Could tiny blood clots cause long COVID’s puzzling symptoms?

Scientists debate evidence for a micro-clot hypothesis that has some people pursuing potentially risky treatments

Authors: Cassandra Willyard Nature 608, 662-664 (2022)doi: https://doi.org/10.1038/d41586-022-02286-7

When Lara Hawthorne, an illustrator in Bristol, UK, began developing strange symptoms after having COVID-19, she hoped that they weren’t due to the virus. Her initial illness had been mild. “I’ve been triple vaccinated. I felt quite protected,” she says. But months later, she was still sick with a variety of often debilitating symptoms: earaches, tinnitus, congestion, headaches, vertigo, heart palpitations, muscle pain and more. On some days, Hawthorne felt so weak that she could not get out of bed. When she finally saw her physician, the diagnosis was what she had been dreading: long COVID.

Unable to find relief, she became increasingly desperate. After reading an opinion piece in The Guardian newspaper about how blood clots might be to blame for long COVID symptoms, Hawthorne contacted a physician in Germany who is treating people with blood thinners and a procedure to filter the blood. She hasn’t heard back yet — rumour has it that people stay on the waiting list for months — but if she has the opportunity to head there for these unproven treatments, she probably will. “I don’t want to wait on my health when I’m feeling so dreadful,” she says.

Researchers are baffled by long COVID: hundreds of studies have tried to unpick its mechanism, without much success. Now some scientists, and an increasing number of people with the condition, have been lining up behind the as-yet-unproven hypothesis that tiny, persistent clots might be constricting blood flow to vital organs, resulting in the bizarre constellation of symptoms that people experience.

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Proponents of the idea (#teamclots, as they sometimes refer to themselves on Twitter) include Etheresia Pretorius, a physiologist at Stellenbosch University in South Africa, and Douglas Kell, a systems biologist at the University of Liverpool, UK, who led the first team to visualize micro-clots in the blood of people with long COVID. They say that the evidence implicating micro-clots is undeniable, and they want trials of the kinds of anticoagulant treatment that Hawthorne is considering. Pretorius penned the Guardian article that caught Hawthorne’s attention.

But many haematologists and COVID-19 researchers worry that enthusiasm for the clot hypothesis has outpaced the data. They want to see larger studies and stronger causal evidence. And they are concerned about people seeking out unproven, potentially risky treatments.

When it comes to long COVID, “we’ve now got little scattered of bits of evidence”, says Danny Altmann, an immunologist at Imperial College London. “We’re all scuttling to try and put it together in some kind of consensus. We’re so far away from that. It’s very unsatisfying.”

Cascade of clots

Pretorius and Kell met about a decade ago. Pretorius had been studying the role of iron in clotting and neglected to cite some of Kell’s research. When he reached out, they began chatting. “We had a Skype meeting and then we decided to work together,” Pretorius says. They observed odd, dense clots that resist breaking down for years in people with a variety of diseases. The research led them to develop the theory that some molecules — including iron, proteins or bits of bacterial cell wall — might trigger these abnormal clots.

Blood clotting is a complex process, but one of the key players is a cigar-shaped, soluble protein called fibrinogen, which flows freely in the bloodstream. When an injury occurs, cells release the enzyme thrombin, which cuts fibrinogen into an insoluble protein called fibrin. Strands of fibrin loop and criss-cross, creating a web that helps to form a clot and stop the bleeding.

Under a microscope, this web typically resembles “a nice plate of spaghetti”, Kell says. But the clots that the team has identified in many inflammatory conditions look different. They’re “horrible, gunky, dark”, Kell says, “such as you might get if you half-boiled the spaghetti and let it all stick together.” Research by Kell, Pretorius and their colleagues suggests that the fibrin has misfolded1, creating a gluey, ‘amyloid’ version of itself. It doesn’t take much misfolding to seed disaster, says Kell. “If the first one changes its conformation, all the others have to follow suit”, much like prions, the infectious misfolded proteins that cause conditions such as Creutzfeldt–Jakob disease.

Long-COVID treatments: why the world is still waiting

Pretorius first saw these strange, densely matted clots in the blood of people with a clotting disorder2, but she and Kell have since observed the phenomenon in a range of conditions1 — diabetes, Alzheimer’s disease and Parkinson’s disease, to name a few. But the idea never gained much traction, until now.

