938 DISKASKS CAUSED BY FILTRABLE VIRUS 



autopsy infections have been observed, but this mode of transmission 

 can, of course, play no role of importance in epidemic transmission. 

 It was suspected for a time that the sputum of typhus eases during 

 the stage of bronchitis might prove infectious and doctors and nurses 

 in Serbia for a time wore masks. But no clear evidence of any 

 such accident has been brought to our knowledge, and as far as 

 we know at the present time the louse is the only important means 

 by which the disease is conveyed. Indeed, our own experiences with 

 lice would persuade us that it is very difficult to absolutely exclude 

 the bite of a louse in an infected case, for lice may lodge on the 

 body in spite of the most rigid precautions and the bite of a louse 

 may be entirely painless and without noticeable reaction in many 

 individuals. 



There has been a considerable amount of discussion as to whether 

 the headlouse can transmit the disease as well as the body louse. 

 Goldberger and Anderson at one time believed this to be the case, 

 but there is still much uncertainty about it, and the weight of 

 evidence seems to be against it. As a matter of fact, in individuals 

 who are sufficiently lousy, specimens of the body louse variety may 

 be found in the hair of the head, neck and beard, on occasion. 



These facts explain clearly why typhus epidemics occur under 

 conditions of crowding, poverty and war ; why they spread so easily 

 from patient to doctor, and why they occur chiefly in cold countries 

 at times of the year when human beings are less apt to bathe and 

 keep clean and more likely to live close together in crowded quarters 

 for the sake of warmth. The louse, also, is not a tropical insect, 

 but thrives particularly in the cooler countries. In Mexico, for 

 instance, as Ricketts and Wilder found, there was little or no typhus 

 fever in the lowlands near the coast where lice were less common 

 than fleas, but typhus was most prevalent on the cooler plateau 

 country about the City of Mexico, where the population was much 

 more commonly infested with lice. 



The Serbian epidemic of 1915 was so severe that it interfered 

 materially with military activities, and it was probably because of 

 the epidemic that the Austrian Armies delayed their second attack 

 upon Serbia. A detailed description of this epidemic is found in 

 the article by Strong in the Red Cross Report referred to above. 

 Typhus appeared in the Serbian Army in October and November 

 of 1914, and it is said by Strong to have been introduced from 

 Albania. It is also believed that typhus was present in the Austrian 



