“The November Factor”: Dr. Bell on ME/CFS & the Flu that Isn’t Flu

by Dr. David S Bell, MD, FAAP*
March 30, 2011

This ME/CFS patient case history is excerpted from Dr. Bell’s book Faces of CFS – Case Histories of Chronic Fatigue Syndrome, published in August, 2000. Each case illustrates a different aspect of the illness that he has studied in patients affected by the ‘Lyndonville Outbreak’ over the years. 

Reprinted with the kind permission of ProHealth: 3/30/11

THE NOVEMBER FACTOR

If robbery is taking without permission, CFS could be the greatest thief of all.

Certainly much has been stolen – the energy to go to work, to play with your children; the ability to enjoy reading a book; the luxury of a refreshing sleep. And, like true, great crimes, the victim sometimes does not even realize that a robbery has been committed.

It is as if the thief in a department store steals the surveillance camera along with the jewelry. The thief of CFS steals not only energy, it may rob the victim of the ability to perceive loss. And the mechanism is simple: Energy is quietly replaced with guilt.

Because the victim feels guilty about experiencing fatigue, the robbery goes unreported. Is it any wonder that this is a controversial illness?

The gift of human nature is the perception of who and what we are. We see ourselves either accurately or inaccurately dependent upon personality and the myriad of factors we call life. We see and feel, relating these experiences to our image of who we think we are. Because fatigue is something to be ashamed of in our society, it may go unreported.

The thief makes off with the priceless essence of our life and replaces it with a plaster statue of guilt. CFS becomes a thief of identity as well as activity. It is possible to say “I am an athlete,” or “’I am a devoted parent.”

When CFS has crept out the back door with energy and hope in a burlap sack, these statements are no longer possible.

It makes no difference whether they were accurate to start with. Even if a fantasy, they were a real fantasy for us. With CFS, even fantasies and dreams are stolen. It is like the movie The Dark Crystal, where the small victims are placed in an evil machine that sucks out their ‘vital essence’. CFS is the thief of the ‘vital essence’.

CFS will do to medicine what quantum mechanics has done to physics. The laws, once considered inviolable, are turned on their head.

Just as we were comfortable with the simplistic notions of physics before relativity, doctors are comfortable with the simple notions of medicine now. It really makes little difference that these notions are incorrect, except to those who are not helped by modern medicine.

When CFS becomes accepted and understood, the simplistic mechanisms will be replaced by theories that are able to explain what is now considered subtle. And, of course, with this understanding will come effective treatments – not just those to improve the symptoms of CFS – but those that will revolutionize medicine.

An example of an illness assumed to be straightforward but is, in fact, bewildering, is the ‘flu.’

A person will say, “I was well until a year ago February when I got the flu.” Or “In the months before I got sick I kept getting the flu.” Or “My immunity must be low because I have had the flu three times this winter.” And of course, when the doctor has no idea of what may be causing your symptoms, comes the standard, “I think it is the flu.”

The longer I study medicine the less I understand about the flu.

Jason Ewing was in his mid-thirties, and apart from being a little overweight, appeared like many up-and-coming executives who trooped into the company offices in the morning, brief case swinging at his right side. He had a promising career until two years ago when he developed a typical case of the flu. Actually, as with many persons with CFS, there was one minor difference. This flu had more-than-usual exhaustion associated with it.

It is a detail frequently overlooked, and it has always been difficult to tell whether there really was more exhaustion with this first flu or whether now, two years later, the fatigue is remembered more prominently.

But at the time Jason took time from work and returned, still not feeling well, a week later. He had not even bothered to see his doctor during the illness because ‘it was just the flu.’ Two weeks later he had crept almost to the point of recovery, and paid it little attention. He was at work when the flu came back a second time.

Jason noted with clarity that this second flu episode was identical to the first.

Not just a similar illness, but the same illness. And now we are getting into strange territory. If a person gets a cold, we assume runny nose, cough, sore throat. But, like ice cream, colds come in many varieties – hundreds in fact – and they are all slightly different.

For example, one cold starts off with a scratchy throat, swollen glands, a little nausea and intense sneezing which lasts a day. But this cold is not the same as that of the neighbor down the street, sore throat and headache but no sneezing. We can call them both colds, but the pattern of symptoms is slightly different, and indeed with viral studies we can see that the initiating virus is also different. But what Jason noticed was that whatever the first virus had been, the second one felt exactly the same.