When the pandemic hit in 2020, Kell and Pretorius applied their methods almost immediately to people who had been infected with SARS-CoV-2. “We thought to look at clotting in COVID, because that is what we do,” Pretorius says. Their assay uses a special dye that fluoresces when it binds to amyloid proteins, including misfolded fibrin. Researchers can then visualize the glow under a microscope. The team compared plasma samples from 13 healthy volunteers, 15 people with COVID-19, 10 people with diabetes and 11 people with long COVID3. For both long COVID and acute COVID-19, Pretorius says, the clotting “was much more than we have previously found in diabetes or any other inflammatory disease”. In another study4, they looked at the blood of 80 people with long COVID and found micro-clots in all of the samples.

So far, Pretorius, Kell and their colleagues are the only group that has published results on micro-clots in people with long COVID.

But in unpublished work, Caroline Dalton, a neuroscientist at Sheffield Hallam University’s Biomolecular Sciences Research Centre, UK, has replicated the results. She and her colleagues used a slightly different method, involving an automated microscopy imaging scanner, to count the number of clots in blood. The team compared 3 groups of about 25 individuals: people who had never knowingly had COVID-19, those who had had COVID-19 and recovered, and people with long COVID. All three groups had micro-clots, but those who had never had COVID-19 tended to have fewer, smaller clots, and people with long COVID had a greater number of larger clots. The previously infected group fell in the middle. The team’s hypothesis is that SARS-CoV-2 infection creates a burst of micro-clots that go away over time. In individuals with long COVID, however, they seem to persist.

Dalton has also found that fatigue scores seem to correlate with micro-clot counts, at least in a few people. That, says Dalton, “increases confidence that we are measuring something that is mechanistically linked to the condition”.

In many ways, long COVID resembles another disease that has defied explanation: chronic fatigue syndrome, also known as myalgic encephalomyelitis (ME/CFS). Maureen Hanson, who directs the US National Institutes of Health (NIH) ME/CFS Collaborative Research Center at Cornell University in Ithaca, New York, says that Pretorius and Kell’s research has renewed interest in a 1980s-era hypothesis about abnormal clots contributing to symptoms. Pretorius, Kell and colleagues found amyloid clots in the blood of people with ME/CFS, but the amount was much lower than what they’ve found in people with long COVID5. So clotting is probably only a partial explanation for ME/CFS, Pretorius says.

Micro-clot mysteries

Where these micro-clots come from isn’t entirely clear. But Pretorius and Kell think that the spike protein, which SARS-CoV-2 uses to enter cells, might be the trigger in people with long COVID. When they added the spike protein to plasma from healthy volunteers in the laboratory, that alone was enough to prompt formation of these abnormal clots6.

Bits of evidence hint that the protein might be involved. In a preprint7 posted in June, researchers from Harvard University in Boston, Massachusetts, reported finding the spike protein in the blood of people with long COVID. Another paper8 from a Swedish group showed that certain peptides in the spike can form amyloid strands on their own, at least in a test tube. It’s possible that these misfolded strands provide a kind of template, says Sofie Nyström, a protein chemist at Linköping University in Sweden and an author of the paper.

Micrographs of platelet poor plasma of a healthy volunteer showing few microclots,and post-COVID-19 infection showing microclots
Micro-clots (green) in a study participant before SARS-CoV-2 infection (left four panels) and in the same person after they developed long COVID (right four panels).Credit: E. Pretorius et al./Cardiovasc. Diabetol. (CC BY 4.0)

A California-based group found that fibrin can actually bind to the spike. In a 2021 preprint9, it reported that when the two proteins bind, fibrin ramps up inflammation and forms clots that are harder to degrade. But how all these puzzle pieces fit together isn’t yet clear.

If the spike protein is the trigger for abnormal clots, that raises the question of whether COVID-19 vaccines, which contain the spike or instructions for making it, can induce them as well. There’s currently no direct evidence implicating spike from vaccines in forming clots, but Pretorius and Kell have received a grant from the South African Medical Research Council to study the issue. (Rare clotting events associated with the Oxford–AstraZeneca vaccine are thought to happen through a different mechanism (Nature 596, 479–481; 2021).)

Raising safety concerns about the vaccines can be uncomfortable, says Per Hammarström, a protein chemist at Linköping University and Nyström’s co-author. “We don’t want to be over-alarmist, but at the same time, if this is a medical issue, at least in certain people, we have to address that.” Gregory Poland, director of the Mayo Clinic’s vaccine research group in Rochester, Minnesota, agrees that it’s an important discussion. “My guess is that spike and the virus will turn out to have a pretty impressive list of pathophysiologies,” he says. “How much of that may or may not be true for the vaccine, I don’t know.”

