If you’re among those still experiencing symptoms months or even years after your initial COVID-19 infection, you’re not imagining things. Your body is still fighting a battle, and recent scientific discoveries are finally helping us understand why some people develop long COVID while others bounce back completely.
The frustrating reality is that understanding the pathophysiology of long COVID is one of the most intriguing and complex challenges facing clinicians in the past 5 years. Beyond what we know about the nervous system and EBV connections, new insights are emerging that validate what you’ve been experiencing and point toward why your symptoms persist.
Your Immune System’s Overzealous Guards
When we have a COVID-19 exposure, certain immune cells called neutrophils rush to the scene like first responders. These cells are potent – they’re designed to trap and destroy invaders using something called neutrophil extracellular traps, or NETs for short.
Imagine these NETs as sticky spider webs that neutrophils throw out to catch and kill viruses and bacteria. Under normal circumstances, this is exactly what you want to happen. The problem occurs when this process doesn’t know when to stop.
When Protection Becomes the Problem
Here’s where things get complicated, and where recent findings help explain your ongoing symptoms. SARS-CoV-2 may directly bind and penetrate neutrophils, causing them to become hyperactivated. Instead of calming down after the initial infection clears, these immune cells get stuck in an endless cycle of activation.
Picture this: your neutrophils keep throwing out those sticky traps, but now they’re not just catching viruses – they’re causing three interconnected problems that feed into each other like a feedback loop:
The Inflammation Loop: The overactive neutrophils keep releasing inflammatory signals, maintaining a state of chronic inflammation throughout your body. This explains why you might feel like you have a low-grade flu that never quite goes away.
The Blood Clotting Loop: This continuous self-stimulation of neutrophils leads, in turn, to systemic inflammation, micro-thromboses, creating tiny blood clots that can affect circulation and oxygen delivery to your tissues. This might explain the fatigue, brain fog, and exercise intolerance that many long COVID patients experience.
The Autoimmune Loop: Perhaps most concerning, the production of autoantibodies, whose significant consequences include the persistence of endothelial and multi-organ damage, and vascular complications. Essentially, your immune system starts attacking your own healthy tissues.
Why Some People and Not Others?
You might wonder why this happens to some people but not others who had similar infections. The answer likely lies in how severely your neutrophils were initially activated and how effectively your body’s natural “off switches” work to calm the immune response. I think this may connect to research showing higher rates of long COVID-19 in people with trauma histories and chronic stress that disrupts nervous system regulation. Poor vagal tone is associated with increased inflammation and the release of inflammatory mediators like histamine, which suggests that nervous system dysregulation could interfere with the body’s ability to properly regulate neutrophil activity and turn off inflammatory responses.
Evidence of ongoing neutrophil activity, B cell memory alterations, and building autoreactivity more than a year post-COVID-19 has been found in many long COVID patients, suggesting that some people’s immune systems simply have trouble returning to their baseline state.
What This Means for Your Symptoms
This new understanding helps explain the wide range of long COVID symptoms that seem so disconnected:
- Fatigue and brain fog: Chronic inflammation affects your brain’s energy systems and neurotransmitter function
- Shortness of breath: A neutrophil-associated inflammatory phenotype was apparent in those who had persistent pulmonary symptoms
- Heart palpitations: Micro-clots and inflammation can affect cardiovascular function
- Joint pain and muscle aches: Ongoing inflammatory processes target these tissues
- Digestive issues: Your gut’s immune system remains hyperactivated
Validation and Hope
First and foremost, if you’re experiencing long COVID symptoms, know that your experience is real and scientifically validated. Inflammatory PASC (Post-Acute Sequelae of COVID-19 ), identifiable through a refined set of 12 blood markers, means that researchers can now actually measure and identify the ongoing immune dysfunction. Some of these 12 labs are pretty conventional, such as CRP or D-Dimer, but others are less common and maybe more difficult for your provider to find in their lab formulary.