It would be hard to describe the specific combination of 20 symptoms that made up this particular ‘flu’. It would be like trying to describe an unknown ice cream flavor. In the ice cream store drooling Mocha Vanilla from the corner of your mouth, you say, “that’s it.” And it was a second one. It was separate from the first because he had recovered, implying that his body’s immune mechanism had conquered the first invader. He had returned to work and nearly forgotten about the flu three weeks before.

He went to the doctor and described the course and symptoms, and the exact similarity of the second course to the first. His doctor said that he could not get the same ‘flu’ twice, and that it must be a coincidence that the two were similar.

Jason nodded agreement; they had just made a pact to accept a statement, clothed in the language of science, that was obviously wrong.

There are many viruses that cause the illness we call the common cold. In fact the viruses that cause colds are of several different groups. Flu viruses are a little different, but sometimes it is difficult to say by the symptoms if something is a cold or the flu, because they overlap so much.

In general a cold is mild, one or two days of feeling crummy, and the flu is a week. The flu can be dangerous to older people because they develop secondary infections. And there is a vaccine to cover many of the strains of flu that appear during a given winter. There is the ‘Warsaw’ flu, the ‘Beijing’ flu, the ‘Moscow’ flu. It always seemed to me as a medical student that the different strains of flu were named for communist cities as if they were deliberate attempts at biologic warfare.

Each flu strain is distinct. If you had the ‘Hong Kong’ flu once, you would develop antibodies to this particular viral strain and recover. Then, because of blood cells called memory T-cells, you would remember this strain and not get it again, except in the rare instance after decades when the memory T cells become a little senile. That is why, in general, we get chicken pox or measles once in childhood and then do not get these illnesses again when our children have them.

It is difficult to measure or determine the specific strain of virus during an infection. The government will look for new strains in order to include them into the flu vaccine, but because they take several weeks and are costly they are not routinely done during a flu infection. You go to the doctor and he or she says “You have the flu. Please pay at the front desk.” (As an aside, have you ever noticed that the first ten visits for CFS are said to be due to a virus, and the next ten are said to be due to depression?)

So therefore it is not likely that Jason had the same flu twice in a row. And all of this would not have made any difference if everything got better and resolved.

Jason didn’t care much about T-cells and strain variation. Unfortunately, as he was recovering from this second bout he had a third, again with identical symptoms. There was a very particular set of discomforts that made up this flu and a particular malaise, and it came back full force.

He was treated with antibiotics – maybe it was a sinus infection – and again recovered, only to get it again a fourth time.

Over the next six months the process kept repeating with one significant trend. The episodes of this “flu” began coming closer and closer together and the recovery period shortened.

Six months after the initial episode, they were no longer separate bouts, but a constant illness with the symptoms of abdominal pain, flu-like aching, sore throat, joint pain, headache, blurry vision, trouble concentrating, and, of course, exhaustion.

Instead of being 35 and playing piggy-back with his children, Jason had CFS.

Jason’s six-month onset was not the most common for CFS, but then, again, there are many types of onset in this illness.

Jason’s particular onset, however, raises several important questions:

• Is the illness due to a flu-like virus?

• Is CFS due to an unusual virus that plays hide and seek for the first six months?

• Or does CFS have nothing to do with a virus at all?

Can flu-like symptoms be due to something other than an infection with a tiny microbe? The first time this question ever occurred to me was while I was an intern, working 36-hour shifts in the intensive care nursery. After being up all night and struggling to remember where I parked my car, I would notice that my lymph gland felt swollen and that I was coming down with the ‘flu.’ But after a coma-like sleep I would be recovered and ready to hit the next 36-hour shift.

Another of life’s ironies: They have now made it illegal for interns to work those hours because they would prescribe the wrong medications, put IV fluids in the wrong patients, and make other mistakes due to fatigue. But when a person is disabled with CFS and is constantly in that exhausted state, no one believes them, particularly the former interns.

The most common type of onset in CFS is the “acute onset” flu-like illness that does not resolve.

Yet even in this more frequent type, there are parallels with Jason’s flu. In the acute onset, there is a flu-like event, which after five days or so begins to resolve, just as one would expect with the flu. But after the initial resolution, almost to good health, the symptoms come crashing back and do not disappear again.

This implies that the illness is a little uncertain, it wavers a little at the beginning as if trying to make up its mind. “Shall I come down on Mrs. Peterson or not?” If this is so, it had a really hard time deciding about Jason.

A second unusual detail common to the onset of CFS is the severity of the fatigue during the initial episode of the apparent flu. Again, difficult to differentiate in retrospect, but in the initial illness, the fatigue seemed to be more severe than usual.

