Plague studies. IX. Epidemiology.

Epidemiological aspects of (a) bubonic plague and (b) primary pneumonic plague are discussed separately in this study. The cause, spread, and persistence of bubonic outbreaks are dealt with.IN THE CASE OF PRIMARY PNEUMONIC PLAGUE, THE AUTHOR SYSTEMATICALLY REVIEWS THE FACTORS INFLUENCING THE SPREAD OF THE DISEASE: climatic and social conditions, infectivity of the patients, immunity, and control measures. In discussing the cause of pneumonic plague outbreaks, the author deals with the possible influence of a special virulence of pneumonic strains, the role of the rodent and flea species involved, and the possibility of a pneumotropismus acquired by Pasteurella pestis.The periodicity (cyclical and secular) of bubonic plague epidemics is discussed with a view to the possible forecasting of future epidemics.The author indicates the influence of race, age, sex, and occupation on the incidence of both forms of the disease.