Category: History

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)

False Alarm: XMRV, Cancer, and Chronic Fatigue Syndrome

Abstract:

Xenotropic murine leukemia virus (MLV)-related virus (XMRV) was first described in 2006 in some human prostate cancers. But it drew little attention until 2009, when it was also found, as infectious virus and as MLV-related DNA, in samples from people suffering from myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). This discovery was rapidly followed by efforts of the international research community to understand the significance of the association and its potential to spread widely as an important human pathogen.

Within a few years, efforts by researchers worldwide failed to repeat these findings, and mounting evidence for laboratory contamination with mouse-derived virus and viral DNA sequences became accepted as the explanation for the initial findings. As researchers engaged in these studies, we present here a historical review of the rise and fall of XMRV as a human pathogen, and we discuss the lessons learned from these events.

Source: Coffin JM, Kearney MF. False Alarm: XMRV, Cancer, and Chronic Fatigue Syndrome. Annu Rev Virol. 2024 Jul 8. doi: 10.1146/annurev-virology-111821-125122. Epub ahead of print. PMID: 38976866. https://pubmed.ncbi.nlm.nih.gov/38976866/

An Unwanted but Long-Known Company: Post-Viral Symptoms in the Context of Past Pandemics in Switzerland (and Beyond)

Abstract:

Objectives: Some people do not fully recover from an acute viral infection and experience persistent symptoms or incomplete recovery for months or even years. This is not unique to the SARS-CoV-2 virus and history shows that post-viral conditions like post COVID-19 condition, also referred to as Long Covid, are not new. In particular, during and after pandemics caused by respiratory viruses in which large parts of the population were infected or exposed, professional and public attention was increased, not least because of the large number of people affected.

Methods: Given the current relevance of the topic, this article aims to narratively review and summarize the literature on post-viral symptoms during past pandemics and to supplement and illustrate it with Swiss examples from the pandemics of 1890, 1918–1920 and later.

Results: Post-viral diseases were an increasingly emphasised health topic during and after past pandemics triggered by respiratory infections over the last 150 years.

Conclusion: In the next pandemic, it should not be surprising that post-viral conditions will again play a role, and pandemic plans should reflect this.

Source: Staub, Kaspar; Ballouz, Tala; Puhan, Milo (2024). An Unwanted but Long-Known Company: Post-Viral Symptoms in the Context of Past Pandemics in Switzerland (and Beyond). Public Health Reviews, 45:1606966. https://www.ssph-journal.org/articles/10.3389/phrs.2024.1606966/full (Full text)

A Natural History of Disease Framework for Improving the Prevention, Management, and Research on Post-viral Fatigue Syndrome and Other Forms of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome

Abstract:

We propose a framework for the treatment, rehabilitation, and research into Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) using a natural history of disease approach to outline the distinct disease stages, with an emphasis on cases following infection to provide insights into prevention.

Moving away from the method of subtyping patients based on the various phenotypic presentations and instead reframing along the lines of disease progression could help with defining the distinct stages of disease, each of which would benefit from large prospective cohort studies to accurately describe the pathological mechanisms taking place therein. With a better understanding of these mechanisms, management and research can be tailored specifically for each disease stage.

Pre-disease and early disease stages call for management strategies that may decrease the risk of long-term morbidity, by focusing on avoidance of further insults, adequate rest to enable recovery, and pacing of activities.

Later disease stages require a more holistic and tailored management approach, with treatment—as this becomes available—targeting the alleviation of symptoms and multi-systemic dysfunction.

More stringent and standardised use of case definitions in research is critical to improve generalisability of results and to create the strong evidence-based policies for management that are currently lacking in ME/CFS.

Source: O’Boyle S, Nacul L, Nacul FE, Mudie K, Kingdon CC, Cliff JM, Clark TG, Dockrell HM and Lacerda EM. A Natural History of Disease Framework for Improving the Prevention, Management, and Research on Post-viral Fatigue Syndrome and Other Forms of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome. Front. Med. 8:688159. https://www.frontiersin.org/articles/10.3389/fmed.2021.688159/full (Full text)

The 1918 Influenza Pandemic: Back to the Future?

Abstract:

Background: It is just over a century since the 1918 flu pandemic, sometimes referred to as the “mother” of pandemics. This brief retrospective of the 1918 pandemic is taken from the viewpoint of the current SARS-CoV-2/COVID-19 pandemic and is based on a short lecture given during the 2021 Virtual Congress of the ERA-EDTA.

Summary: This review summarizes and highlights some of the earlier pandemic’s salient features, some parallels with today, and some potential learnings, bearing in mind that the flu pandemic occurred over 100 years ago at a time of major turmoil during the climax to WWl, and with limited medical expertise and knowledge, research facilities, or well-structured and resourced healthcare services. While there is little or no information on renal complications at the time, or an effective treatment, some observations in relation to COVID-19 and vaccination are included.

Key Messages: Lessons are difficult to draw from 1918 other than the importance and value of non-pharmaceutical measures to limit viral transmission. While the economic impact of the 1918 pandemic was significant, as it is now with COVID-19, subsequent economic analysis has shown that protecting public health and preserving economic activity are not mutually exclusive. Both H1N1 and SARS-CoV-2 viruses are neurotropic and may cause chronically debilitating neurological diseases, including conditions such as encephalitis lethargica (still debated) and myalgic encephalomyelitis (chronic fatigue syndrome), respectively. Although coronavirus and influenza viral infections have some similarities, they are certainly not the same, as we are realising, and future infectious pandemics may still surprise us, but being “forewarned is forearmed.”