When I observed the outbreak in Lyndonville, I felt that this was one detail which set this flu apart from all the others. In fact I felt that you could even guess which people were destined to not get better – although I never hinted that at the time.

The belief I held was that there was a unique infection which caused CFS.

What is it about the flu that causes the symptoms that everyone knows only too well? The conventional explanation is that with an infection, viral or otherwise, chemical mediators designed to fight the infection are released into the blood stream. And it is the presence of these immune substances that actually cause the symptoms.

Part of the evidence for this is that when these substances are infused into healthy people they feel rotten, as if they had the flu. The flu virus and many other viral, and bacterial agents stimulate the production of these normal chemicals, which causes the symptoms. When the body’s immune mechanism destroys the infecting virus or bacteria the production of these immune mediators shuts down with a return to good health.

With Jason, the onset had begun as a typical viral infection followed by repeat episodes or relapses until a continuous illness developed. His course of CFS was then typical: There were good days and bad days, but no days without exhaustion, brain fog, and muscle and joint pain.

There were the usual problems with diagnosis, many specialists consulted, tests run. After 15 months the
diagnosis of CFS was made.

The time when the flu-like events coalesced into a continuous illness was around March of 1995. By summertime the symptoms followed a daily ritual that varied little.

• He would have four or five hours of up-and-around activity, headaches every other day, and so on.

• When he had a bad week, his activity would drop down to two to three hours a day and he would feel more ill.

• On a good week, sometimes coinciding with sunshine and a warm breeze off the lake, the activity could go as high as six good hours a day.

Summer eased on into fall, and into November.

Jason had a severe relapse in November, and felt the same as at the onset of his illness. Exactly the same.

His symptoms worsened to the degree that he was confined to bed for two weeks. He saw his physician who, predictably enough, said he had a virus and to take plenty of fluids and aspirin. On the next visit he was given an antibiotic just to be on the safe side. The flavor of this virus was the same flavor that had started his illness nearly two years earlier.

In this detail, Jason is not unique. CFS is an illness of relapses and remissions, and when patients describe relapses, they describe very similar events to those which occurred in their onset. It is not uncommon to hear, “It was like it was beginning all over again.”

It is because of this observation that the theory of a persistent infection, one that does not resolve, has been a steady thread through the tapestry documenting the history of CFS.

Viral and bacterial candidates come and go, but the proof has been hard to come by.

A second characteristic of Jason’s relapse that seems typical of CFS was its occurrence in November. In our office we call it the “November Factor.” For some reason, people with CFS get sick or sicker in late fall, and our telephone rings off the hook. I believe there is some connection between the unusual onset type and the worsening which occurs in November.

One possible explanation is that the patient has caught another bug. Kids are back in school, a perfect breeding ground for bugs of all sizes. They bring these bugs home, particularly this year’s variety and share them with their parents. The relapse is due to a worsening caused by an intercurrent infection, probably viral. This explanation implies that the relapses, and possibly the onset, are random, due to any old virus.

A second possible explanation is that summer is over and winter is setting in. Many persons with CFS feel better in the summer, perhaps because there is less stress, and more time sitting around on the porch in the warm August air. For young persons and schoolteachers, summer is a time of unsustained activity. That is, instead of eight straight hours of work, school or study, it is an hour here, a couple of hours there with rest in between. Therefore starting back to a day with eight straight hours of work or school can precipitate a relapse.

In this theory, the November factor is the resumption of sustained upright activity after a stress-free, relaxing summer. This possibility implies that a critical amount of sustained activity initiates a relapse, a common experience for persons with CFS.

A third possibility has to do with sunlight. Upstate New York, next to Lake Ontario, undergoes a change in November. The days become short with sunset at 4:45 PM by mid December. Worse yet, water vapor from the lake creates a perpetual cloud bank that drifts over Lyndonville and lingers for the next four months. Mid day is gray, bleak and cold, and all sensible adults have left for Florida.

Perhaps the lack of sunlight alters the brain’s melatonin and the addition of seasonal affective disorder is the November factor. Nearly everyone around here is depressed all winter, a fact that the chamber of commerce leaves out of the brochures. Our great joy in winter is a good nor’easter storm which blows the clouds up to Toronto and gives us several wonderful days of sunlight in which we can shovel snow. My lack of enthusiasm for winter here is more than compensated for by the arrival of the geese in the spring and the following months of cherry and apple blossoms that blanket the county.