Dearth of data

Many researchers find it plausible and intriguing that micro-clots could be contributing to long COVID. And the hypothesis does seem to fit with other data that have emerged on clotting. Researchers already know that people with COVID-19, especially severe disease, are more likely to develop clots. The virus can infect cells lining the body’s 100,000 kilometres of blood vessels, causing inflammation and damage that triggers clotting.

Those clots can have physiological effects. Danny Jonigk, a pathologist at Hanover Medical School in Germany, and his colleagues looked at tissue samples from people who died of COVID-19. They found micro-clots and saw that the capillaries had split, forming new branches to try to keep oxygen-rich blood flowing10. The downside was that the branching introduces turbulence into the flow that can give rise to fresh clots.

How common is long COVID? Why studies give different answers

Several other labs have found signs that, in some people, this tendency towards clotting persists months after the initial infection. James O’Donnell, a haematologist and clotting specialist at Trinity College Dublin, and his colleagues found11 that about 25% of people who are recovering from COVID-19 have signs of increased clotting that are “quite marked and unusual”, he says.

What is less clear is whether this abnormal clotting response is actually to blame for any of the symptoms of long COVID, “or is it just, you know, another unusual phenomenon associated with COVID?” O’Donnell says.

Alex Spyropoulos, a haematologist at the Feinstein Institutes for Medical Research in New York City, says the micro-clot hypothesis presents “a very elegant mechanism”. But he argues that much more work is needed to tie the lab markers to clinical symptoms. “What’s a little bit disturbing is that these authors and others make huge leaps of faith,” Spyropoulos says.

Jeffrey Weitz, a haematologist and clotting specialist at McMaster University in Hamilton, Canada, points out that the method Pretorius’s team is using to identify micro-clots “isn’t a standard technique at all”. He adds: “I’d like to see confirmation from other investigators.” Micro-clots are difficult to detect. Pathologists can spot them in tissue samples, but haematologists tend to look for markers of abnormal clotting rather than the clots themselves.

Other, larger studies of long COVID have failed to find signs of clotting. Michael Sneller, an infectious-disease specialist, and his colleagues at the NIH in Bethesda, Maryland, thoroughly examined 189 people who had been infected with SARS-CoV-2, some with lingering symptoms and some without, and 120 controls12. They did not specifically look for micro-clots. But if micro-clots had been clogging the capillaries, Sneller says, they should have seen some evidence — tissue damage in capillary-rich organs such as the lungs and kidneys, for example. Micro-clots might also damage red blood cells, leading to anaemia. But Sneller and his colleagues found no signs of this in any of the lab tests.

The four most urgent questions about long COVID

Kell and Pretorius argue that just because this study didn’t find any evidence of micro-clots doesn’t mean they aren’t there. One of the key issues with long COVID is that “every single test comes back within the normal ranges”, Pretorius says. “You have desperately ill patients with no diagnostic method.” She hopes that other researchers will read their papers and attempt to replicate their results. “Then we can have a discussion,” she says. The ultimate causal proof, she adds, would be people with long COVID feeling better after receiving anticoagulant therapies.

There is some limited evidence of this. In an early version of a preprint, posted in December 2021, Kell, Pretorius and other researchers, including physician Gert Jacobus Laubscher at Stellenbosch University, reported that 24 people who had long COVID and were treated with a combination of two antiplatelet therapies and an anticoagulant experienced some relief13. Participants reported that their main symptoms resolved and that they became less fatigued. They also had fewer micro-clots. Pretorius and Kell are working to gather more data before they try to formally publish these results. But other physicians are already using these medications to treat people with long COVID. Some are even offering a dialysis-like procedure that filters fibrinogen and other inflammatory molecules from the blood. To O’Donnell, such treatment feels premature. He accepts that some people with long COVID are prone to clots, but leaping from a single small study to treating a vast number of people is “just not going to wash in 2022 in my book”, he says. Sneller agrees. “Anticoagulating somebody is not a benign thing. You basically are interfering with the blood’s ability to clot,” he says, which could make even minor injuries life-threatening.

Kell says he’s tired of waiting for a consensus on how to treat long COVID. “These people are in terrible pain. They are desperately unwell,” he says. Altmann understands that frustration. He gets e-mails almost daily, asking: “Where are the drug trials? Why does it take so long?” But even in the midst of a pandemic, he argues, researchers have to follow the process. “I’m not rubbishing anybody’s data. I’m just saying we’re not there yet,” he says. “Let’s join up the dots and do this properly.”

