HISTORICAL ARTICLES Immunity as a Factor in the Epidemiology of Medieval Plague

The rise, disappearance, and demography of medieval plague remain mysterious. This paper reviewsthose features of plague immunity in animals and humans that might help explain these aspects of medieval plague. The absence of a focus of sylvatic plague in medieval Europe is postulated, while it is suggested that the susceptible population was much more varied both in terms of immunity and number of species than has been as-sumed. The sex, age, and regional variations in incidence of plague among humans are examined on the basis of primary and secondary historical sources. Nutritional factors, especially iron status, and cross-immunities with other diseases help provide an explana-tion of the observations in the literature. After an absence of seven centuries, plague struck Europe in 1348 with devastating force and pro-duced recurrent epidemics into the 18th century. Discussions of the demographic, economic, social, political, and even artistic implications of the dis-ease have produced an enormous historical litera