What Causes Long COVID? New Scientific Evidence Brings Important Answers
🧠 What Causes Long COVID? New Scientific Evidence Brings Important Answers
Long COVID affects millions of people worldwide and remains one of the most misunderstood consequences of COVID-19 infection. Many patients experience persistent symptoms such as fatigue, brain fog, breathlessness, pain, sleep disturbance, and exercise intolerance — often long after the original infection has resolved.
A major study published in Nature Immunology, and recently discussed in the Washington Post, has now provided some of the clearest biological explanations to date for why Long COVID occurs and why recovery can be so slow.
Long COVID (also called post-COVID condition) refers to symptoms that persist for four weeks or more after infection with SARS-CoV-2. Symptoms can last months or even years and may occur even after a mild initial illness.
🔬 What did the researchers study?
The research team analysed blood samples from two independent patient groups — one recruited during the early pandemic (2020–21) and another between 2023–24. Participants included:
- People with Long COVID
- People who had COVID but fully recovered
- Uninfected control participants
Using advanced immune profiling, gene expression analysis, and protein measurements, the researchers examined how the immune system behaved long after the initial infection.
❌ Long COVID is not caused by ongoing viral infection
One of the most important findings was what the researchers did not find.
There was no evidence of persistent coronavirus in people with Long COVID:
- No ongoing viral replication
- No higher viral loads
- No abnormal antibody patterns
Long COVID is usually not driven by lingering virus. This helps explain why antiviral treatments have shown little benefit for established Long COVID.
🔥 Chronic inflammation stays switched on
Instead of ongoing infection, the defining feature of Long COVID in this study was persistent immune activation.
People with Long COVID showed ongoing activation of multiple inflammatory pathways for more than six months, including:
- IL-6 inflammatory signalling
- JAK-STAT immune pathways
- NF-κB signalling
- Complement and coagulation pathways
These pathways are normally switched off once an infection resolves — but in Long COVID, they remain abnormally active.
🪫 Immune exhaustion explains ongoing symptoms
The immune system in Long COVID is not only overactive — it also shows signs of exhaustion.
Researchers found:
- Reduced effectiveness of T-cells
- Features of immune “burnout”
- Poor regulation between inflammatory and recovery pathways
This combination of inflammation and immune exhaustion may explain why patients feel persistently unwell, drained, and unable to recover normally — even when routine tests appear normal.
⚙️ Energy and stress-response systems are disrupted
The study also identified abnormalities in pathways involved in:
- Energy production and metabolism
- Amino acid processing
- Hormonal stress responses
- Cellular repair mechanisms
These changes correlated closely with symptom severity and may help explain fatigue, post-exertional symptom flares, pain amplification, and sleep disturbance.
🧪 Symptoms match biological findings
Importantly, the degree of immune activation closely matched the severity of patient-reported symptoms, including:
- Fatigue
- Breathlessness
- Brain fog
- Pain
This provides objective biological evidence that Long COVID symptoms are real, measurable, and not “all in the mind”.
⏱ Long COVID appears to begin early
Another key insight highlighted in both the scientific paper and the Washington Post article is timing.
People who later developed Long COVID already showed stronger inflammatory responses during their initial COVID infection, suggesting that Long COVID may begin early rather than emerging months later.
💡 Why this research matters
As Professor Dan Barouch, the study’s lead author, explained, identifying chronic inflammation as a key feature of Long COVID opens the door to new therapeutic strategies.
Experts interviewed by the Washington Post also emphasised that Long COVID is likely to involve multiple biological pathways, meaning no single treatment will suit everyone.
• Long COVID is a real, biological condition
• It is driven by persistent inflammation and immune dysregulation
• Symptoms have measurable biological correlates
• Scientific understanding — and treatment development — is accelerating
At Pain Spa, we regularly assess and treat patients with persistent symptoms following COVID-19 infection. We recognise that, in a subset of patients, Long COVID symptoms appear to be driven by autonomic nervous system dysregulation and prolonged sympathetic (“fight-or-flight”) activation.
For carefully selected patients, treatments such as ultrasound-guided stellate ganglion block (SGB) may help reduce excessive sympathetic activity and improve symptoms including brain fog, sleep disturbance, fatigue, and autonomic symptoms such as palpitations or heightened stress responses.
While SGB is not a cure for Long COVID and does not benefit everyone, emerging observational evidence suggests it may be helpful for patients with prominent autonomic features. At Pain Spa, SGB is offered after careful clinical assessment and as part of a broader, individualised management plan, with a strong emphasis on safety, realistic expectations, and evidence-informed care.