Myalgic Encephalomyelitis (ME) outbreaks can be modelled as an infectious disease: a mathematical reconsideration of the Royal Free Epidemic of 1955

ABSTRACTIn 1970, two clinicians, McEvedy and Beard [McEvedy CP, Beard AW (1970) Royal Free Epidemic of 1955: A Reconsideration The British Medical Journal 1: No. 5687: 7-11] re-analysed some of the case notes, and hypothesised that the Royal Free outbreak was epidemic hysteria. This hypothesis was the beginning of an entrenched belief that the disease at the Royal Free, and similar cluster outbreaks, were psychosomatic. This was to have a profound effect on the interpretation of the same illness for nearly 50 years as a presumptive psychosomatic, an interpretation that has lasted nearly 50 years. Methods:The 1927 Susceptible Infected Recovered (SIR) mathematical model [Kermack WO, McKendrick AG. Contribution to the mathematical theory of epidemics. Proc Royal Soc London. 1927;772:701–721] for the transmission of disease has been used to examine the published admission data from the Royal Free Hospital. for the purpose of finding out if the disease had the characteristics of a contagious disease. Similar cluster outbreaks have also been modelled to assess whether they have similar characteristics to the Royal Free outbreak. Results:Using the 1927 Susceptible Infected Recovered (SIR) model [Kermack WO, McKendrick AG. Contribution to the mathematical theory of epidemics. Proc Royal Soc London. 1927;772:701–721] for the transmission of disease, we show that the epidemic of a disease of an unknown aetiology at the Royal Free Hospital in 1955, and other similar twentieth-century outbreaks, have the characteristics of a communicable disease. The disease causing the Royal Free outbreak was given the name ‘Benign Myalgic Encephalomyelitis' by Acheson [A new clinical entity? Lancet. 1956;1:789–790] in 1956, now identified as ME. Conclusions:By showing that the Royal Free and other ME attributed outbreaks fit the SIR disease model, we demonstrate that the McEvedy and Beard hysteria hypothesis is mathematically incorrect. The ensuing management of the treatment of ME/CFS-like conditions evolving from that, now mathematically improbable belief may need to be re-evaluated.