There are other possibilities. With the coming of cold and bleak weather in November, people go into their homes, shut the windows, add plastic sheeting to help insulate the windows and begin breathing more carbon monoxide. Carbon monoxide, despite being a deadly poison, is very interesting. It can cause a flu-like illness and prolonged neurologic symptoms very similar to CFS.

Oxygen makes many persons with CFS feel better, at least temporarily. Experiments with hyperbaric chamber treatments, where oxygen is pushed into tissues at high concentrations, have shown improvement in patients with CFS. High altitude sickness also shares many of the symptoms of CFS, again due to decreased oxygen availability to brain cells.

Could it be that the flu-like event is not due to an elusive virus at all, but instead to decreased oxygen availability to the cells? [Note: In 2007, Dr. Bell published Cellular Hypoxia in Neuro-Immune Fatigue – a book laying out his hypothesis that ME/CFS and FM may involve a dysregulation of cellular metabolism leading to the inability of the cells’ mitochondria to utilize oxygen normally.]

Medical science is amazing. The technological advances are astounding. We can rescue one pound preemie babies and transplant hearts, livers, and fingers. We can diagnose retroviruses and have made great strides in treating AIDS. Few pediatricians can boast of seeing measles epidemics, and chicken pox will not be seen by the next generation of doctors. But try to explain something as simple as the flu.

Jason did well for the most part. The one time he got really sick was when I tried to treat him with fludrocortisone.

He got the same flavor flu-like event, initiating the relapse. It was not as severe this time, and it was not in November. He has been the only person treated with this medication who has had a relapse, but it again raises the question of whether the flu-like symptoms are due to infection or an entirely different mechanism. We stopped the medication, left him alone for two weeks and the relapse ended, albeit slowly.

It has now been almost five years since Jason began his journey, and he has improved slowly and steadily. He is up to eight hours of daily activity, and while the symptoms persist, Jason feels grateful that the crushing flu-like malaise has passed.

– Dr. David S Bell, MD, Lyndonville, New York, August 15, 2000

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This article is excerpted with kind permission from Dr. Bell’s classic book Faces of CFS – Case Histories of Chronic Fatigue Syndrome; © David S Bell, MD, 2000.

When do infections lead to long COVID? Scientists close in on triggers and treatments for post-viral syndromes

In 2004, Amy Proal got an infection that changed her life. “I was in my pre-med, last year of college, and totally tanked,” she says. “No one could tell me what it was, everybody said my blood work was fine — sent to a psychiatrist, the usual story.” She started reading papers from her sickbed and soon realized that she wasn’t the only one with unexplained symptoms that lingered after an infection.

A year later, she was diagnosed with ME/CFS (myalgic encephalomyelitis/chronic fatigue syndrome). She managed to improve her symptoms with antivirals and other drugs, and went on to do a PhD in microbiology, studying the lasting consequences of pathogens. In 2018, she co-founded PolyBio, a foundation in Medford, Massachusetts, that advances research on infection-associated chronic illnesses. “Then,” Proal says, “COVID hit.”

Read the rest of this Nature article HERE.

Health-related quality of life changes in patients with Q-fever fatigue syndrome: a four-year follow-up study, 10 years post-infection

Abstract:

Purpose: Q-fever can cause long-term health complications such as Q-fever Fatigue Syndrome (QFS), which may severely impact patients’ Health-Related Quality of Life (HRQoL). This study investigated change of HRQoL in QFS patients over time, and explored predictors associated with change using longitudinal data.

Methods: In this prospective observational study questionnaires were administered among Dutch individuals with self-reported QFS who were registered at Q-support, a foundation that supports, advises and informs Q-fever patients. Participants completed four annual questionnaires between 2021 and 2024, including EQ-5D-5L and EQ VAS to measure HRQoL. Changes in HRQoL were categorized as “improvement”, “deterioration”, or “stable”, using an anchor-based minimal important difference approach. Multinomial logistic regression analyses identified predictors of change.

Results: A total of 199 patients were included in the final analysis. At baseline, median EQ-5D-5L utility index and EQ VAS scores were 0.647 (IQR: 0.352-0.774), and 50.0 (IQR: 34.0-60.0), respectively. After four years, 37% of patients showed improvement in EQ-5D-5L utility, 30% deterioration, and 33% remained stable. Female sex and higher baseline EQ-5D-5L utility were associated with lower odds of improvement or being stable.

Conclusion: More than 10 years post-infection, HRQoL remains consistently low at group level among patients with QFS, with substantial long-term variability in individual outcomes. These findings underscore the chronic nature of QFS, its long-lasting consequences, and the importance of continued monitoring of individual health trajectories. Further studies are warranted to better understand the mechanisms underlying individual differences in recovery and to inform targeted interventions for this patient population.

