EPIDEMIOLOGY OF INFLUENZA 501 



The recent epidemic has given much opportunity for bac- 

 teriological and serological study upon influenza bacilli from many 

 different types of lesion, from many different parts of the world. 

 The result of these studies has been confusing. Studies of Valentine 

 and Cooper 39 have shown that agglutination reactions do not in- 

 dicate hemogenicity of the influenza group. In a large number of 

 isolations and agglutinin reactions, they found that very few of 

 the strains fell into antigenically identical groups. Of ten autopsy 

 strains isolated by them, all strains seemed to be distinct. Of 

 seventy-three miscellaneous strains, no two strains were identical. 

 Two strains from different individuals were found to be identical, 

 but in a family in which there were six cases of influenza, all the 

 different races were distinct. It would seem that either influenza 

 bacilli were composed of an infinite number of antigenic varieties 

 or that the agglutinin reaction in these particular organisms, be- 

 cause of their small size, is not a suitable test for biological relation- 

 ship. For the present, the biological subdivision of the influenza 

 bacilli into well defined groups cannot be regarded as settled. 



Dr. Anna Williams 40 has recently studied hemoglobinophilic 

 bacilli isolated from the eye in cases of trachoma. She believes that 

 trachoma is probably caused by bacteria of this group. At first an 

 acute infection or acute conjunctivitis occurs. Later when chronic 

 productive inflammation supervenes the clinical picture is that of 

 trachoma. 



Experimental infection of animals reveals susceptibility only in 

 monkeys. Pfeiffer and Beck 41 produced influenza-like symptoms in 

 monkeys by rubbing a pure culture of the bacillus upon the un- 

 broken nasal mucosa. Intravenous inoculation in rabbits produced 

 severe symptoms, but the bacilli do not seem to proliferate in these 

 animals, the reaction probably being purely toxic. Cultures killed 

 with chloroform may produce severe transient toxic symptoms in 

 rabbits. 42 Immunity produced by an attack of influenza, if present 

 at all, is of very short duration. 



PSEUDO-INFLUENZA BACILLUS. In the broncho-pneumonic proc- 



39 Valentine and Cooper, Rep. 84, Dept. Health, City of N. Y., 1919, December. 

 ""/>/. Anna IVUHdnix, Ir.lcr. Congress of Hygiene and Demography, Washing- 

 ton, 1912. 



41 Pfeiffer mid Beck, Deut. mod. Woeh., xxi, 1893. 



42 Pfeiffer, loc cit. 



