Long Covid Newsletter
Issue #21January 26, 20267 studies

Long COVID markers flag persistent immune activation

This week's research reveals how long COVID hijacks the immune system and affects millions of children, while new studies point toward potential treatments and biological markers.

🧬 Immune system stays stuck in overdrive after COVID

  • 159 long COVID patients showed significantly elevated markers of immune system activation compared to 76 people who recovered normally (p = 0.0003)

  • Four specific immune markers—including proteins from three different immune pathways—could predict long COVID with 79.6% accuracy

  • The lectin pathway, which can be targeted with existing drugs, appears to drive persistent inflammation months after initial infection

Why it matters: This identifies specific immune pathways that stay hyperactive in long COVID, potentially explaining why symptoms persist and pointing toward treatments that could dial down this overactive immune response.

🎖️ Top 10% journal 🔗 Immunology Journal Article 🗓️ Jan 25

Key Findings

📊 School kids with long COVID miss excessive school days

  • 1.4% of all US school-aged children (roughly 700,000 kids) have experienced long COVID at some point

  • Among children with prior COVID, those with long COVID were twice as likely to report memory problems (18.3% vs 8.6%)

  • Long COVID significantly increased the odds of missing more than 18 school days per year due to illness

💡 Long COVID may be creating a hidden educational crisis, with hundreds of thousands of children struggling with memory issues and chronic absenteeism.
🎖️ Top 10% journal 🔗 Emerging infectious diseases Journal Article 🗓️ Jan 22

🧠 Long COVID and chronic fatigue syndrome share identical patterns

  • 143 long COVID patients and 170 chronic fatigue syndrome patients showed nearly identical test results across multiple body systems

  • 92% of long COVID patients and 88% of chronic fatigue patients had reduced brain blood flow when standing up

  • Both groups showed similar rates of nerve damage (67% vs 53%) and heart rhythm problems (22% vs 19%)

💡 These conditions may share the same underlying biological mechanisms, suggesting treatments for chronic fatigue syndrome could help long COVID patients.
Top 30% journal 🔗 PloS one Journal Article 🗓️ Jan 23

🔬 Spike protein alone triggers long COVID-like symptoms in mice

  • Mice exposed to just the COVID spike protein (without the full virus) developed inflammation and blood clotting problems 8-16 days later

  • 40% of mice died from these delayed effects, which resembled post-COVID complications in humans

  • Aspirin treatment significantly reduced both deaths and weight loss in affected mice

💡 The spike protein itself may drive long-term complications, and common blood thinners like aspirin might help prevent some post-COVID problems.
Top 20% journal 🔗 Journal of virology Journal Article 🗓️ Jan 21

💡 Stress hormone patterns disrupted for months after COVID

  • 83 long COVID patients and 13 recovered patients both showed abnormal cortisol rhythms compared to healthy people

  • Morning cortisol levels were reduced (p<0.01) and evening levels stayed elevated, flattening the normal daily rhythm

  • Long COVID patients had higher stress-response hormone levels (26 pg/mL vs 13 pg/mL) than those who recovered normally

💡 COVID appears to disrupt the body's internal clock and stress response system, which may explain why fatigue and sleep problems persist.
🎖️ Top 10% journal 🔗 Frontiers in cellular and infection microbiology Journal Article 🗓️ Jan 22

🎯 Children show hidden heart problems up to a year after COVID

  • Children with prior COVID showed persistent reductions in heart muscle function on detailed testing, despite normal standard heart tests

  • 23.6% of children reported long COVID symptoms, with fatigue affecting 16.6% and heart palpitations in 2%

  • Children who had moderate to severe infections showed elevated markers of blood vessel inflammation

💡 Even mild COVID in children may cause subtle but lasting heart changes that only show up on specialized testing.
Top 20% journal 🔗 International journal of cardiology Journal Article 🗓️ Jan 21

🔬 Breathing control systems altered months after recovery

  • 77 people recovered from COVID showed progressively weakening responses to carbon dioxide over 24 months compared to 41 never-infected controls (p = 0.023)

  • Six inflammation markers were unexpectedly decreased for up to one year after recovery

  • Inflammatory markers correlated with changes in how the brain controls breathing during low oxygen conditions

💡 COVID may subtly alter how the brain controls breathing, potentially explaining persistent shortness of breath in some patients.
🎖️ Top 10% journal 🔗 Respiratory research Journal Article 🗓️ Jan 21

Implications

These studies paint a picture of long COVID as a multi-system condition involving overactive immunity, disrupted brain-body communication, and lasting changes to cardiovascular and respiratory control. The similarities with chronic fatigue syndrome suggest shared treatment approaches, while the identification of specific immune pathways and the potential benefits of common medications like aspirin offer hope for targeted interventions.

Studies in this issue

Primary sources used for this newsletter.

  1. Activation of the Lectin Pathway May Cause Ongoing Immune System Imbalance in Long COVID
    main storyImmunology2026-01-25PMID 41581925
  2. Physical difficulties and illness-related school absences in children with and without long COVID in the US, 2022-2023
    key findingEmerging infectious diseases2026-01-22PMID 41570188
  3. Long-Term Heart and Blood Vessel Effects of COVID-19 in Children and the Need for Monitoring
    key findingInternational journal of cardiology2026-01-21PMID 41564976
  4. Long-term COVID-19 effects on body inflammation and breathing control
    key findingRespiratory research2026-01-21PMID 41566332
  5. SARS-CoV-2 spike protein may cause ongoing blood clotting problems after infection
    key findingJournal of virology2026-01-21PMID 41562619
  6. Similar Nervous System Patterns in Long COVID and Chronic Fatigue Syndrome
    key findingPloS one2026-01-23PMID 41576003
  7. Saliva cortisol levels in long COVID linked to wider stress and daily rhythm problems
    key findingFrontiers in cellular and infection microbiology2026-01-22PMID 41568000

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