Source: Stemerdink NC, Heemskerk SCM, Hartman E, Wesseling M, Tieleman P, Burdorf A, Haagsma JA. Health-related quality of life changes in patients with Q-fever fatigue syndrome: a four-year follow-up study, 10 years post-infection. Qual Life Res. 2026 Jun 8;35(7):191. doi: 10.1007/s11136-026-04295-9. PMID: 42260029; PMCID: PMC13246837. https://pmc.ncbi.nlm.nih.gov/articles/PMC13246837/ (Full text)

Reframing ME/CFS: toward a unified mechanistic model of chronic post-infectious diseases

Abstract:

Background: Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a severe multisystem illness marked by post-exertional malaise (PEM), cognitive dysfunction, autonomic disturbance, and impaired physiological resilience. Historically, the absence of validated biomarkers, heterogeneous definitions, and limited investigative capacity have complicated mechanistic interpretation and contributed to the use of psychosocial and rehabilitative frameworks in clinical practice and in parts of the literature.

Main body: Advances in systems biology, accelerated by Long-COVID research, have transformed our understanding of post-infectious syndromes, implicating persistent immune dysregulation, mitochondrial and metabolic reprogramming, endothelial and microvascular dysfunction, abnormal coagulation, lipid-mediated signalling, extracellular vesicle communication, and viral protein-associated immune activation. This review charts the shift from early post-infectious observations through psychosocial dominance to contemporary biological frameworks, emphasising that pathology is state-dependent and revealed under physiological stress.

Conclusion: ME/CFS is thus reframed here as a disorder of impaired adaptive capacity within post-infectious disease biology.

Source: Watton P, Prusty BK. Reframing ME/CFS: toward a unified mechanistic model of chronic post-infectious diseases. J Transl Med. 2026 May 22. doi: 10.1186/s12967-026-08319-3. Epub ahead of print. PMID: 42174604. https://link.springer.com/article/10.1186/s12967-026-08319-3 (Full text available as PDF file)

Designing studies for post-treatment Lyme disease and other infection-associated chronic illnesses

Abstract:

Infection-associated chronic illnesses (IACIs) encompass a spectrum of poorly understood syndromes often marked by significant neurologic and multisystem symptoms following an infectious event. This review focuses on several diseases representative of the IACI spectrum. These are post-treatment Lyme disease syndrome (PTLDS), long COVID, myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and multiple sclerosis (MS). Their clinical and biological complexity, combined with a lack of clear diagnostic criteria and objective available laboratory biomarkers, makes them difficult to distinguish from conditions with overlapping features.

This presents challenges for research studies, as well as diagnosis and clinical management. This diagnostic ambiguity, coupled with heterogeneous patient presentations, has led to challenges in research, including misclassification of study participants and inconsistent or irreproducible findings. Some PTLDS research exemplifies these issues, which also extend to other IACIs.

To advance the field, we highlight key methodological refinements and approaches for studying IACIs, including rigorous participant selection, standardized sample collection protocols, and the use of appropriate control groups, including those with microbiologic proof of the initial infection when known and technologically feasible. We also address broader influences on research quality, such as stigma, historical neglect, and the urgency to find treatments, which have contributed to the proliferation of poorly controlled studies and questionable practices. Drawing lessons from past challenges, we propose a path forward grounded in fit-for-purpose methodological rigour to improve scientific understanding and support evidence-based therapeutic development for IACIs.

Source: Arnaboldi PM, Becker J, Nath A, Coyle PK, Handel A, Sellati TJ, Gomes-Solecki M, Garcet S, Henderson MK, Mullins P, Cowan E, McCombie WR, Wellins AM, Allegretta M, Bergquist J, Schutzer SE. Designing studies for post-treatment Lyme disease and other infection-associated chronic illnesses. Brain. 2026 May 18:awag016. doi: 10.1093/brain/awag016. Epub ahead of print. PMID: 42148664. https://academic.oup.com/brain/advance-article/doi/10.1093/brain/awag016/8586348 (Full text)

Making Invisible Illnesses Visible: Recognizing and Responding to Infection Associated Chronic Conditions

Abstract:

The emergence of post-COVID conditions (PCC) has renewed attention to infection-associated chronic conditions and illnesses (IACCI), including myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and Lyme disease-associated chronic symptoms. Millions of Americans are affected by these debilitating, misunderstood conditions, which share symptom profiles and pathophysiologic abnormalities. IACCI have received insufficient clinical attention and research investment.

