Lingering COVID-19 symptoms in "long haulers" may be caused by an overload of inflammatory cells "trapped" inside insoluble microscopic blood clots, according to researchers at Stellenbosch University in South Africa.  

Professor Resia Pretorius, a member of the university’s Physiological Sciences Department, made the finding with her research team while studying micro clots in blood samples of individuals with "long COVID." 

"We found high levels of various inflammatory molecules trapped in micro clots present in the blood of individuals with long COVID," Pretorius stated in a news release. "Some of the trapped molecules contain clotting proteins such as fibrinogen, as well as alpha (2)-antiplasmin". 

A study found "long COVID" symptoms may be caused by trapped inflammatory cells in micro blood clots. (iStock, File)


Fibrinogen is a protein involved with clot formation, while the molecule, Alpha (2)-antiplasmin, prevents the breakdown of blood clots, the authors explained in the release.  

Typically, the body is able to maintain a balance between the process of blood clotting (thickening of the blood to prevent blood loss after an injury) and fibrinolysis (the breakdown of fibrin in blood to prevent blood clot formation), according to health experts. 

However, when high levels of alpha (2)-antiplasmin are present in the blood of patients infected with COVID-19 and those dealing with "long COVID," the body’s ability to break down the clots is significantly hampered, the researchers explained in the study. 

The researchers also noted a significant discovery, that the samples of blood plasma collected from acute COVID-19 and "long COVID" patients continued to deposit insoluble pellets at the bottom of the tubes of samples.

The research team was the first to report finding these micro clots in blood samples of COVID patients, helping solve another puzzling component of the disease, according to the study.  

"Of particular interest is the simultaneous presence of persistent anomalous micro clots and a pathological fibrinolytic system," the authors stated in their report.  

The research teams said these findings provide further evidence that COVID-19 and "long COVID" had significant cardiovascular and clotting pathologies. They recommended further research into treatment therapies to support the clotting and fibrinolytic system in patients with "long COVID" symptoms.  


Mount Sinai South Nassau Chief of Infectious Disease Dr. Aaron Glatt, a spokesman for the Infectious Diseases Society of America, was not involved in the study, but told Fox News: "This is an interesting but very preliminary finding that must be investigated further before any clinical actions can be taken based upon this data." 

The hospital epidemiologist added, "We currently do not have a complete understanding of ‘long COVID’ by any means, but hopefully this will be another piece in the puzzle that will allow us to better understand and treat this important and common complication of COVID-19 illness." 

The study was peer-reviewed and published in the journal Cardiovascular Diabetology  in August 2021.