- Cytokines:
- Interleukin-6 (IL-6): A key pro-inflammatory cytokine linked to disease severity and prolonged immune activation in acute COVID-19 and PASC. It’s also a potential target for anti-inflammatory therapies.
- Tumor Necrosis Factor-alpha (TNF-α): Another pro-inflammatory cytokine associated with chronic inflammation and tissue damage in PASC.
- Interleukin-10 (IL-10): While typically anti-inflammatory, paradoxically, elevated levels have been linked with worse outcomes in COVID-19, suggesting a complex role in fibrosis and organ healing.
- Interleukin-1β (IL-1β): A pro-inflammatory cytokine associated with the inflammatory response and cytokine storms. It has also been targeted with IL-1 inhibitors in severe COVID-19 cases.
- Interferon-gamma (IFN-γ): A marker of immune activation, elevated levels have been observed in severe COVID-19.
- Chemokines (e.g., CCL2/MCP-1 and CXCL10/IP-10): Play a role in immune cell migration and activation, contributing to inflammation persistence in PASC.
- Acute Phase Proteins:
- C-reactive protein (CRP) / high-sensitivity CRP (hs-CRP): A well-established marker of inflammation, often elevated in patients with PASC and correlating with disease severity and risk of complications.
- Erythrocyte Sedimentation Rate (ESR): Indicates the level of inflammation and may be elevated in PASC patients.
- Ferritin: A marker of immune system activation that can be elevated in hyperinflammatory states and severe outcomes, including PASC.
- Other Markers:
- D-dimer: Indicates blood clot formation and is a strong predictor of thrombotic complications in COVID-19. It may also be a useful biomarker in PASC to guide anticoagulation therapy decisions.
- Soluble urokinase plasminogen activator receptor (suPAR): An indicator of immune activation and disease severity, linked to chronic inflammation and long COVID-related fatigue.
- Neutrophil extracellular traps (NETs): These structures released by neutrophils contribute to inflammation and thrombosis and are elevated in severe COVID-19, potentially making them targets in PASC thromboinflammation.
This isn’t “all in your head” or something you should just “push through.” Your immune system is genuinely stuck in a hyperactive state, and this requires patience with yourself and appropriate medical support.
Moving Forward: What You Can Do
While we don’t yet have definitive treatments that can reset these feedback loops, understanding the mechanisms opens up several potential approaches:
Work with providers like us who understand the nervous system connection and can help support you through strategies to improve vagal tone.
Be patient with your recovery. This continuous self-stimulation of neutrophils leads to a self-perpetuating cycle that takes time to break. Your body needs time to restore its immune balance.
Focus on reducing additional inflammatory stress through gentle movement, stress management, adequate sleep, and anti-inflammatory nutrition when possible.
Monitor your symptoms and pace your activities. Pushing through fatigue might actually trigger more neutrophil activation and worsen the cycle.
The Bigger Picture
What’s particularly validating about this research is that it shows long COVID isn’t just one condition, but rather represents chronic inflammation, neutrophil activity, and autoreactivity that can manifest differently in different people. This explains why long COVID symptoms can be so varied and why treatments that work for one person might not work for another.
The fact that evidence of neutrophil extracellular traps, or NETs, was found in the blood of these individuals means that researchers can now develop targeted therapies to break these harmful feedback loops.
Looking Ahead
This growing understanding represents hope. When we understand the underlying mechanisms causing a problem, we can develop targeted solutions. While researchers are still in the early stages of translating this knowledge into treatments, the research is moving rapidly.
For now, the most important thing is validation: your symptoms are real, they have a biological basis, and they deserve serious medical attention and research. You’re not alone in this experience.
Your patience with your body during this prolonged recovery isn’t just admirable – it’s medically appropriate given what we now understand about the ongoing immune battle happening inside you.
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Thierry, A. R., & Salmon, D. (2024). Inflammation-, immunothrombosis,- and autoimmune-feedback loops may lead to persistent neutrophil self-stimulation in long COVID. Journal of medical virology, 96(8), e29887. https://doi.org/10.1002/jmv.29887
