Machine learning tools helped researchers accurately distinguish patients with Long Covid and participants based on these biomarkers, paving the way for new diagnostic methods and personalised treatments.
According to Pretorius, the findings suggest that excessive NETs may make microclots more resistant to breaking down, keeping them in circulation longer and leading to chronic blood vessel damage.
“This interaction could explain why some patients continue to experience symptoms months or even years after infection,” she said.
The study’s authors say understanding how NETs and microclots interact could help develop new therapies to target inflammation and prevent long-term complications in people with Long Covid.
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