adapt to living with me/cfs." some people who improve need to manage their activities in order to prevent relapse. children and teenagers are more likely to recover or improve than adults. a 2005 systematic review found that for untreated cfs, "the median full recovery rate was 5% (range 0–31%) and the median proportion of patients who improved during follow-up was 39.5% (range 8–63%)," and that 8 to 30% of patients were able to return to work. age at onset, a longer duration of follow-up, less fatigue severity at baseline, and other factors were occasionally, but non consistently, related to outcome. another review found that children have a better prognosis than adults, with 54–94% having recovered by follow-up, compared to less than 10% of adults returning to pre-illness levels of functioning. epidemiology incidence rates by age and sex, from a 2014 study in norway reported prevalence rates vary widely depending on how cfs/me is defined and diagnosed. based on the 1994 cdc diagnostic criteria, the global prevalence rate for cfs is 0.89%. in comparison, estimates using the 1988 cdc "holmes" criteria and 2003 canadian criteria for me produced an incidence rate of only 0.17%. between 836,000 and 2.5 million americans have me/cfs, but that 84-91% of these are undiagnosed,: 1 and over 250,000 people in england and wales are estimated to be affected. the worldwide prevalence is 17 and 24 million. females are diagnosed about 1.5 to 2.0 times more often with cfs than males. an estimated 0.5% of children have cfs, and more adolescents are affected with the illness than younger children.: 182 the incidence rate according to age has two peaks, one at 10–19 and another at 30–39 years, and the rate of prevalence is highest between ages 40 and 60. history main article: history of chronic fatigue syndrome myalgic encephalomyelitis from 1934 onwards, outbreaks of a previously unknown illness began to be recorded by doctors. initially considered to be occurrences of poliomyelitis, the illness was subsequently referred to as "epidemic neuromyasthenia". in the 1950s, the term "benign myalgic encephalomyelitis" was used in relation to a comparable outbreak at the royal free hospital in london. the descriptions of each outbreak were varied, but included symptoms of malaise, tender lymph nodes, sore throat, pain, and signs of encephalomyelitis. the cause of the condition was not identified, although it appeared to be infectious, and the term "benign myalgic encephalomyelitis" was chosen to reflect the lack of mortality, the severe muscular pains, symptoms suggesting damage to the nervous system, and to the presumed inflammatory nature of the disorder. björn sigurðsson disapproved of the name, stating that the illness is rarely benign, does not always cause muscle pain, and is possibly never encephalomyelitic. the syndrome appeared in sporadic as well as epidemic cases. in 1969, benign myalgic encephalomyelitis appeared as an entry to the international classification of diseases under diseases of the nervous system. in 1986, ramsay published the first diagnostic criteria for me, in which the condition was characterized by: 1) muscle fatiguability in which, even after minimal physical effort, three or more days elapse before full muscle power is restored; 2) extraordinary variability or fluctuation of symptoms, even in the course of one day; and 3) chronicity. by 1988, the continued work of ramsay had demonstrated that, although the disease rarely resulted in mortality, it was often severely disabling.: 28–29 because of this, ramsay proposed that the prefix "benign" be dropped. chronic fatigue syndrome in the mid-1980s, two large outbreaks of an illness that resembled mononucleosis drew national attention in the united states. located in nevada and new york, the outbreaks involved an illness characterized by "chronic or recurrent debilitating fatigue, and various combinations of other symptoms, including a sore throat, lymph node pain and tenderness, headache, myalgia, and arthralgias". an initial link to the epstein-barr virus had the illness acquire the name "chronic epstein-barr virus syndrome".: 29 in 1987, the cdc convened a working group to reach a consensus on the clinical features of the illness. the working group concluded that cfs was not new, and that the many different names given to it previously reflected widely differing concepts of the illness's cause and epidemiology. the cdc working group chose "chronic fatigue syndrome" as a more neutral and inclusive name for the illness, but noted that "myalgic encephalomyelitis" was widely accepted in other parts of the world. in 1988, the first definition of cfs was published. although the cause of the illness remained unknown, several attempts were made to update this definition, most notably in 1994. the most widely referenced diagnostic criteria and definition of cfs for research and clinical purposes were published in 1994 by the cdc. in 2006, the cdc commenced a national program to educate the american public and health-care professionals about cfs. other medical terms a range of both theorised and confirmed medical entities and naming conventions have appeared historically in the medical literature dealing with me and cfs. these include: epidemic neuromyasthenia was a term used for outbreaks with symptoms resembling poliomyelitis. iceland disease and akureyri disease were synonymous terms used for an outbreak of fatigue symptoms in iceland. low natural killer syndrome, a term used mainly in japan, reflected research showing diminished in vitro activity of natural killer cells isolated from patients. neurasthenia had been proposed as a historical diagnosis that occupied a similar medical and cultural space to cfs. royal free disease was named after the historically significant outbreak in 1955 at the royal free hospital used as an informal synonym for "benign myalgic encephalomyelitis". tapanui flu was a term commonly used in new zealand, deriving from the name of a town, tapanui, where numerous people had the syndrome. society and culture presentation of a petition to the national assembly for wales relating to me support in south east wales naming many names have been proposed for the illness. currently, the most commonly used are "chronic fatigue syndrome", "myalgic encephalomyelitis", and the umbrella term "me/cfs". reaching consensus on a name is challenging because the cause and pathology remain unknown.: 29–30 the term "chronic fatigue syndrome" has been criticized by some patients as being both stigmatizing and trivializing, and