Source: Unwin RJ. The 1918 Influenza Pandemic: Back to the Future? Kidney Blood Press Res. 2021 Oct 18:1-8. doi: 10.1159/000519288. Epub ahead of print. PMID: 34662882. https://pubmed.ncbi.nlm.nih.gov/34662882/ 

ME/CFS: Past, Present and Future

Abstract:

This review raises a number of compelling issues related to the condition of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS). Some historical perspective is necessary in order to highlight the nature of the controversy concerning its causation. Throughout history, a pattern tends to repeat itself when natural phenomena require explanation. Dogma usually arrives first, then it is eventually replaced by scientific understanding. The same pattern is unfolding in relation to ME/CFS, but supporters of the psychological dogma surrounding its causation remain stubbornly resistant, even in the face of compelling scientific evidence to the contrary. Acceptance of the latter is not just an academic issue; the route to proper understanding and treatment of ME/CFS is through further scientific research rather than psychological theorisation. Only then will a long-suffering patient group benefit.

Source: Weir, William, and Nigel Speight. 2021. “ME/CFS: Past, Present and Future” Healthcare 9, no. 8: 984. https://doi.org/10.3390/healthcare9080984 https://www.mdpi.com/2227-9032/9/8/984/htm (Full text)

Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: Organic Disease or Psychosomatic Illness? A Re-Examination of the Royal Free Epidemic of 1955

Abstract:

Background and Objectives: Controversy exists over whether myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is an organic disease or a psychosomatic illness. ME/CFS usually occurs as sporadic cases, but epidemics (outbreaks) have occurred worldwide. Myalgic encephalomyelitis was named to describe an outbreak affecting the lymphatic, muscular, and nervous systems that closed the Royal Free hospital for three months in 1955. Fifteen years later, two psychiatrists concluded that epidemic hysteria was the likely cause. ME/CFS research studies show multiple pathophysiological differences between patients and controls and a possible etiological role for infectious organisms, but the belief that ME/CFS is psychosomatic is widespread and has been specifically supported by the epidemic hysteria hypothesis for the Royal Free outbreak. Our objective was to obtain accounts from ex-Royal Free hospital staff who personally experienced the 1955 outbreak and evaluate evidence for it being an infectious illness versus epidemic hysteria.

Materials and Methods: Statements in the newsletters of two organizations for staff who had worked at the Royal Free hospital invited anyone who had experienced the 1955 Royal Free outbreak to contact the authors. Accounts of the outbreak from telephone interviews and letters were evaluated against the “epidemic hysteria hypothesis” paper and original medical staff reports.

Results: Twenty-seven ex-Royal Free hospital staff, including six who had developed ME, provided descriptions typical of an infectious illness affecting the lymphatic, muscular, and nervous systems, and were not consistent with epidemic hysteria.

Conclusions: The 1955 Royal Free hospital epidemic of myalgic encephalomyelitis was an organic infectious disease, not psychogenic epidemic hysteria.

Source: Underhill R, Baillod R. Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: Organic Disease or Psychosomatic Illness? A Re-Examination of the Royal Free Epidemic of 1955. Medicina (Kaunas). 2020 Dec 26;57(1):E12. doi: 10.3390/medicina57010012. PMID: 33375343. https://www.mdpi.com/1010-660X/57/1/12  (Full text)

Legitimizing myalgic encephalomyelitis/chronic fatigue syndrome: Indications of change over a decade

Abstract:

This commentary identifies recent scientific and clinical milestones that appear to have increased legitimization of myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). These milestones include government-funded reports recognizing the seriousness of ME/CFS, new initiatives for biomedical research sponsored by the US National Institutes of Health, official endorsement of the ME/CFS name, publication of practitioner primers, and the launch of a new peer-review fatigue journal. These positive developments are tempered by ongoing illness challenges including patient stigma, absence of diagnostic markers, a lack of established treatments, and a dearth of researchers and knowledgeable, interested clinicians.

Source: Fred Friedberg (2020) Legitimizing myalgic encephalomyelitis/chronic fatigue syndrome: indications of change over a decade, Fatigue: Biomedicine, Health & Behavior, DOI: 10.1080/21641846.2020.1718292

Neurasthenia: Modern Malady or Historical Relic?

Abstract:

Neurasthenia was a popular diagnosis from 1869 through 1930. Despite being discarded, the core symptoms of neurasthenia can still be found throughout modern society. The present article reviews the symptoms, common course, proposed causes, and common treatments for neurasthenia. Similarities are seen in several familiar diagnoses, including depression, chronic fatigue syndrome, and fibromyalgia. Through reviewing the trends of neurasthenia, modern doctors may learn more about the subtleties of the diagnostic process, as well as the patient-physician relationship. The goal is to learn from the past as it relates to current problems that may be related to the stress of modern living. The history of neurasthenia is presented as it relates to problems that may remain today.

Source: Overholser JC, Beale EE. Neurasthenia: Modern Malady or Historical Relic? J Nerv Ment Dis. 2019 Sep;207(9):731-739. doi: 10.1097/NMD.0000000000000943. https://www.ncbi.nlm.nih.gov/pubmed/31464984