References

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Warning to anyone who’s had Covid as scientists discover symptoms that can last for TWO YEARS

Authors: Vanessa Chalmers, Digital Health Reporter May 11 2022  May 12 2022

DOCTORS have discovered the symptoms of Covid that can last for two years or more. 

Their research has shown that half of patients admitted to hospital are still likely to have at least one persistent problem two years later.

The study, published in The Lancet Respiratory Medicine, has the longest follow-up period of patients to date. 

Researchers are only able to analyse what symptoms exist after two years given the coronavirus emerged in late 2019.

So it’s possible problems like fatigue and anxiety could stick around even longer.

Lead author Professor Bin Cao, of the China-Japan Friendship Hospital, China, said: “Our findings indicate that for a certain proportion of hospitalised Covid-19 survivors, while they may have cleared the initial infection, more than two years is needed to recover fully from Covid-19.”

The study involved almost 1,200 patients, aged 57 on average, who were infected with the bug in the early phase of the pandemic.

They had all been treated in Wuhan, China, then assessed six months, 12 months and two years after discharge.

Researchers looked at their walking abilities, mental health, quality of life and more.

Covid patients were generally found to be in poorer health than those in the general population two years after infection.

They reported:

  • Fatigue or muscle weakness (31 per cent of Covid patients compared to five per cent in the general population)
  • Sleep difficulties (51 per cent compared with 14 per cent)
  • Pain or discomfort (23 per cent compared with five per cent)
  • Anxiety or depression (12 per cent compared with five per cent)

Joint pain, palpitations, dizziness, and headaches were also more common among previously hospitalised Covid patients.

Not all of those hospitalised were affected, however.

More than half (55 per cent) of participants had at least one symptom of Covid at two years, and were therefore considered “long Covid” patients.

The researchers then compared the long Covid group with the group of participants who had endured Covid, but gotten better. 

Those with long Covid had more pain (35 per cent vs 10 per cent), and mobility issues (five per cent vs one per cent) than their fully recovered counterparts.

Some 13 per cent showed symptoms of anxiety and 11 per cent depression, compared with three per cent and one per cent in non-long Covid patients, respectively. 

The researchers said it’s not possible to say whether problems like these are specific to Covid, or whether other hospital patients experience them.

Long Covid is defined as someone who still battles symptoms beyond four weeks in the UK.

It may be defined as ongoing Covid (four to 12 weeks), or post-Covid syndrome (more than 12 weeks) by medics.

The symptoms may include fatigue, a cough, breathlessness, muscle or joint pain, loss of taste of smell and brain fog.

Long COVID’s daunting toll seen in study of pandemic’s earliest patients

Authors: Melissa Healy   6 hrs ago

COVID-19 patients in Wuhan were among the pandemic’s first victims, and a comprehensive new study finds that a year after shaking the coronavirus, survivors were more likely than their uninfected peers to suffer from mobility problems, pain or discomfort, anxiety and depression.

detailed accounting of 1,276 people hospitalized for COVID-19 in the pandemic’s opening months reveals that a full year later, almost half continued to report at least one lingering health problem that is now considered a symptom of “long COVID.”

One out of five said they had continued fatigue and/or muscle weakness, and 17% said they were still experiencing sleep difficulties. Just over one in four said they were suffering anxiety or depression in the wake of their bout with the SARS-CoV-2 virus.

For the growing number of patients who identify themselves as COVID “long haulers,” the new accounting offers cause for optimism — and concern. The period from six to 12 months after infection brought improvement for many. But most patients struggling with symptoms at the six-month mark were not yet well six months later.

The findings, catalogued by a team of Chinese researchers, were published late Thursday in the medical journal Lancet.

“This is not good news,” said David Putrino, a rehabilitation specialist who works with COVID long haulers at Mount Sinai Hospital in New York. “If you run the numbers here, about one-third of the group that had persistent symptoms are getting better after 12 months, while two-thirds are not.”

Putrino also called the findings a “wake-up call” to public health officials that even when the pandemic is over — a distant enough prospect in the midst of a fourth wave of infections — its downstream consequences will not be.

“We’re going to need resources for many years to come to deal with these patients,” he said.

There will be a lot of them. More than 87,000 COVID-19 patients are being hospitalized each day in the United States, and 2.7 million have receiving hospital care in the past year alone.

The half who contend with persistent symptoms will show up in doctors’ offices with clusters of vague and perplexing complaints including brain fog, heart palpitations, pain and exhaustion. And despite emerging evidence that time and specialized treatment can help many to improve, few will have the wherewithal to spend months in intensive rehabilitation for their symptoms, Putrino said.

