“The Anatomy of the Epidemic”: Contested Illness Outbreaks in US Medicine and Public Health, 1934-2020

Abstract

A symptom complex marked by fatigue, muscle weakness, and brain fog has puzzled patients and clinicians for nearly a century, attracting several contested explanations from the psychosomatic to the post-viral. These contestations affect not just the perceived legitimacy of patient suffering, but the legitimacy of the illness and of biomedicine itself, which may be at risk of delegitimization when it cannot locate the cause of people’s suffering. Throughout the twentieth century, these symptoms cropped up in the context of outbreaks of an infectious disease resembling poliomyelitis. The first set of outbreaks took place between 1934-1956 before public health interest waned. In the 1980s outbreaks reemerged and were connected to other viral threats like Epstein-Barr virus, but by then the condition had spread far beyond the local outbreak context and has persisted through to the present problem of long COVID. Although the condition has not been deadly, these episodes often led to long-term disability with a prolonged, relapsing course. With the rise of an epidemiological infrastructure shaped by the fight against polio, organizations like the Yale Poliomyelitis Study Unit, the U.S. Public Health Service, and the CDC's Epidemic Intelligence Service investigated these mysterious outbreaks from 1934 to 1956. Despite thorough investigation, no pathogen was identified. The illness, eventually named epidemic neuromyasthenia or myalgic encephalomyelitis, defied dominant germ-theory frameworks. Lacking microbial evidence, researchers increasingly attributed it to psychosomatic causes or mass hysteria—especially given the global rise of similar outbreaks amid stress, schooling pressures, and Cold War anxieties about crowd behavior and social contagion. As outbreaks waned by the 1970s, the mass hysteria narrative gained further traction. In the 1980s, attention returned to viral theories as doctors began to publish reports of chronic symptoms linked to Epstein-Barr virus. The “chronic Epstein-Barr virus disease” mirrored earlier syndromes, culminating in a high-profile CDC investigation in Lake Tahoe. The CDC ultimately labeled the condition “chronic fatigue syndrome” and dismissed a direct EBV link, initiating decades of controversy over its legitimacy. CFS became emblematic of “contested illnesses”—conditions with real suffering but unclear etiology. In the COVID-19 pandemic, many people developed persistent symptoms post-infection, now called “long COVID,” again echoing past episodes. Long COVID has spurred more medical attention and scientific research on these kinds of conditions than ever before, with the potential to change how science and medicine can help patients. This thesis explores how the epidemiological context—shaped by scientific paradigms, public health institutions, and cultural narratives—has influenced the medical and social treatment of diseases with diffuse, disabling symptoms and uncertain viral origins. It also asks how these conditions went from novel public health threats to marginal, stigmatized, and illegitimate conditions, and back to novel public health threats once again with long COVID.