CHAPTER XXXVII 

 BACILLUS INFLUENZA AND CLOSELY RELATED BACTERIA 



THERE is no other epidemic disease which spreads over such enormous 

 territories, and with such speed, as influenza. Epidemics have been 

 numerous and reports of the disease, unquestionably recognizable, are 

 extant even from the most remote times. The last serious epidemic 

 occurred in the years 1889 to 1890, when the disease, spreading from 

 the East, traveled through Russia and, pandemically, attacked all of 

 Europe, then reached America, and eventually, having traveled east- 

 ward as well as westward from its point of origin, became prevalent 

 in China, Japan, Australia, and Africa. Hundreds of thousands were 

 attacked and the mortality of this epidemic was high. Its enormous 

 scope and the rapidity of its spread were facilitated probably by the 

 activity of modern international commerce. 



The character of the disease pointed so definitely to a bacterial 

 etiology that numerous attempts to isolate a specific microorganism 

 were, of course, made. Pfeiffer 1 finally, in 1892, described the bacillus 

 which is at present definitely recognized as the etiological factor of 

 influenza. 



Morphology and Staining. The bacillus of influenza' (Pfeiffer bacillus) 

 is an extremely small organism, about 0.5 micron long by 0.2 to 0.3 

 micron in width. They are somewhat irregular in length, but show 

 rounded ends. They rarely form chains. They are non-motile, and 

 do not form spores. 



Influenza bacilli stain less easily than do most other bacteria with 

 the usual anilin dyes, and are best demonstrated with 10 per cent 

 aqueous fuchsin (5 to 10 minutes), or with Loeffler's methylene-blue 

 (5 minutes). They are Gram-negative, giving up the anilin-gentian- 

 violet stain upon decolorization. Occasionally slight polar staining 

 may be noticed. Grouping, especially in thin smears of bronchial 

 secretion, is characteristic, in that the bacilli very rarely form threads 



1 Pfeiffer, Deut. med. Woch., ii, 1892; Zeit. f. Hyg., xiii, 1892; Pfeiffer und Beck, 

 Deut. med. Woch., xxi, 1893. 



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