STUDIES ON PNEUMONIC PLAGUE AND PLAGUE 

 IMMUNIZATION. 



III. INFLUENCE OF ATMOSPHERIC TEMPERATURE UPON THE 

 SPREAD OF PNEUMONIC PLAGUE. 



By Oscar Teague and M. A. Barber. 

 (From the Biological Laboratory, Bureau of Science, Manila, P. I.) 



In Manchuria, during the winter of 1910 to 1911, pneumonic 

 plague spread with such rapidity that within three months 

 50,000 people died of the disease. Except toward the close of 

 the epidemic, sanitary conditions were bad, the weather was 

 bitterly cold, and quarantine measures were inadequately en- 

 forced. In India, where sanitary conditions are, perhaps, equally 

 as bad, although there have been numerous isolated cases of 

 pneumonic plague during the past fifteen years (from 2 to 5 

 per cent of all plague cases), this type of the disease has not 

 assumed epidemic proportions. 



Why was there a rapid spread of the pneumonic type of 

 the disease in the one instance and a failure to spread in the 

 other? The most obvious difference in the two instances is 

 one of temperature, in the one case as low as 30° C. below zero 

 as compared to 30° C. above zero in the other. Can the failure 

 of pneumonic plague to spread in India be due to the high tem- 

 perature that prevails in that country? If we consider only 

 the direct action of the high temperature upon the plague bacilli, 

 this question must be answered in the negative; for the optimum 

 temperature for the cultivation of the plague bacilli upon arti- 

 ficial media is 30° C, which is approximately the temperature 

 to which they would be subjected in India. We believe, however, 

 that indirectly the temperature of the atmosphere is a factor of 

 vast importance in the spread or failure to spread of pneumonic 

 plague. 



It is quite generally accepted that infection in pneumonic 

 plague is due to the inhalation of plague bacilli and, as plague 

 bacilli are readily killed by drying, it is fair to assume that 

 infection is due to the inhalation of moist bacilli — the so-called 

 "droplet infection." In plague pneumonia, the mucous mem- 

 branes of the bronchi, trachea, larynx, and mouth are covered 

 with enormous numbers of plague bacilli. It follows that such 



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