We outline elements of a patient-centered approach to care, emphasizing validation of patients’ experiences, multidisciplinary management, and symptom-focused treatment. Opportunities to strengthen clinical practice include a new CMS code for chronic condition management, extended visits, and creation of welcoming care environments. Advances in PCC and ME/CFS research provide a foundation for exploring shared mechanisms and developing targeted therapies. Improved surveillance, harmonized research, and inclusive trial designs are needed to define disease burden and accelerate therapeutic progress. Coordinated action by clinicians, researchers, and policymakers can help address longstanding gaps and improve outcomes for all individuals with IACCI

Source: Iskander JK, Haridopolos S. Making Invisible Illnesses Visible: Recognizing and Responding to Infection Associated Chronic Conditions. Clin Infect Dis. 2026 Apr 9:ciag240. doi: 10.1093/cid/ciag240. Epub ahead of print. PMID: 41967005. https://pubmed.ncbi.nlm.nih.gov/41967005/

Expert perspectives on Myalgic encephalomyelitis/chronic fatigue syndrome – Insights from the 3rd International Conference of the Charité Fatigue Center

Abstract

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a complex, multisystemic disorder mostly triggered by viral infections, with core symptoms including post-exertional malaise (PEM), fatigue, pain, and cognitive dysfunction. Its prevalence has increased significantly in the context of the coronavirus disease 2019 (COVID-19) pandemic. Despite its severity and impact on patients’ quality of life, ME/CFS remains poorly understood.

On May 12 and 13, 2025, the 3rd International Conference hosted by the Charité Fatigue Center brought together nearly 200 researchers from various disciplines on-site, and around 3,700 participants online to discuss recent advances in ME/CFS research, diagnostics, clinical care, and therapeutic trials. The program featured 33 lectures by international experts on key topics such as post-COVID syndrome (PCS), care structures, and pathophysiological mechanisms including cardiovascular dysregulation, immune dysregulation, autoimmune mechanisms, and metabolic dysfunction.

In addition, results from clinical trials addressing disease mechanisms, including those specifically targeting autoantibodies, were presented. While public awareness and funding opportunities have increased in the wake of the pandemic and the emergence of PCS, ME/CFS remains severely underresearched. Sustained and adequately funded research efforts are urgently required to advance understanding, identify diagnostic markers, and develop targeted therapeutic interventions.

Source: Fehrer A, Windzio L, Schoening S, Steiner S, Aschenbrenner AC, Babel N, Behrends U, Bellmann-Strobl J, Cammà G, Cash A, Doehner W, den Dunnen J, Fluge Ø, Franke C, Hoffmann K, Kedor C, Kim L, Löhden W, Mella O, Mihatsch LL, Peluso MJ, Puta C, Putrino D, Ramoji A, Sato W, Sawitzki B, Schlieper G, Schoenfeld Y, Seifert M, Sigurdsson F, Slaghekke A, Sommerfelt K, Sotzny F, Stein E, Steinacker JM, Stingl M, Systrom DM, Tronstad KJ, Wirth K, Wörmann B, Wüst RCI, Yamamura T, Scheibenbogen C. Expert perspectives on Myalgic encephalomyelitis/chronic fatigue syndrome – Insights from the 3rd International Conference of the Charité Fatigue Center. Autoimmun Rev. 2026 Mar 25:104043. doi: 10.1016/j.autrev.2026.104043. Epub ahead of print. PMID: 41895458. https://www.sciencedirect.com/science/article/pii/S1568997226000571 (Full text)

Does Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) Represent a Poly-Herpesvirus Post-Virus Infectious Disease?

Abstract:

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a debilitating multisystem illness with unknown etiology. An estimated 17-24 million people representing approximately 1% of the population are afflicted worldwide. In over half of cases, ME/CFS onset is associated with acute “flu-like” symptoms, suggesting a role for viruses. However, no single virus has been identified as the only etiological agent.

This may reflect the approach employed or more strongly the central dogma associated with herpesviruses replication, which states that a herpesvirus exists in two states, either lytic or latent. The purpose of this review is to address the role that abortive lytic replication may have in the pathogenesis of ME/CFS and other post-acute viral infections and also to raise awareness that these syndromes might be poly-herpesviruses mediated diseases.