which in turn prevents the illness from being seen as a serious health problem that deserves appropriate research. while many patients prefer "myalgic encephalomyelitis", which they believe better reflects the medical nature of the illness, there is resistance amongst some clinicians toward the use of myalgic encephalomyelitis on the grounds that the inflammation of the central nervous system (myelitis) implied by the term has not been demonstrated. a 2015 report from the institute of medicine recommended the illness be renamed "systemic exertion intolerance disease", (seid), and suggested new diagnostic criteria, proposing post-exertional malaise (pem), impaired function, and sleep problems are core symptoms of me/cfs. additionally, they described cognitive impairment and orthostatic intolerance as distinguishing symptoms from other fatiguing illnesses. economic impact economic costs due to cfs are "significant." a 2021 paper by leonard jason and arthur mirin estimated the impact in the us to be $36-51 billion per year, or $31,592 to $41,630 per person, considering both lost wages and healthcare costs. the cdc estimated direct healthcare costs alone at $9-14 billion annually. a 2017 estimate for the annual economic burden in the united kingdom was £3.3 billion. awareness day 12 may is designated as me/cfs international awareness day. the day is observed so that stakeholders have an occasion to improve the knowledge of "the public, policymakers, and health-care professionals about the symptoms, diagnosis, and treatment of me/cfs, as well as the need for a better understanding of this complex illness." it was chosen because it is the birthday of florence nightingale, who had an illness appearing similar to me/cfs or fibromyalgia. doctor–patient relations people with cfs face stigma in healthcare settings, and doctors may have trouble managing an illness that lacks a clear cause or treatment.: 30 there has been much disagreement over proposed causes, diagnosis, and treatment of the illness. some doctors believe it is psychological.: 234 most patients are convinced their illness is physical instead, straining doctor-patient relationships. clinicians may be unfamiliar with cfs, as it is often not covered in medical school. due to this unfamiliarity, patients may go undiagnosed for years,: 2861 : 1 or be misdiagnosed with mental conditions.: 2871 a substantial portion of doctors are uncertain about how to diagnose or manage cfs. in a 2006 survey of gps in southwest england, 75% accepted it as a "recognisable clinical entity," but 48% did not feel confident in diagnosing it, and 41% in managing it. the nam report refers to cfs as "stigmatized," and the majority of patients report negative healthcare experiences.: 30 these patients may feel that their doctor inappropriately calls their illness psychological or doubts the severity of their symptoms. they may also feel forced to prove that they are legitimately ill. some may be given outdated treatments that provoke symptoms or assume their illness is due to unhelpful thoughts and deconditioning.: 25 : 2871 in a 2009 survey, only 35% of patients considered their physicians experienced with cfs and only 23% thought their doctors knew enough to treat it. blood donation in 2010, several national blood banks adopted measures to discourage or prohibit individuals diagnosed with cfs from donating blood, based on concern following the 2009 claim of a link between cfs and a retrovirus which was subsequently shown to be unfounded. organizations adopting these or similar measures included the canadian blood services, the new zealand blood service, the australian red cross blood service and the american association of blood banks. in november 2010, the uk national blood service permanently deferred me/cfs patients from donating blood to prevent potential harm to the donor. donation policy in the uk now states, "the condition is relapsing by nature and donation may make symptoms worse, or provoke a relapse in an affected individual." controversy main article: controversies related to chronic fatigue syndrome much contention has arisen over the cause, pathophysiology, nomenclature, and diagnostic criteria of cfs. historically, many professionals within the medical community were unfamiliar with cfs, or did not recognize it as a real condition; nor did agreement exist on its prevalence or seriousness. some people with cfs reject any psychological component. in 1970, two british psychiatrists, mcevedy and beard, reviewed the case notes of 15 outbreaks of benign myalgic encephalomyelitis and concluded that it was caused by mass hysteria on the part of patients, or altered medical perception of the attending physicians. their conclusions were based on previous studies that found many normal physical test results, a lack of a discernible cause, and a higher prevalence of the illness in females. consequently, the authors recommended that the disease should be renamed "myalgia nervosa". this perspective was rejected in a series of case studies by melvin ramsay and other staff of the royal free hospital, the center of a significant outbreak. the psychological hypothesis posed by mcevedy and beard created great controversy, and convinced a generation of health professionals in the uk that this could be a plausible explanation for the condition, resulting in neglect by many medical specialties. the specialty that did take a major interest in the illness was psychiatry. because of the controversy, sociologists hypothesized that stresses of modern living might be a cause of the illness, while some in the media used the term "yuppie flu" and called it a disease of the middle class. people with disabilities from cfs were often not believed and were accused of being malingerers. the november 1990 issue of newsweek ran a cover story on cfs, which although supportive of an organic cause of the illness, also featured the term 'yuppie flu', reflecting the stereotype that cfs mainly affected yuppies. the implication was that cfs is a form of burnout. the term 'yuppie flu' is considered offensive by both patients and clinicians. in 2009, the journal science published a study that identified the xmrv retrovirus in a population of people with cfs. other studies failed to reproduce this finding, and in 2011, the editor of science formally retracted its xmrv paper while the proceedings of the national academy of sciences similarly retracted a 2010 paper which had appeared to support the finding of a connection between xmrv and cfs. united kingdom the lack of research funding