An editorial published alongside the new study noted that only 0.4% of COVID long haulers are receiving rehabilitative treatment for their symptoms.

Even as scientists puzzle over the common biological mechanisms of long COVID’s diverse symptoms, healthcare providers “must acknowledge and validate the toll of the persistent symptoms of long COVID on patients, and health systems need to be prepared to meet individualised, patient-oriented goals, with an appropriately trained workforce,” Lancet’s editors wrote.

The new research also offered some glimmers of hope.

When the study’s COVID-19 patients were examined at six months, 68% said they had at least one of 15 symptoms considered hallmarks of long COVID, which is also known as Post-Acute Sequelae of COVID, or PASC. At one year, 49% were still afflicted by at least one of those symptoms.

The proportion of patients with ongoing muscle weakness and fatigue dropped from 52% to 20% during that time. Patients experiencing loss of smell dropped from 11% to 4%, and those afflicted with sleep problems fell from 27% to 17%. The 22% who reported hair loss at six months dwindled to 11% a full year out.

At the same time, the numbers of patients reporting breathing difficulties saw a slight increase, rising from 26% at six months to 30% after a year. Likewise, patients who reported new depression or anxiety increased from 23% to 26% during that period.

Study co-author Xiaoying Gu from the China-Japan Friendship Hospital in Beijing said the slight uptick in anxiety and depression was, like all of long COVID’s symptoms, hard to explain.

The psychiatric symptoms “could be caused by a biological process linked to the virus infection itself, or the body’s immune response to it,” he said. “Or they could be linked to reduced social contact, loneliness, incomplete recovery of physical health or loss of employment associated with illness.”

Patients who required mechanical ventilation were more likely than those with less severe illness to have measurable lung impairment and abnormal chest X-rays at both six and 12 months.

But in the tally of more subjective long COVID symptoms, the difference between the most severely ill and those who required no supplemental oxygen at all was very small.

That finding underscores the fact that even patients who are only mildly ill are at risk of developing a range of persistent symptoms.

Of the study population’s 479 patients who held jobs when the pandemic struck, 88% had returned to work a year after their illness. Most of the 57 who did not return said they either could not or were unwilling to do the tasks required of them.

The findings from the Wuhan patients also tracked with the widespread observation that persistent post-COVID infection symptoms are more common in women than in men. Women who had been hospitalized for COVID-19 were twice as likely as their male counterparts to report depression or anxiety 12 months later. In addition, they were close to three times as likely to show evidence of impaired lung function, and 43% more likely to report symptoms of fatigue and muscle weakness.

All of the study’s participants were treated at a single hospital in Wuhan, where reports of a mysterious new form of pneumonia first surfaced in December 2019. The researchers followed a large group of patients sickened in the first five months that the outbreak.

That makes the Lancet report one of the earliest and largest accounts of lingering COVID-19 symptoms to be tallied and vetted by other researchers, and the only one to compare such patients to a group of uninfected peers matched on a wide range of demographic and health attributes.

One thing is already clear, the journal editors noted: “Long COVID is a modern medical challenge of the first order.”

This story originally appeared in Los Angeles Times.

Chronic Fatigue May Be Long-Term Effect of COVID

Authors: Carolyn Crist

A large number of people who contract the coronavirus don’t fully recover in a few weeks, and many of them are experiencing chronic fatigue.

More than a third of those who have tested positive for COVID-19 and have symptoms don’t feel like they’re back to normal, even weeks later, according to a new CDC report.

“COVID-19 can result in prolonged illness, even among young adults without underlying chronic medical conditions,” the CDC COVID-19 Response Team wrote.

About 35% of people surveyed for the study said they weren’t back to their “usual state of health,” according to the report. Among those between ages 18-34 without prior chronic medical conditions, one in five said they hadn’t completely recovered.

Scientists are beginning to study whether the coronavirus may create post-viral issues such as myalgic encephalomyelitis, which is also known as chronic fatigue syndrome. Common symptoms include brain fog, fatigue, pain, immune issues, and malaise after exercise.

Those who are experiencing long-term symptoms after contracting the coronavirus — called the “COVID long-haulers” — are beginning to talk about the months-long issues they’ve had, according to CNN.

Tens of thousands of people have joined online support groups on social media, private chat channels and special interest websites, where they can talk about their symptoms and what to do as they recover.

For More Information: https://www.webmd.com/lung/news/20200809/chronic-fatigue-may-be-long-term-effect-of-covid