Source: Ariza ME, Mena Palomo I, Williams MV. Does Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) Represent a Poly-Herpesvirus Post-Virus Infectious Disease? Viruses. 2025 Dec 16;17(12):1624. doi: 10.3390/v17121624. PMID: 41472292. https://www.mdpi.com/1999-4915/17/12/1624 (Full text)

The lingering shadow of epidemics: post-acute sequelae across history

Significance:
Long COVID, a chronic multisystemic health condition, impacts hundreds of millions around the world. Long COVID has brought light to other related post-acute infection syndromes (PAIS) that are triggered by a wide array of pathogens. This opinion article highlights historical accounts of PAIS through the centuries and emphasizes the need for integrated approaches to understanding and treating PAIS.
Highlights:

  • New or persistent symptoms following COVID-19, known as ‘long COVID’, occur in an estimated 4–20% of pediatric and 10–20% of adult patients after acute infection with SARS-CoV-2. Long COVID is associated with dysregulation of both innate and adaptive immunity.
  • While long COVID is a relatively new clinical entity, post-acute infection syndromes (PAIS) have been well documented for over a century.
  • A wide variety of pathogens are associated with PAIS, including divergent classes of viruses, bacteria, and parasites. While each PAIS has a unique trigger and pathology, similarities in symptom profiles and immunological findings suggest these conditions may share features or involve overlapping biological mechanisms.
  • Despite being well described in the literature, PAIS remain understudied relative to their high disease burden. Patients often face stigma and psychologization from medical professionals when disease biomarkers are not readily apparent, exemplified by the historic dismissal of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS).
Abstract:
The SARS-CoV-2 pandemic has drawn global attention to post-acute infection syndromes (PAIS), with millions affected by post-acute sequelae of COVID-19 (PASC, or Long COVID). While Long COVID is newly defined, PAIS have been described for over a century following epidemic infections. Multiple pathogens – including influenza, Epstein-Barr virus, and Borrelia burgdorferi, among others – can precipitate persistent, poorly understood symptoms. Chronic illnesses such as myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) have long been linked to infectious triggers. This recurring association highlights critical knowledge gaps and underscores the need for systematic investigation. Unlike prior pandemics, the current era offers advanced technologies and analytic tools to address these gaps. Defining the biology of Long COVID may yield broader insights into host–pathogen interactions and mechanisms of chronic illness.
Source: Miller CM, Moen JK, Iwasaki A. The lingering shadow of epidemics: post-acute sequelae across history. Trends Immunol. 2025 Dec 4:S1471-4906(25)00267-4. doi: 10.1016/j.it.2025.10.010. Epub ahead of print. PMID: 41350176. https://www.cell.com/trends/immunology/fulltext/S1471-4906(25)00267-4 (Full text)

Growing recognition of post-acute infection syndromes

Commentary:
Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) and long COVID affect large numbers of people, and constitute a substantial burden to the U.S. and global economies. The article by Eckey et al., in this issue of PNAS (1), adds to the growing evidence that the two illnesses have much in common. Moreover, the illnesses may represent just two examples of an even larger, recently recognized class of illness: post-acute infection syndromes (PAIS) (2).
ME/CFS
This illness first attracted attention in the 1980s. Typically, people suffering from ME/CFS previously have been healthy, and then develop a flu-like illness. While that illness appears initially not unlike previous transient illnesses, and while the respiratory symptoms and fever usually improve, people are left with a severe, persisting fatigue, cognitive problems, worsened symptoms following physical or mental exertion or upright posture, as well as unrefreshing sleep, an illness that can last for years (3, 4). The symptoms are not relieved by rest, and greatly impair a person’s ability to function at work and at home. Some individuals are homebound, some largely bedbound. People with ME/CFS often say, in so many words, “I am no longer the person I was.”
In the 1980s, some scientists suspected that a novel human pathogen was causing the illness. Such speculation seemed reasonable, since a novel virus recently had been discovered to cause the AIDS. However, no single, novel pathogen has emerged as the cause of ME/CFS.
Moreover, the standard laboratory tests that were performed in the 1980s generally came back “normal,” leading some to believe there were no underlying biological abnormalities to explain the symptoms. However, over the past 40 y, thousands of studies have identified many underlying abnormalities involving the brain, immune system, energy metabolism, redox imbalance, vascular injury, and gut microbiota (4–9). The symptoms of the illness are, indeed, accompanied by objective abnormalities.
Despite the fact that—in the United States, alone—the illness is estimated to affect up to 3.1 million people, and to generate direct and indirect expenses of approximately $36 to 51 billion annually (3, 10), relatively few investigators have sought to study the illness: the initial skepticism about whether the illness had a biological basis may have created a lingering stigma. That skepticism faded, to some degree, following publication in 2015 of a report from the U.S. National Academies of Science, Engineering and Medicine highlighting the importance of the problem (3).
Long COVID
Then, along came the COVID-19 pandemic. It was predicted that the pandemic would greatly increase the number of people with an ME/CFS-like illness (11), and that has proved to be the case. Many who have “recovered” from acute COVID-19, even from mild cases, have developed a persisting illness (called “long COVID”) with symptoms much like ME/CFS. The cumulative global incidence of long COVID may be as high as 400 million individuals (5, 8), and the costs to the U.S. and global economy (not including the direct costs of healthcare) may be several trillion dollars in the next 5 to 10 y (8, 12).
Comparing ME/CFS and Long COVID
The similarity of the symptoms seen in ME/CFS and long COVID is underscored by the report from Eckey et al. (1). The study involved a survey of nearly 4,000 people with these illnesses. Participants recorded the prevalence and severity of a large number of symptoms, comorbid illnesses, and responses to different treatments.
The authors recognize that such a survey has important limitations. The diagnoses of ME/CFS, long COVID, and comorbid illnesses were self-reported, and not determined by protocol-directed objective testing—although such testing often had been performed by their doctors. Likewise, the responses to different treatments were self-reported, not the results of randomized, placebo-controlled trials. Nevertheless, the large number of study subjects, and the consistency of their responses, suggests that their responses are valid.
Symptoms.
As seen in figure 1 of the report by Eckey et al. (1), the frequency of each of the symptoms is very similar in both illnesses. At the same time, there may be subgroups of people with both ME/CFS and long COVID in whom different symptoms are predominant: it is possible that these subgroups have different underlying pathophysiology, responses to treatments, and prognosis.
Underlying Pathophysiology.
Of course, the fact that the symptoms and symptom frequency are similar does not necessarily mean the two illnesses share an underlying pathophysiology. Nevertheless, it appears that they do. A detailed analysis of the underlying biological abnormalities seen in both illnesses reveals a striking similarity (6).
Comorbid Diseases.
The survey conducted by Eckey et al., addressed two other dimensions by which to compare the two illnesses. First, the survey found that people with the two illnesses frequently had the same comorbid conditions, particularly postural orthostatic tachycardia syndrome (POTS), migraine, dysautonomia, anxiety and depression, mast cell activation syndrome (MCAS), Ehlers–Danlos syndrome (EDS)/joint hypermobility, and attention deficit disorder (ADD) (1).

Response to Therapies.

Patients with the two illnesses also responded similarly to specific treatments. Remarkably, even at the level of specific symptoms, responses were similar in people with the two illnesses, and the drugs most effective against particular symptoms would be expected to improve those symptoms, adding credibility to the self-reported improvement (1). Thus, the study is consistent with others in finding similar symptoms in people with the two illnesses and, additionally, finds similar comorbidities and responses to treatment.

PAIS

ME/CFS and long COVID are not the only two illnesses that share very similar symptoms. Over the past century, there have been many reports of an illness with very similar symptoms following multiple different acute bacterial, viral, fungal, and protozoal infections; hence, the proposal to call all of these illnesses PAIS (2). Long COVID surely is a PAIS (since the inciting infectious agent is known), and myalgic encephalomyelitis/ chronic fatigue syndrome (ME/CFS) likely often is (even though the inciting agents often have not been pursued by physicians).

IACIs
PAIS, in turn, are one example of an even larger umbrella category, a group of disorders called IACIs (9, 13). As shown in Fig. 1, we distinguish three categories of IACIs: new organ injury from an infectious agent, such as the development of multiple sclerosis following primary infection with Epstein–Barr virus or duodenal ulcers caused by Helicobacter pylori; accelerated incidence of disease processes that had not yet become apparent before the time of an acute infection (including accelerated atherosclerosis and neurodegeneration post-COVID) (8, 14); and PAIS. Some observers use the term long COVID to include all three categories of illness following acute infection with SARS-CoV-2. We restrict the use of the term long COVID to just the PAIS that can follow SARS-CoV-2 infection.
Read the rest of this article here: https://www.pnas.org/doi/10.1073/pnas.2513877122
Source: A.L. Komaroff, Growing recognition of post-acute infection syndromes, Proc. Natl. Acad. Sci. U.S.A. 122 (29) e2513877122, https://doi.org/10.1073/pnas.2513877122 (2025). https://www.pnas.org/doi/10.1073/pnas.2513877122 (Full text)